SELinuxにはじかれていろいろできない場合の対処法。
よくやること
・getenforceでSELinuxの状態確認
・/var/log/audit/audit.logの確認
・ls -Z でコンテキストの確認
・audit2allow /var/log/audit/audit.logで、対処方法の確認
・setseboolで、ルールの有効無効の設定
・semoduleでポリシー設定
ポリシー設定方法
teファイルにポリシーを記述
# mymod.te
module mymod 1.0;
require {
type httpd_t;
type clamscan_exec_t;
type clamd_var_lib_t;
class file { getattr read open };
class dir { read getattr open search };
}
#============= httpd_t ==============
allow httpd_t clamscan_exec_t:file { getattr read open };
allow httpd_t clamd_var_lib_t:dir { read getattr open search };
allow httpd_t clamd_var_lib_t:file { read getattr open };
/usr/share/selinux/develのMakefileでmakeし、ppファイルを作成
semoduleでモジュールをインストール
semodule -i mymod.pp
SELinuxをいったんPermissiveにして、auditlogにある程度情報を集め、その後audit2allowでポリシー作成、ポリシー適用、の流れが一番楽かも。
2014年6月12日木曜日
2014年6月6日金曜日
linux上でfioを用いてIOPSを計測
IOPSが計測したい、と思いつき、調べてみるとfioというツールで簡単に計測出来るらしい。
というわけで計測してみた。
手元のCloudNで。OSはCent6.3。
fioはyumでinstall可能。
設定ファイルを作成し、引数で指定して実行する。
---write.fio---
[global]
ioengine=libaio
direct=1
invalidate=1
group_reporting
directory=/home
filename=test.bin
runtime=60
[Rand-Write-4k-qd32]
readwrite=randwrite
size=4G
bs=4k
iodepth=32
numjobs=1
書き込み性能の計測。
> fio write.fio
Rand-Write-4k-qd32: (g=0): rw=randwrite, bs=4K-4K/4K-4K/4K-4K, ioengine=libaio, iodepth=32
fio-2.0.13
Starting 1 process
Rand-Write-4k-qd32: Laying out IO file(s) (1 file(s) / 4096MB)
Jobs: 1 (f=1): [w] [1.6% done] [0K/1036K/0K /s] [0 /259 /0 iops] [eta 01h:04m:23s]
Rand-Write-4k-qd32: (groupid=0, jobs=1): err= 0: pid=6399: Fri Jun 6 16:47:56 2014
write: io=65324KB, bw=1087.5KB/s, iops=271 , runt= 60069msec
slat (usec): min=9 , max=147169 , avg=83.39, stdev=2505.22
clat (usec): min=901 , max=319079 , avg=117614.32, stdev=60605.75
lat (usec): min=939 , max=319103 , avg=117698.36, stdev=60659.33
clat percentiles (msec):
| 1.00th=[ 16], 5.00th=[ 26], 10.00th=[ 37], 20.00th=[ 56],
| 30.00th=[ 75], 40.00th=[ 97], 50.00th=[ 120], 60.00th=[ 139],
| 70.00th=[ 157], 80.00th=[ 176], 90.00th=[ 198], 95.00th=[ 212],
| 99.00th=[ 251], 99.50th=[ 265], 99.90th=[ 293], 99.95th=[ 306],
| 99.99th=[ 318]
bw (KB/s) : min= 631, max= 1466, per=100.00%, avg=1090.50, stdev=189.22
lat (usec) : 1000=0.01%
lat (msec) : 2=0.01%, 4=0.05%, 10=0.06%, 20=2.65%, 50=14.48%
lat (msec) : 100=23.94%, 250=57.78%, 500=1.03%
cpu : usr=0.16%, sys=0.75%, ctx=6276, majf=0, minf=22
IO depths : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.1%, 32=99.8%, >=64=0.0%
submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.1%, 64=0.0%, >=64=0.0%
issued : total=r=0/w=16331/d=0, short=r=0/w=0/d=0
Run status group 0 (all jobs):
WRITE: io=65324KB, aggrb=1087KB/s, minb=1087KB/s, maxb=1087KB/s, mint=60069msec, maxt=60069msec
Disk stats (read/write):
dm-0: ios=0/17652, merge=0/0, ticks=0/2025293, in_queue=2030659, util=99.92%, aggrios=0/16405, aggrmerge=0/1259, aggrticks=0/1913289, aggrin_queue=1913280, aggrutil=99.89%
vda: ios=0/16405, merge=0/1259, ticks=0/1913289, in_queue=1913280, util=99.89%
書き込みIOPS271。
続いて読み込み。
----read.fio----
[global]
ioengine=libaio
direct=1
invalidate=1
group_reporting
directory=/home
filename=test.bin
runtime=60
[Rand-Read-4k-qd32]
readwrite=randread
size=4G
bs=4k
iodepth=32
numjobs=1
>fio read.fio
Rand-Read-4k-qd32: (g=0): rw=randread, bs=4K-4K/4K-4K/4K-4K, ioengine=libaio, iodepth=32
fio-2.0.13
Starting 1 process
Jobs: 1 (f=1): [r] [83.3% done] [773.6M/0K/0K /s] [198K/0 /0 iops] [eta 00m:02s]
Rand-Read-4k-qd32: (groupid=0, jobs=1): err= 0: pid=6416: Fri Jun 6 16:53:21 2014
read : io=4096.0MB, bw=425256KB/s, iops=106314 , runt= 9863msec
slat (usec): min=2 , max=441 , avg= 3.41, stdev= 3.71
clat (usec): min=0 , max=109809 , avg=296.16, stdev=1518.26
lat (usec): min=4 , max=109820 , avg=299.88, stdev=1520.24
clat percentiles (usec):
| 1.00th=[ 137], 5.00th=[ 139], 10.00th=[ 141], 20.00th=[ 143],
| 30.00th=[ 147], 40.00th=[ 153], 50.00th=[ 157], 60.00th=[ 157],
| 70.00th=[ 159], 80.00th=[ 167], 90.00th=[ 177], 95.00th=[ 181],
| 99.00th=[ 4640], 99.50th=[ 9280], 99.90th=[24448], 99.95th=[30592],
| 99.99th=[42240]
bw (KB/s) : min= 9940, max=840800, per=96.25%, avg=409291.58, stdev=392536.90
lat (usec) : 2=0.01%, 10=0.02%, 20=0.01%, 50=0.01%, 100=0.03%
lat (usec) : 250=98.17%, 500=0.19%, 750=0.02%, 1000=0.01%
lat (msec) : 2=0.04%, 4=0.38%, 10=0.67%, 20=0.28%, 50=0.17%
lat (msec) : 100=0.01%, 250=0.01%
cpu : usr=14.73%, sys=44.41%, ctx=10779, majf=0, minf=56
IO depths : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.1%, 32=100.0%, >=64=0.0%
submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.1%, 64=0.0%, >=64=0.0%
issued : total=r=1048576/w=0/d=0, short=r=0/w=0/d=0
Run status group 0 (all jobs):
READ: io=4096.0MB, aggrb=425256KB/s, minb=425256KB/s, maxb=425256KB/s, mint=9863msec, maxt=9863msec
Disk stats (read/write):
dm-0: ios=16331/10, merge=0/0, ticks=149442/415, in_queue=149857, util=48.35%, aggrios=16331/4, aggrmerge=0/7, aggrticks=149418/114, aggrin_queue=149521, aggrutil=47.25%
vda: ios=16331/4, merge=0/7, ticks=149418/114, in_queue=149521, util=47.25%
10万・・・？
というわけで計測してみた。
手元のCloudNで。OSはCent6.3。
fioはyumでinstall可能。
設定ファイルを作成し、引数で指定して実行する。
---write.fio---
[global]
ioengine=libaio
direct=1
invalidate=1
group_reporting
directory=/home
filename=test.bin
runtime=60
[Rand-Write-4k-qd32]
readwrite=randwrite
size=4G
bs=4k
iodepth=32
numjobs=1
書き込み性能の計測。
> fio write.fio
Rand-Write-4k-qd32: (g=0): rw=randwrite, bs=4K-4K/4K-4K/4K-4K, ioengine=libaio, iodepth=32
fio-2.0.13
Starting 1 process
Rand-Write-4k-qd32: Laying out IO file(s) (1 file(s) / 4096MB)
Jobs: 1 (f=1): [w] [1.6% done] [0K/1036K/0K /s] [0 /259 /0 iops] [eta 01h:04m:23s]
Rand-Write-4k-qd32: (groupid=0, jobs=1): err= 0: pid=6399: Fri Jun 6 16:47:56 2014
write: io=65324KB, bw=1087.5KB/s, iops=271 , runt= 60069msec
slat (usec): min=9 , max=147169 , avg=83.39, stdev=2505.22
clat (usec): min=901 , max=319079 , avg=117614.32, stdev=60605.75
lat (usec): min=939 , max=319103 , avg=117698.36, stdev=60659.33
clat percentiles (msec):
| 1.00th=[ 16], 5.00th=[ 26], 10.00th=[ 37], 20.00th=[ 56],
| 30.00th=[ 75], 40.00th=[ 97], 50.00th=[ 120], 60.00th=[ 139],
| 70.00th=[ 157], 80.00th=[ 176], 90.00th=[ 198], 95.00th=[ 212],
| 99.00th=[ 251], 99.50th=[ 265], 99.90th=[ 293], 99.95th=[ 306],
| 99.99th=[ 318]
bw (KB/s) : min= 631, max= 1466, per=100.00%, avg=1090.50, stdev=189.22
lat (usec) : 1000=0.01%
lat (msec) : 2=0.01%, 4=0.05%, 10=0.06%, 20=2.65%, 50=14.48%
lat (msec) : 100=23.94%, 250=57.78%, 500=1.03%
cpu : usr=0.16%, sys=0.75%, ctx=6276, majf=0, minf=22
IO depths : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.1%, 32=99.8%, >=64=0.0%
submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.1%, 64=0.0%, >=64=0.0%
issued : total=r=0/w=16331/d=0, short=r=0/w=0/d=0
Run status group 0 (all jobs):
WRITE: io=65324KB, aggrb=1087KB/s, minb=1087KB/s, maxb=1087KB/s, mint=60069msec, maxt=60069msec
Disk stats (read/write):
dm-0: ios=0/17652, merge=0/0, ticks=0/2025293, in_queue=2030659, util=99.92%, aggrios=0/16405, aggrmerge=0/1259, aggrticks=0/1913289, aggrin_queue=1913280, aggrutil=99.89%
vda: ios=0/16405, merge=0/1259, ticks=0/1913289, in_queue=1913280, util=99.89%
書き込みIOPS271。
続いて読み込み。
----read.fio----
[global]
ioengine=libaio
direct=1
invalidate=1
group_reporting
directory=/home
filename=test.bin
runtime=60
[Rand-Read-4k-qd32]
readwrite=randread
size=4G
bs=4k
iodepth=32
numjobs=1
>fio read.fio
Rand-Read-4k-qd32: (g=0): rw=randread, bs=4K-4K/4K-4K/4K-4K, ioengine=libaio, iodepth=32
fio-2.0.13
Starting 1 process
Jobs: 1 (f=1): [r] [83.3% done] [773.6M/0K/0K /s] [198K/0 /0 iops] [eta 00m:02s]
Rand-Read-4k-qd32: (groupid=0, jobs=1): err= 0: pid=6416: Fri Jun 6 16:53:21 2014
read : io=4096.0MB, bw=425256KB/s, iops=106314 , runt= 9863msec
slat (usec): min=2 , max=441 , avg= 3.41, stdev= 3.71
clat (usec): min=0 , max=109809 , avg=296.16, stdev=1518.26
lat (usec): min=4 , max=109820 , avg=299.88, stdev=1520.24
clat percentiles (usec):
| 1.00th=[ 137], 5.00th=[ 139], 10.00th=[ 141], 20.00th=[ 143],
| 30.00th=[ 147], 40.00th=[ 153], 50.00th=[ 157], 60.00th=[ 157],
| 70.00th=[ 159], 80.00th=[ 167], 90.00th=[ 177], 95.00th=[ 181],
| 99.00th=[ 4640], 99.50th=[ 9280], 99.90th=[24448], 99.95th=[30592],
| 99.99th=[42240]
bw (KB/s) : min= 9940, max=840800, per=96.25%, avg=409291.58, stdev=392536.90
lat (usec) : 2=0.01%, 10=0.02%, 20=0.01%, 50=0.01%, 100=0.03%
lat (usec) : 250=98.17%, 500=0.19%, 750=0.02%, 1000=0.01%
lat (msec) : 2=0.04%, 4=0.38%, 10=0.67%, 20=0.28%, 50=0.17%
lat (msec) : 100=0.01%, 250=0.01%
cpu : usr=14.73%, sys=44.41%, ctx=10779, majf=0, minf=56
IO depths : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.1%, 32=100.0%, >=64=0.0%
submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.1%, 64=0.0%, >=64=0.0%
issued : total=r=1048576/w=0/d=0, short=r=0/w=0/d=0
Run status group 0 (all jobs):
READ: io=4096.0MB, aggrb=425256KB/s, minb=425256KB/s, maxb=425256KB/s, mint=9863msec, maxt=9863msec
Disk stats (read/write):
dm-0: ios=16331/10, merge=0/0, ticks=149442/415, in_queue=149857, util=48.35%, aggrios=16331/4, aggrmerge=0/7, aggrticks=149418/114, aggrin_queue=149521, aggrutil=47.25%
vda: ios=16331/4, merge=0/7, ticks=149418/114, in_queue=149521, util=47.25%
10万・・・？
UnixBenchでCloudNのComputeFlatをベンチマーク
NTTComのクラウドサービス、CloudNのComputeFlatを契約することがあったので、せっかくの機会にとUnixBenchでベンチマーク。プランは1CPU2GBです。
以下結果。
========================================================================
BYTE UNIX Benchmarks (Version 5.1.3)
System: suishin: GNU/Linux
OS: GNU/Linux -- 2.6.32-279.el6.x86_64 -- #1 SMP Fri Jun 22 12:19:21 UTC 2012
Machine: x86_64 (x86_64)
Language: en_US.utf8 (charmap="UTF-8", collate="UTF-8")
CPU 0: QEMU Virtual CPU version (cpu64-rhel6) (3990.4 bogomips)
x86-64, MMX, Physical Address Ext, SYSCALL/SYSRET
15:47:15 up 1 day, 21:12, 1 user, load average: 0.60, 0.21, 0.06; runlevel 3
------------------------------------------------------------------------
Benchmark Run: Fri Jun 06 2014 15:47:15 - 16:15:37
1 CPU in system; running 1 parallel copy of tests
Dhrystone 2 using register variables 28617114.2 lps (10.0 s, 7 samples)
Double-Precision Whetstone 3017.1 MWIPS (9.7 s, 7 samples)
Execl Throughput 3089.6 lps (29.9 s, 2 samples)
File Copy 1024 bufsize 2000 maxblocks 653774.6 KBps (30.0 s, 2 samples)
File Copy 256 bufsize 500 maxblocks 192359.8 KBps (30.0 s, 2 samples)
File Copy 4096 bufsize 8000 maxblocks 1755114.1 KBps (30.0 s, 2 samples)
Pipe Throughput 1331340.7 lps (10.0 s, 7 samples)
Pipe-based Context Switching 235541.7 lps (10.0 s, 7 samples)
Process Creation 8824.3 lps (30.0 s, 2 samples)
Shell Scripts (1 concurrent) 4037.8 lpm (60.0 s, 2 samples)
Shell Scripts (8 concurrent) 563.4 lpm (60.1 s, 2 samples)
System Call Overhead 2082605.7 lps (10.0 s, 7 samples)
System Benchmarks Index Values BASELINE RESULT INDEX
Dhrystone 2 using register variables 116700.0 28617114.2 2452.2
Double-Precision Whetstone 55.0 3017.1 548.6
Execl Throughput 43.0 3089.6 718.5
File Copy 1024 bufsize 2000 maxblocks 3960.0 653774.6 1650.9
File Copy 256 bufsize 500 maxblocks 1655.0 192359.8 1162.3
File Copy 4096 bufsize 8000 maxblocks 5800.0 1755114.1 3026.1
Pipe Throughput 12440.0 1331340.7 1070.2
Pipe-based Context Switching 4000.0 235541.7 588.9
Process Creation 126.0 8824.3 700.3
Shell Scripts (1 concurrent) 42.4 4037.8 952.3
Shell Scripts (8 concurrent) 6.0 563.4 939.0
System Call Overhead 15000.0 2082605.7 1388.4
========
System Benchmarks Index Score 1098.1
ちょっと低いかな・・・。
ただ、AWSと比べるとかなり性能が良い感じですね。
以下結果。
========================================================================
BYTE UNIX Benchmarks (Version 5.1.3)
System: suishin: GNU/Linux
OS: GNU/Linux -- 2.6.32-279.el6.x86_64 -- #1 SMP Fri Jun 22 12:19:21 UTC 2012
Machine: x86_64 (x86_64)
Language: en_US.utf8 (charmap="UTF-8", collate="UTF-8")
CPU 0: QEMU Virtual CPU version (cpu64-rhel6) (3990.4 bogomips)
x86-64, MMX, Physical Address Ext, SYSCALL/SYSRET
15:47:15 up 1 day, 21:12, 1 user, load average: 0.60, 0.21, 0.06; runlevel 3
------------------------------------------------------------------------
Benchmark Run: Fri Jun 06 2014 15:47:15 - 16:15:37
1 CPU in system; running 1 parallel copy of tests
Dhrystone 2 using register variables 28617114.2 lps (10.0 s, 7 samples)
Double-Precision Whetstone 3017.1 MWIPS (9.7 s, 7 samples)
Execl Throughput 3089.6 lps (29.9 s, 2 samples)
File Copy 1024 bufsize 2000 maxblocks 653774.6 KBps (30.0 s, 2 samples)
File Copy 256 bufsize 500 maxblocks 192359.8 KBps (30.0 s, 2 samples)
File Copy 4096 bufsize 8000 maxblocks 1755114.1 KBps (30.0 s, 2 samples)
Pipe Throughput 1331340.7 lps (10.0 s, 7 samples)
Pipe-based Context Switching 235541.7 lps (10.0 s, 7 samples)
Process Creation 8824.3 lps (30.0 s, 2 samples)
Shell Scripts (1 concurrent) 4037.8 lpm (60.0 s, 2 samples)
Shell Scripts (8 concurrent) 563.4 lpm (60.1 s, 2 samples)
System Call Overhead 2082605.7 lps (10.0 s, 7 samples)
System Benchmarks Index Values BASELINE RESULT INDEX
Dhrystone 2 using register variables 116700.0 28617114.2 2452.2
Double-Precision Whetstone 55.0 3017.1 548.6
Execl Throughput 43.0 3089.6 718.5
File Copy 1024 bufsize 2000 maxblocks 3960.0 653774.6 1650.9
File Copy 256 bufsize 500 maxblocks 1655.0 192359.8 1162.3
File Copy 4096 bufsize 8000 maxblocks 5800.0 1755114.1 3026.1
Pipe Throughput 12440.0 1331340.7 1070.2
Pipe-based Context Switching 4000.0 235541.7 588.9
Process Creation 126.0 8824.3 700.3
Shell Scripts (1 concurrent) 42.4 4037.8 952.3
Shell Scripts (8 concurrent) 6.0 563.4 939.0
System Call Overhead 15000.0 2082605.7 1388.4
========
System Benchmarks Index Score 1098.1
ちょっと低いかな・・・。
ただ、AWSと比べるとかなり性能が良い感じですね。
2013年11月15日金曜日
仮想化に関する SQL Server 2012 のライセンス
SQL Server 2012のライセンスに関するメモ
各エディションで2種類のライセンスモデルが利用可能
・コアベース
・サーバー/CAL
コアベースでは、1仮想プロセッサにつき1コアとみなされる。（仮想サーバに4コア割り当てると4コアライセンス必要)
ライセンスモビリティ（サーバーのライブマイグレーションへの対応）に関しては、SAが適用されている場合にのみ許可される。
各エディションで2種類のライセンスモデルが利用可能
・コアベース
・サーバー/CAL
コアベースでは、1仮想プロセッサにつき1コアとみなされる。（仮想サーバに4コア割り当てると4コアライセンス必要)
ライセンスモビリティ（サーバーのライブマイグレーションへの対応）に関しては、SAが適用されている場合にのみ許可される。
2012年5月31日木曜日
RFC 1813 日本語訳
NFSv3の日本語訳がなかったので翻訳中。まだほぼ機械翻訳です。
原文はこのへんをどうぞ
Network Working Group B. Callaghan
Request for Comments: 1813 B. Pawlowski
Category: Informational P. Staubach
Sun Microsystems, Inc.
June 1995
NFS Version 3 Protocol Specification
Status of this Memo
This memo provides information for the Internet community.
This memo does not specify an Internet standard of any kind.
Distribution of this memo is unlimited.
IESG Note
Internet Engineering Steering Group comment: please note that
the IETF is not involved in creating or maintaining this
specification. This is the significance of the specification
not being on the standards track.
Abstract
This paper describes the NFS version 3 protocol. This paper is
provided so that people can write compatible implementations.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Scope of the NFS version 3 protocol . . . . . . . . . . 4
1.2 Useful terms . . . . . . . . . . . . . . . . . . . . . . 5
1.3 Remote Procedure Call . . . . . . . . . . . . . . . . . 5
1.4 External Data Representation . . . . . . . . . . . . . . 5
1.5 Authentication and Permission Checking . . . . . . . . . 7
1.6 Philosophy . . . . . . . . . . . . . . . . . . . . . . . 8
1.7 Changes from the NFS version 2 protocol . . . . . . . . 11
2. RPC Information . . . . . . . . . . . . . . . . . . . . . 14
2.1 Authentication . . . . . . . . . . . . . . . . . . . . . 14
2.2 Constants . . . . . . . . . . . . . . . . . . . . . . . 14
2.3 Transport address . . . . . . . . . . . . . . . . . . . 14
2.4 Sizes . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.5 Basic Data Types . . . . . . . . . . . . . . . . . . . . 15
2.6 Defined Error Numbers . . . . . . . . . . . . . . . . . 17
3. Server Procedures . . . . . . . . . . . . . . . . . . . . 27
3.1 General comments on attributes . . . . . . . . . . . . . 29
3.2 General comments on filenames . . . . . . . . . . . . . 30
3.3.0 NULL: Do nothing . . . . . . . . . . . . . . . . . . . . 31
3.3.1 GETATTR: Get file attributes . . . . . . . . . . . . . . 32
3.3.2 SETATTR: Set file attributes . . . . . . . . . . . . . . 33
3.3.3 LOOKUP: Lookup filename . . . . . . . . . . . . . . . . 37
3.3.4 ACCESS: Check access permission . . . . . . . . . . . . 40
3.3.5 READLINK: Read from symbolic link . . . . . . . . . . . 44
3.3.6 READ: Read from file . . . . . . . . . . . . . . . . . . 46
3.3.7 WRITE: Write to file . . . . . . . . . . . . . . . . . . 49
3.3.8 CREATE: Create a file . . . . . . . . . . . . . . . . . 54
3.3.9 MKDIR: Create a directory . . . . . . . . . . . . . . . 58
3.3.10 SYMLINK: Create a symbolic link . . . . . . . . . . . . 61
3.3.11 MKNOD: Create a special device . . . . . . . . . . . . . 63
3.3.12 REMOVE: Remove a file . . . . . . . . . . . . . . . . . 67
3.3.13 RMDIR: Remove a directory . . . . . . . . . . . . . . . 69
3.3.14 RENAME: Rename a file or directory . . . . . . . . . . . 71
3.3.15 LINK: Create link to an object . . . . . . . . . . . . . 74
3.3.16 READDIR: Read From directory . . . . . . . . . . . . . . 76
3.3.17 READDIRPLUS: Extended read from directory . . . . . . . 80
3.3.18 FSSTAT: Get dynamic file system information . . . . . . 84
3.3.19 FSINFO: Get static file system information . . . . . . . 86
3.3.20 PATHCONF: Retrieve POSIX information . . . . . . . . . . 90
3.3.21 COMMIT: Commit cached data on a server to stable storage 92
4. Implementation issues . . . . . . . . . . . . . . . . . . 96
4.1 Multiple version support . . . . . . . . . . . . . . . . 96
4.2 Server/client relationship . . . . . . . . . . . . . . . 96
4.3 Path name interpretation . . . . . . . . . . . . . . . . 97
4.4 Permission issues . . . . . . . . . . . . . . . . . . . 98
4.5 Duplicate request cache . . . . . . . . . . . . . . . . 99
4.6 File name component handling . . . . . . . . . . . . . . 101
4.7 Synchronous modifying operations . . . . . . . . . . . . 101
4.8 Stable storage . . . . . . . . . . . . . . . . . . . . . 101
4.9 Lookups and name resolution . . . . . . . . . . . . . . 102
4.10 Adaptive retransmission . . . . . . . . . . . . . . . . 102
4.11 Caching policies . . . . . . . . . . . . . . . . . . . . 102
4.12 Stable versus unstable writes. . . . . . . . . . . . . . 103
4.13 32 bit clients/servers and 64 bit clients/servers. . . . 104
5. Appendix I: Mount protocol . . . . . . . . . . . . . . . . 106
5.1 RPC Information . . . . . . . . . . . . . . . . . . . . 106
5.1.1 Authentication . . . . . . . . . . . . . . . . . . . . 106
5.1.2 Constants . . . . . . . . . . . . . . . . . . . . . . 106
5.1.3 Transport address . . . . . . . . . . . . . . . . . . 106
5.1.4 Sizes . . . . . . . . . . . . . . . . . . . . . . . . 106
5.1.5 Basic Data Types . . . . . . . . . . . . . . . . . . . 106
5.2 Server Procedures . . . . . . . . . . . . . . . . . . . 107
5.2.0 NULL: Do nothing . . . . . . . . . . . . . . . . . . . 108
5.2.1 MNT: Add mount entry . . . . . . . . . . . . . . . . . 109
5.2.2 DUMP: Return mount entries . . . . . . . . . . . . . . 110
5.2.3 UMNT: Remove mount entry . . . . . . . . . . . . . . . 111
5.2.4 UMNTALL: Remove all mount entries . . . . . . . . . . 112
5.2.5 EXPORT: Return export list . . . . . . . . . . . . . . 113
6. Appendix II: Lock manager protocol . . . . . . . . . . . . 114
6.1 RPC Information . . . . . . . . . . . . . . . . . . . . 114
6.1.1 Authentication . . . . . . . . . . . . . . . . . . . . 114
6.1.2 Constants . . . . . . . . . . . . . . . . . . . . . . 114
6.1.3 Transport Address . . . . . . . . . . . . . . . . . . 115
6.1.4 Basic Data Types . . . . . . . . . . . . . . . . . . . 115
6.2 NLM Procedures . . . . . . . . . . . . . . . . . . . . . 118
6.2.0 NULL: Do nothing . . . . . . . . . . . . . . . . . . . 120
6.3 Implementation issues . . . . . . . . . . . . . . . . . 120
6.3.1 64-bit offsets and lengths . . . . . . . . . . . . . . 120
6.3.2 File handles . . . . . . . . . . . . . . . . . . . . . 120
7. Appendix III: Bibliography . . . . . . . . . . . . . . . . 122
8. Security Considerations . . . . . . . . . . . . . . . . . 125
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . 125
10. Authors' Addresses . . . . . . . . . . . . . . . . . . . . 126
1. Introduction
SunのNFSプロトコルは、ネットワークを介して共有ファイルシステムへの
透過的なリモートアクセスを提供します。
NFSプロトコルは、マシン、オペレーティングシステム、ネットワークアーキテクチャ、およびトランスポートプロトコルに依存しないように設計されています。
この独立性は、リモートプロシージャコール（RPC）外部データ表現（XDR）の上に構築されたプリミティブの使用によって達成されています。
NFSバージョン2プロトコルの実装では、パーソナルコンピュータからスーパーコンピュータまで、
様々なマシンに存在します。
NFSプロトコルの初期バージョンはネットワークファイルシステムプロトコル仕様[RFC1094]で
指定されています。
初期の実装の説明は、[Sandberg]で見つけることができます。
サポートする、MOUNTプロトコルは、クライアントがローカルファイルシステム内のポイントへの
リモートディレクトリツリーをアタッチできるよう
オペレーティング·システム固有の機能を実行します。
マウントプロセスは、サーバがエクスポート制御を介してクライアントの制限されたセットへの
リモートアクセス権限を付与することができます。
NFS環境で使用するロック·マネージャは、ファイルのロックをサポートしています。
ネットワークロックマネージャ（NLM）プロトコルは、
別のプロトコルにファイルロックの本質的にステートフルな側面を分離します。
上記のプロトコルとその実装の完全な記述は[X/OpenNFS]で閲覧可能です。
このドキュメントの目的は、次のとおりです。
・NFSバージョン3プロトコルを示す。
・意図された実装を、注釈や説明を介してプロトコルのセマンティクスを説明する。
・MOUNT version3プロトコルを示す。
・NLM version3プロトコルとNLM version4プロトコル間の変更点を簡単に説明する。
標準のテキストは、RPCの手順と引数と結果は、オーバーザワイヤープロトコルを定義し、
これらの手順の意味の説明です。インプリメンテーションの実践を記述する材料は、
プロトコル仕様の理解を助けると考えられるいくつかの実装上の問題と解決策について説明します。
それはすべての実装を記述することはできませんと、
NFSバージョン3プロトコルのUNIXオペレーティング·システムのインプリメンテーションは、
最も頻繁に例を提供するために使用されます。
ことを考えると、実装の議論はオーバーザワイヤープロトコル自体の記述の
権威を負うものではありません。
1.1 Scope of the NFS version 3 protocol
このリビジョンのNFSプロトコルは、新しい要件に対応しています。
大きなファイルやファイルシステムをサポートする必要性は、
64ビットのファイルサイズとオフセットを可能にする拡張機能を求めている。
リビジョンは、サーバー上で実行するアクセスチェックのサポートを追加することにより、
セキュリティが強化されます。パフォーマンスの変更は、3つのタイプがあります。
1.ファイル操作の特定のセットの過線パケットの数は、
このように変更された属性を取得するコールの数を減少し、
すべての操作でファイルの属性を返すことによって低減されます。
2. NFSv2プロトコルの書き込みの同期定義が原因で
書き込みスループットのボトルネックは、
NFSサーバが危険な書き込みを行うことができるようにサポートを追加することで解決されました。
危険な操作が戻る前に安定したストレージにコミットされていないどの書き込みされているが
書き込まれます。この仕様はこれらの危険は、信頼性の高い方法で安定したストレージへの
書き込みをコミットするためのメソッドを定義します。
3。転送サイズに関する制限が緩和されました。
RPCのプロトコルの複数のバージョンをサポートする機能は、
NFSバージョン3プロトコルの実装者は、
NFSバージョン2プロトコルの既存のインストールベースを使用して
クライアントとの後方互換性を提供するサーバーを定義実装することができます。
拡張機能は、既存のNFSプロトコルと[Sandberg]が持続するで説明され、
NFSプロトコルの設計上の特徴のほとんどの進化を表してここで説明する。
この改正により導入された変更の詳細な概要については、
11ページのNFSバージョン2プロトコルからの変更点を参照してください。
1.2 Useful terms
In this specification, a "server" is a machine that provides
resources to the network; a "client" is a machine that accesses
resources over the network; a "user" is a person logged in on a
client; an "application" is a program that executes on a client.
1.3 Remote Procedure Call
SunRPCの仕様は、リモートサービスへのプロシージャ指向のインタフェースを提供します。
各サーバーは、一連の手順でプログラムを提供しています。
NFSサービスは、そのようなプログラムです。ホストアドレスの組み合わせは、
プログラム番号、バージョン番号、プロシージャ番号が
1つのリモート·サービス·プロシージャを指定します。
サーバーは、異なるプロトコルのバージョン番号を使用して、プログラムの複数のバージョンをサポートすることができます。
NFSプロトコルは、それが潜在的に多くの基本的なトランスポートプロトコルに
使用することができるので、その下のレベルから信頼性の任意の特定の
レベルを必要としないように設計されています。
NFSサービスは、下位レベルのネットワークとトランスポート·プロトコル上に
抽象化を提供するRPCに基づいています。
このドキュメントの残りの部分は、NFS環境は[RFC1057]で指定されている
Sun RPCの上に実装されていると仮定しています。完全な議論は[Corbin]で見つけられます。
1.4 External Data Representation
外部データ表現（XDR）仕様は、ネットワーク上のデータ型のセットを表すための
標準的な方法を提供します。これは、異なる、通信しているマシン上で異なるバイトオーダー、
構造アライメント、およびデータ型の表現の問題を解決します。
このドキュメントでは、RPCデータ記述言語は、
NFSサーバーが提供するRPCサービスのプロシージャのそれぞれに
XDR形式のパラメータと結果を指定するために使用されています。
RPCデータ記述言語は、Cプログラミング言語の宣言に似ています。
いくつかの新しい構文が追加されました。
The notation:
string name[SIZE];
string data<DSIZE>;
バイトをDSIZEまでの可変サイズのブロックであるsizeバイトの固定サイズのブロックである名前、
およびデータは、定義されています。この表記は、
最大の固定最大の要素の数が可変固定長配列と配列を示しています。
指定されていないサイズの可変長の定義は、フィールドの最大サイズが存在しないことを意味します。
The discriminated union definition:
union example switch (enum status) {
case OK:
struct {
filename file1;
filename file2;
integer count;
}
case ERROR:
struct {
errstat error;
integer errno;
}
default:
void;
}
ネットワークを介してまず最初に、ステータスと呼ばれる列挙型である構造体を定義します。
状態の値がOKであれば、ネットワークの次のものは、file1、file2を含む構造体である、
とカウントされます。ステータスの値がERRORの場合は、他に、
ネットワーク上の次のものがエラーとerrnoを含む構造になります。
状態の値がOKでもERRORのどちらである場合は、構造中にそれ以上データがない。
XDR型、ハイパーは、8バイト（64ビット）の量である。これは、整数型と同じ方法で使用されています。たとえば、次のように
hyper foo;
unsigned hyper bar;
barは8バイトの符号なしの値ですがfooは、8バイトの符号付きの値です。
RPC / XDRコンパイラは、RPCデータ記述言語入力から、
クライアントとサーバーのスタブを生成するために存在しますが、
NFSの実装では、その使用を必要としません。
XDRによって定義されたデータの標準的なネットワークのために同等の符号化と復号化を
提供する任意のソフトウェアは他のNFSの実装と相互運用するために使用することができます。
XDRは、[RFC1014]で説明されます。
1.5 Authentication and Permission Checking
RPCプロトコルは、呼び出しのたびに認証パラメータ用のスロットが含まれています。
認証パラメータの内容は、サーバーとクライアントによって使用される
uthenticationのタイプによって決定されます。
サーバーは、一度認証にはいくつかの異なった属性をサポートすることができます。
AUTH_NONE属性は、認証情報が渡されない場合はnull認証を提供します。
AUTH_UNIX属性はUNIX形式のユーザーID、グループID、およびそれぞれの呼び出しでグループが用意されています。
AUTH_DES属性は、公開鍵方式を介して交換されたセッションキーを使用して
ネットワーク全体の名前に基づくDES-暗号化された認証パラメータを提供します。
AUTH_KERB属性はケルベロス秘密鍵を介して交換されたセッションキーを使用して
ネットワーク全体の名前に基づいてDES暗号化された認証パラメータを提供します。
NFSサーバーは、それぞれのリモート要求でRPC認証情報から資格を取ることによって
アクセス権をチェックします。たとえば、認証のAUTH_UNIX属性を使用して、
サーバーが呼び出しのたびにユーザの実効ユーザID、実効グループIDとグループを取得し、
アクセスを確認するためにそれらを使用しています。ユーザーIDとグループIDを使用すると、
クライアントとサーバが同じIDリストを共有したり、ローカルユーザーとグループIDの
マッピングを行うのどちらかことを意味します。サーバーとクライアントは、
これらの一貫したユーザIDを実装していないサイトやグループIDのスペースのために、
ユーザからuidに、グループからGIDへのマッピングに同意する必要があります。
実際には、そのようなマッピングは、通常、静的マッピングの方式や、
マウント時にクライアントからユーザによって確立されたマッピングに従って、サーバーで実行されます。
認証のAUTH_DESとAUTH_KERBスタイルはネットワーク全体の名前に基づいています。
それはAUTH_DESの場合には、DES暗号化鍵と公開鍵を使用してセキュリティを強化を提供し、
AUTH_KERBケースでDES暗号化とKerberos秘密鍵（およびチケット）。
再び、サーバとクライアントは、ネットワーク上の特定の名前のIDに同意しなければなりませんが、
アイデンティティへのマッピング名がAUTH_UNIXでuidとgidのマッピングがより独立した
複数のオペレーティングシステムです。認証パラメータが暗号化されているため、
また、悪意のあるユーザーが別のユーザーのネットワークパスワードまたは
そのユーザーのふりをする秘密鍵を知っている必要があります。
同様に、サーバがサーバのふりをすると、ネットワークパスワードを知る必要がありますように
また、暗号化されている検証を返します。
NULL手順は、通常は認証を必要としません。
1.6 Philosophy
この仕様は、クライアントがサーバーにアクセスすることによって
オーバーザワイヤープロトコルであるNFSバージョン3プロトコルを定義します。
プロトコルは、サーバーのファイル·リソースへの、明確に定義されたインタフェースを提供します。
クライアントまたはサーバーがプロトコルを実装し、
NFSバージョン3プロトコルで定義されているものにローカルファイルシステムの
セマンティクスとアクションのマッピングを提供します。
実装では、与えられた環境では、NFSバージョン3プロトコルで定義されているすべての操作と
セマンティクスをサポートできる程度に応じて、様々な程度に異なる場合があります。
実装が存在し、NFSバージョン3プロトコルのさまざまな側面を説明するために使用されていますが、
プロトコルの仕様自体は、クライアントがサーバーのリソースにアクセスする方法の最終的な説明です。
NFSバージョン3プロトコルがオペレーティングシステムに依存しないように設計されているので、
それは必ずしも既存のシステムのセマンティクスと一致しません。
サーバ実装は、プロトコルを支援する最善の努力を行なうことが期待されています。
サーバが特定のプロトコル手順をサポートすることができない場合は、
操作がサポートされていないことを示すエラー、NFS3ERR_NOTSUPを返す可能性があります。
たとえば、多くのオペレーティングシステムはハードリンクの概念をサポートしていません。
ハードリンクをサポートすることができないサーバはLINK要求に応答してNFS3ERR_NOTSUPを返す必要があります。
FSINFOは、プロパティのビットマップで最も一般的にサポートされていない手順を説明します。
また、サーバーはネイティブ特定の操作をサポートしていないかもしれませんが、
優れた機能を提供するために、NFSバージョン3プロトコル実装でそれをエミュレートすることができます。
いくつかのケースでは、サーバはほとんどのセマンティクスをサポートしますが、全てではありません。
たとえば、fattr構造のctimeのフィールドはファイルの属性が最後に変更された時刻を示します。
多くのシステムでは、この情報を保持しません。このケースでは、
GETATTR操作をサポートしていないのではなく、サーバはctimeの代わりに最後に更新された時刻を返すことによって、
それをシミュレートすることができます。
クライアント上の可能性のある副作用のために属性情報をシミュレートするとき、
サーバは慎重でなければなりません。たとえば、多くのクライアントは、
キャッシュの一貫性スキームのための基礎として、ファイルの修正時刻を使用しています。。
NFSサーバは愚かであり、NFSクライアントはスマートです。
それはアプリケーションやユーザーにとって有用であるファイルへのアクセスメソッドに
サーバーが提供する一般的なファイルアクセスを変換するために必要な作業を行うクライアントです。
上記のLINKの例では、サーバーからNFS3ERR_NOTSUPエラーを受信し、
UNIXクライアントは、リンク要求が成功したかの合理的なエラーを返したような、
アプリケーションに見えるようにするために必要な回復を行うだろう。
一般的に、それは回復するクライアントの負担です。
NFSバージョン3プロトコルはステートレスなサーバの実装を前提としています。
ステートレスサーバが正しく機能するためには、そのクライアントの
いずれかに関する状態を維持する必要がないことを意味します。
ステートレスサーバがクラッシュしたときにステートフル·サーバ上の明確な利点を持っています。
ステートレスサーバーで、クライアントは、サーバーが応答するまでだけ要求を再試行する必要があります。
クライアントは、サーバがクラッシュしたことを知る必要はありません。
99ページの重複要求キャッシュの追加のコメントを参照してください。
サーバーが有用であるためには、不揮発性の状態を保持します：ファイルシステムに格納されているデータを。
変更されたデータのフラッシュについてはNFSバージョン3プロトコルの設計上の前提条件、
安定したストレージにデータの損失が発生する可能性のある故障モードの数を減らすことができます。
この方法では、NFSバージョン3プロトコルの実装は、ネットワークの一時的な障害を含む一時的な障害を耐えることができます。
一般的には、NFSバージョン3プロトコルのサーバ実装は安定貯蔵自体の非一時的な障害に耐えることができません。
しかし、このような問題に対処しようとしたフォールトトレラントの実装が存在する。
これはNFSバージョン3プロトコルサーバは重要でない状態を維持できないということではありません。
多くの場合、サーバは、パフォーマンスを向上させるために、以前の操作に関する状態（キャッシュ）を維持します。
たとえば、クライアント要求が、クライアントはシーケンシャルリードを行っていると、
次のクライアント要求がサーバーのデータ·キャッシュから満たされるお読みになることを見越して、
サーバーのデータ·キャッシュへのファイルの次のブロックの先読みの引き金となるかもしれない、
READの代わりに、ディスクから。サーバ上の先読みクライアントの要求でサーバのディスクI / Oをオーバーラップすることにより、
パフォーマンスを向上させます。ここで重要な点は、先読みブロックは正しいサーバ動作の必要がないことです。
サーバがクラッシュして読み取られたバッファのメモリキャッシュを失った場合、
回復は再起動時に簡単です - クライアントはサーバーのディスクからデータを取得する読み取り操作を続行します。
NFSプロトコルのほとんどのデータ変更は、同期操作です。
そのデータはクライアントへの手順に戻りを変更するとき、つまり、クライアントは、
操作が完了し、要求に関連付けられたすべての変更されたデータが安定したストレージ上にあることを仮定することができます。
後者の情報は、通常、メタデータと呼ばれている - たとえば、同期クライアントの書き込み要求はデータ·ブロック、
ファイルシステム情報ブロック、およびファイル属性情報を更新するために、
サーバーを引き起こす可能性があります。 WRITE操作が完了すると、クライアントは、
書き込みデータが安全であることを想定し、それを破棄することができます。
これは、サーバのステートレスな性質の非常に重要な部分です。
サーバがクライアントに返す前に、安定したストレージにダーティ·データをフラッシュしなかった場合、
クライアントは変更されたデータを破棄しても安全だったかを知る方法はありません。
プロシージャを変更する以下のデータが同期しています：WRITE（FILE_SYNCに設定された安定したフラグを持つ）、
CREATE、MKDIR、SYMLINK、MKNOD、REMOVE、RMDIR、RENAME、LINK、およびコミットします。
NFSバージョン3プロトコルでは、WRITEプロシージャがCOMMIT手順と組み合わせて使用される場合、
安全な非同期は、サーバー上の書き込みを紹介しています。
COMMIT手順は、クライアントが安定したストレージにサーバー上で以前の非同期書き込み要求から
データをフラッシュすると、データを再送する必要があるかどうかを検出する方法を提供します。
49ページのWRITEの手順の説明を参照してください（92ページ）コミットします。
LOOKUP手順は、多成分のファイル名（パス名）を横断するためにクライアントによって使用されています。
検索するための各コールは、パスの1つのセグメントを解決するために使用されています。
単一のセグメントにLOOKUPを制限する理由は二つあります：それは階層的なファイル名と、
クライアントとサーバーがファイル·システムへのパス名の異なるマッピングがあるかもしれませんするための共通フォーマットを標準化することは困難です。
これは、いずれかのクライアントがファイル·システム·アタッチメント·ポイントでパス名を突破しなければならない、
またはサーバがクライアントのファイルシステムの接続点について知っている必要があることを含意するでしょう。
NFSバージョン3プロトコル実装では、階層を構築するためにマウントを使用して階層的なファイル名のスペースを構築するクライアントです。
このようなオートマウンタとしてサポートユーティリティ、まだクライアントのマウントプロセスによって駆動されている間に
ファイルの名前空間の共有、一貫したイメージを管理する方法を提供しています。
クライアントは、様々な方法でキャッシュを行うことができます。
NFSバージョン2プロトコルを用いる一般的な方法は、
時間ベースのクライアント·サーバ·キャッシュの一貫性メカニズムを実装することであった。
それは、NFSバージョン3プロトコル実装が同様のメカニズムを使用すると予想されます。
NFSバージョン3プロトコルでは、明示的な属性チェックを排除するために追加の属性情報の形で、
いくつかの明示的なサポートを持っています。しかし、キャッシュが必要でなく、
プロトコルで定義された任意のキャッシュポリシーではありませんされています。
どちらも、NFSバージョン2プロトコルもNFSバージョン3プロトコルは、
厳密なクライアント·サーバの一貫性（と、暗に、クライアントのキャッシュ一貫性）を維持するための手段を提供していません。
1.7 Changes from the NFS Version 2 Protocol
ROOTとWRITECACHE手順が削除されました。MKNOD手順は、CREATEのオーバーロードを排除する
特殊ファイルの作成を可能にするために定義されています。
クライアント上のキャッシュが定義されても、NFSバージョン3プロトコルによって決まりますが、
追加情報とヒントは、より効果的にキャッシュを管理するために
キャッシュを実装するクライアントを許可するためのプロトコルに追加されましたされていません。
操作が属性キャッシュの検証に使用され、後続のGETATTRを最適化するために完了した後、
ファイルまたはディレクトリの属性に影響を与えるの手順は、新しい属性を返すことができます。
さらに、ターゲット·オブジェクトが存在するディレクトリを変更する操作は、
古いものと新しい属性を返すクライアントは、よりインテリジェントなキャッシュを
無効にする手順を実装できるようにするディレクトリ。
ACCESSのプロシージャがサーバー上でチェックするアクセス許可を提供し、
FSSTATプロシージャは、ファイルシステムに関する動的な情報を返しますが、
FSINFO手順はファイルシステムとサーバに関するスタティック情報を返し、
READDIRPLUS手順はディレクトリエントリに加えて、ファイルハンドルと属性を返し、
PATHCONF手順は、ファイルに関するPOSIXのpathconf情報を返します。
以下のNFSバージョン2プロトコルとNFSバージョン3プロトコルの間に重要な変更のリストです。
File handle size
The file handle has been increased to a variable-length array of 64 bytes maximum from a fixed array of 32
bytes. This addresses some known requirements for a slightly larger file handle size. The file handle was
converted from fixed length to variable length to reduce local storage and network bandwidth requirements
for systems which do not utilize the full 64 bytes of length.
Maximum data sizes
The maximum size of a data transfer used in the READ and WRITE procedures is now set by values in the FSINFO
return structure. In addition, preferred transfer sizes are returned by FSINFO. The protocol does not place any
artificial limits on the maximum transfer sizes.
Filenames and pathnames are now specified as strings of variable length. The actual length restrictions are
determined by the client and server implementations as appropriate. The protocol does not place any
artificial limits on the length. The error, NFS3ERR_NAMETOOLONG, is provided to allow the server to
return an indication to the client that it received a pathname that was too long for it to handle.
Error return
Error returns in some instances now return data (for example, attributes). nfsstat3 now defines the full set
of errors that can be returned by a server. No other values are allowed.
File type
The file type now includes NF3CHR and NF3BLK for special files. Attributes for these types include
subfields for UNIX major and minor devices numbers. NF3SOCK and NF3FIFO are now defined for sockets and
fifos in the file system.
File attributes
The blocksize (the size in bytes of a block in the file) field has been removed. The mode field no longer
contains file type information. The size and fileid fields have been widened to eight-byte unsigned
integers from four-byte integers. Major and minor device information is now presented in a distinct
structure. The blocks field name has been changed to used and now contains the total number of bytes used by
the file. It is also an eight-byte unsigned integer.
Set file attributes
In the NFS version 2 protocol, the settable attributes were represented by a subset of the file attributes
structure; the client indicated those attributes which were not to be modified by setting the corresponding
field to -1, overloading some unsigned fields. The set file attributes structure now uses a discriminated
union for each field to tell whether or how to set that field. The atime and mtime fields can be set to either
the server's current time or a time supplied by the client.
LOOKUP
The LOOKUP return structure now includes the attributes for the directory searched.
ACCESS
An ACCESS procedure has been added to allow an explicit over-the-wire permissions check. This addresses known
problems with the superuser ID mapping feature in many server implementations (where, due to mapping of root
user, unexpected permission denied errors could occur while reading from or writing to a file). This also
removes the assumption which was made in the NFS version 2 protocol that access to files was based
solely on UNIX style mode bits.
READ
The reply structure includes a Boolean that is TRUE if the end-of-file was encountered during the READ. This
allows the client to correctly detect end-of-file.
WRITE
The beginoffset and totalcount fields were removed from the WRITE arguments. The reply now includes a count so
that the server can write less than the requested amount of data, if required. An indicator was added to
the arguments to instruct the server as to the level of cache synchronization that is required by the client.
CREATE
An exclusive flag and a create verifier was added for
the exclusive creation of regular files.
MKNOD
This procedure was added to support the creation of
special files. This avoids overloading fields of CREATE
as was done in some NFS version 2 protocol
implementations.
READDIR
The READDIR arguments now include a verifier to allow
the server to validate the cookie. The cookie is now a
64 bit unsigned integer instead of the 4 byte array
which was used in the NFS version 2 protocol. This
will help to reduce interoperability problems.
READDIRPLUS
This procedure was added to return file handles and
attributes in an extended directory list.
FSINFO
FSINFO was added to provide nonvolatile information
about a file system. The reply includes preferred and
maximum read transfer size, preferred and maximum write
transfer size, and flags stating whether links or
symbolic links are supported. Also returned are
preferred transfer size for READDIR procedure replies,
server time granularity, and whether times can be set
in a SETATTR request.
FSSTAT
FSSTAT was added to provide volatile information about
a file system, for use by utilities such as the Unix
system df command. The reply includes the total size
and free space in the file system specified in bytes,
the total number of files and number of free file slots
in the file system, and an estimate of time between
file system modifications (for use in cache consistency
checking algorithms).
COMMIT
The COMMIT procedure provides the synchronization
mechanism to be used with asynchronous WRITE
operations.
2. RPC Information
2.1 Authentication
The NFS service uses AUTH_NONE in the NULL procedure. AUTH_UNIX, AUTH_DES, or AUTH_KERB are used for all other procedures. Other authentication types may be supported in the future.
2.2 Constants
These are the RPC constants needed to call the NFS Version 3 service. They are given in decimal.
PROGRAM 100003
VERSION 3
2.3 Transport address
The NFS protocol is normally supported over the TCP and UDP protocols. It uses port 2049, the same as the NFS version 2 protocol.
2.4 Sizes
These are the sizes, given in decimal bytes, of various XDR structures used in the NFS version 3 protocol:
NFS3_FHSIZE 64
The maximum size in bytes of the opaque file handle.
NFS3_COOKIEVERFSIZE 8
The size in bytes of the opaque cookie verifier passed by READDIR and READDIRPLUS.
NFS3_CREATEVERFSIZE 8
The size in bytes of the opaque verifier used for exclusive CREATE.
NFS3_WRITEVERFSIZE 8
The size in bytes of the opaque verifier used for asynchronous WRITE.
2.5 Basic Data Types
The following XDR definitions are basic definitions that are used in other structures.
uint64
typedef unsigned hyper uint64;
int64
typedef hyper int64;
uint32
typedef unsigned long uint32;
int32
typedef long int32;
filename3
typedef string filename3<>;
nfspath3
typedef string nfspath3<>;
fileid3
typedef uint64 fileid3;
cookie3
typedef uint64 cookie3;
cookieverf3
typedef opaque cookieverf3[NFS3_COOKIEVERFSIZE];
createverf3
typedef opaque createverf3[NFS3_CREATEVERFSIZE];
writeverf3
typedef opaque writeverf3[NFS3_WRITEVERFSIZE];
uid3
typedef uint32 uid3;
gid3
typedef uint32 gid3;
size3
typedef uint64 size3;
offset3
typedef uint64 offset3;
mode3
typedef uint32 mode3;
count3
typedef uint32 count3;
nfsstat3
enum nfsstat3 {
NFS3_OK = 0,
NFS3ERR_PERM = 1,
NFS3ERR_NOENT = 2,
NFS3ERR_IO = 5,
NFS3ERR_NXIO = 6,
NFS3ERR_ACCES = 13,
NFS3ERR_EXIST = 17,
NFS3ERR_XDEV = 18,
NFS3ERR_NODEV = 19,
NFS3ERR_NOTDIR = 20,
NFS3ERR_ISDIR = 21,
NFS3ERR_INVAL = 22,
NFS3ERR_FBIG = 27,
NFS3ERR_NOSPC = 28,
NFS3ERR_ROFS = 30,
NFS3ERR_MLINK = 31,
NFS3ERR_NAMETOOLONG = 63,
NFS3ERR_NOTEMPTY = 66,
NFS3ERR_DQUOT = 69,
NFS3ERR_STALE = 70,
NFS3ERR_REMOTE = 71,
NFS3ERR_BADHANDLE = 10001,
NFS3ERR_NOT_SYNC = 10002,
NFS3ERR_BAD_COOKIE = 10003,
NFS3ERR_NOTSUPP = 10004,
NFS3ERR_TOOSMALL = 10005,
NFS3ERR_SERVERFAULT = 10006,
NFS3ERR_BADTYPE = 10007,
NFS3ERR_JUKEBOX = 10008
};
The nfsstat3 type is returned with every procedure's results except for the NULL procedure. A value of NFS3_OK indicates that
the call completed successfully. Any other value indicates that some error occurred on the call, as identified by the error
code. Note that the precise numeric encoding must be followed.
No other values may be returned by a server. Servers are expected to make a best effort mapping of error conditions to
the set of error codes defined. In addition, no error precedences are specified by this specification. Error
precedences determine the error value that should be returned when more than one error applies in a given situation. The error
precedence will be determined by the individual server implementation. If the client requires specific error
precedences, it should check for the specific errors for itself.
2.6 Defined Error Numbers
A description of each defined error follows:
NFS3_OK
Indicates the call completed successfully.
NFS3ERR_PERM
Not owner. The operation was not allowed because the caller is either not a privileged user (root) or not the owner of the target of the operation.
NFS3ERR_NOENT
No such file or directory. The file or directory name specified does not exist.
NFS3ERR_IO
I/O error. A hard error (for example, a disk error) occurred while processing the requested operation.
NFS3ERR_NXIO
I/O error. No such device or address.
NFS3ERR_ACCES
Permission denied. The caller does not have the correct permission to perform the requested operation. Contrast this with NFS3ERR_PERM, which restricts itself to owner or privileged user permission failures.
NFS3ERR_EXIST
File exists. The file specified already exists.
NFS3ERR_XDEV
Attempt to do a cross-device hard link.
NFS3ERR_NODEV
No such device.
NFS3ERR_NOTDIR
Not a directory. The caller specified a non-directory in a directory operation.
NFS3ERR_ISDIR
Is a directory. The caller specified a directory in a non-directory operation.
NFS3ERR_INVAL
Invalid argument or unsupported argument for an operation. Two examples are attempting a READLINK on an object other than a symbolic link or attempting to
SETATTR a time field on a server that does not support this operation.
NFS3ERR_FBIG
File too large. The operation would have caused a file to grow beyond the server's limit.
NFS3ERR_NOSPC
No space left on device. The operation would have caused the server's file system to exceed its limit.
NFS3ERR_ROFS
Read-only file system. A modifying operation was attempted on a read-only file system.
NFS3ERR_MLINK
Too many hard links.
NFS3ERR_NAMETOOLONG
The filename in an operation was too long.
NFS3ERR_NOTEMPTY
An attempt was made to remove a directory that was not
empty.
NFS3ERR_DQUOT
Resource (quota) hard limit exceeded. The user's resource limit on the server has been exceeded.
NFS3ERR_STALE
Invalid file handle. The file handle given in the arguments was invalid.
The file referred to by that file handle no longer exists or access to it has been revoked.
NFS3ERR_REMOTE
Too many levels of remote in path. The file handle given in the arguments referred to a file on a non-local file system on the server.
NFS3ERR_BADHANDLE
Illegal NFS file handle. The file handle failed internal consistency checks.
NFS3ERR_NOT_SYNC
Update synchronization mismatch was detected during a SETATTR operation.
NFS3ERR_BAD_COOKIE
READDIR or READDIRPLUS cookie is stale.
NFS3ERR_NOTSUPP
Operation is not supported.
NFS3ERR_TOOSMALL
Buffer or request is too small.
NFS3ERR_SERVERFAULT
An error occurred on the server which does not map to any of the legal NFS version 3 protocol error values.
The client should translate this into an appropriate error. UNIX clients may choose to translate this to EIO.
NFS3ERR_BADTYPE
An attempt was made to create an object of a type not supported by the server.
NFS3ERR_JUKEBOX
The server initiated the request, but was not able to complete it in a timely fashion.
The client should wait and then try the request with a new RPC transaction ID.
For example, this error should be returned from a server that supports hierarchical storage and receives a request to process a file that has been migrated.
In this case, the server should start the immigration process and respond to client with this error.
ftype3
enum ftype3 {
NF3REG = 1,
NF3DIR = 2,
NF3BLK = 3,
NF3CHR = 4,
NF3LNK = 5,
NF3SOCK = 6,
NF3FIFO = 7
};
The enumeration, ftype3, gives the type of a file. The type, NF3REG, is a regular file, NF3DIR is a directory,
NF3BLK is a block special device file, NF3CHR is a character special device file, NF3LNK is a symbolic link,
NF3SOCK is a socket, and NF3FIFO is a named pipe. Note that the precise enum encoding must be followed.
specdata3
struct specdata3 {
uint32 specdata1;
uint32 specdata2;
};
The interpretation of the two words depends on the type of file system object.
For a block special (NF3BLK) or character special (NF3CHR) file, specdata1 and specdata2 are the major and minor device numbers, respectively.
(This is obviously a UNIX-specific interpretation.) For all other file types,
these two elements should either be set to 0 or the values should be agreed upon by the client and server.
If the client and server do not agree upon the values, the client should treat these fields as if they are set to 0.
This data field is returned as part of the fattr3 structure and so is available from all replies returning attributes.
Since these fields are otherwise unused for objects which are not devices, out of band information can be passed from the server to the client.
However, once again, both the server and the client must agree on the values passed.
nfs_fh3
struct nfs_fh3 {
opaque data<NFS3_FHSIZE>;
};
The nfs_fh3 is the variable-length opaque object returned by the server on LOOKUP, CREATE, SYMLINK, MKNOD, LINK, or READDIRPLUS operations,
which is used by the client on subsequent operations to reference the file.
The file handle contains all the information the server needs to distinguish an individual file.
To the client, the file handle is opaque. The client stores file handles for use in a later request and can compare two file handles
from the same server for equality by doing a byte-by-byte comparison, but cannot otherwise interpret the contents of file handles.
If two file handles from the same server are equal, they must refer to the same file, but if they are not equal,
no conclusions can be drawn. Servers should try to maintain a one-to-one correspondence between file handles and files,
but this is not required. Clients should use file handle comparisons only to improve performance, not for correct behavior.
Servers can revoke the access provided by a file handle at any time.
If the file handle passed in a call refers to a file system object that no longer exists on the server or access for that file handle has been revoked,
the error, NFS3ERR_STALE, should be returned.
nfstime3
struct nfstime3 {
uint32 seconds;
uint32 nseconds;
};
The nfstime3 structure gives the number of seconds and nanoseconds since midnight January 1, 1970 Greenwich Mean Time.
It is used to pass time and date information.
The times associated with files are all server times except in the case of a SETATTR operation where the client can explicitly set the file time.
A server converts to and from local time when processing time values, preserving as much accuracy as possible.
If the precision of timestamps stored for a file is less than that
defined by NFS version 3 protocol, loss of precision can occur.
An adjunct time maintenance protocol is recommended to reduce client and server time skew.
fattr3
struct fattr3 {
ftype3 type;
mode3 mode;
uint32 nlink;
uid3 uid;
gid3 gid;
size3 size;
size3 used;
specdata3 rdev;
uint64 fsid;
fileid3 fileid;
nfstime3 atime;
nfstime3 mtime;
nfstime3 ctime;
};
This structure defines the attributes of a file system object.
It is returned by most operations on an object; in the case of operations that affect two objects (for example, a MKDIR that modifies the target directory attributes and defines new attributes for the newly created directory), the attributes for both may be returned. In some cases, the attributes are returned in the structure, wcc_data, which is defined below; in other cases the attributes are returned alone. The main changes from the NFS version 2 protocol are that many of the fields have been widened and the major/minor device information is now presented in a distinct structure rather than being packed into a word.
The fattr3 structure contains the basic attributes of a file.
All servers should support this set of attributes even if they have to simulate some of the fields. Type is the type of the file. Mode is the protection mode bits. Nlink is the number of hard links to the file - that is, the number of different names for the same file. Uid is the user ID of the owner of the file.
Gid is the group ID of the group of the file. Size is the size of the file in bytes. Used is the number of bytes of disk space that the file actually uses (which can be smaller than the size because the file may have holes or it may be larger due to fragmentation). Rdev describes the device file if the file type is NF3CHR or NF3BLK - see specdata3 on page 20. Fsid is the file system identifier for the file system. Fileid is a number which uniquely identifies the file within its file system (on UNIX
this would be the inumber). Atime is the time when the file data was last accessed. Mtime is the time when the file data was last modified. Ctime is the time when the attributes of the file were last changed. Writing to the file changes the ctime in addition to the mtime.
The mode bits are defined as follows:
0x00800 Set user ID on execution.
0x00400 Set group ID on execution.
0x00200 Save swapped text (not defined in POSIX).
0x00100 Read permission for owner.
0x00080 Write permission for owner.
0x00040 Execute permission for owner on a file. Or lookup
(search) permission for owner in directory.
0x00020 Read permission for group.
0x00010 Write permission for group.
0x00008 Execute permission for group on a file. Or lookup
(search) permission for group in directory.
0x00004 Read permission for others.
0x00002 Write permission for others.
0x00001 Execute permission for others on a file. Or lookup
(search) permission for others in directory.
post_op_attr
union post_op_attr switch (bool attributes_follow) {
case TRUE:
fattr3 attributes;
case FALSE:
void;
};
This structure is used for returning attributes in those operations that are not directly involved with manipulating attributes. One of the principles of this revision of the NFS protocol is to return the real value from the indicated operation and not an error from an incidental operation.
The post_op_attr structure was designed to allow the server to recover from errors encountered while getting attributes.
This appears to make returning attributes optional. However, server implementors are strongly encouraged to make best effort to return attributes whenever possible, even when returning an error.
wcc_attr
struct wcc_attr {
size3 size;
nfstime3 mtime;
nfstime3 ctime;
};
This is the subset of pre-operation attributes needed to better support the weak cache consistency semantics. Size is the file size in bytes of the object before the operation. Mtime is the time of last modification of the object before the operation.
Ctime is the time of last change to the attributes of the object before the operation. See discussion in wcc_attr on page 24.
The use of mtime by clients to detect changes to file system objects residing on a server is dependent on the granularity of the time base on the server.
pre_op_attr
union pre_op_attr switch (bool attributes_follow) {
case TRUE:
wcc_attr attributes;
case FALSE:
void;
};
wcc_data
struct wcc_data {
pre_op_attr before;
post_op_attr after;
};
When a client performs an operation that modifies the state of a file or directory on the server, it cannot immediately determine from the post-operation attributes whether the operation just performed was the only operation on the object since the last time the client received the attributes for the object. This is important, since if an intervening operation has changed the object, the client will need to invalidate any cached data for the object (except for the data that it just wrote).
To deal with this, the notion of weak cache consistency data or wcc_data is introduced. A wcc_data structure consists of certain key fields from the object attributes before the operation, together with the object attributes after the operation. This
information allows the client to manage its cache more accurately than in NFS version 2 protocol implementations. The term, weak cache consistency, emphasizes the fact that this mechanism does not provide the strict server-client consistency that a cache consistency protocol would provide.
In order to support the weak cache consistency model, the server will need to be able to get the pre-operation attributes of the object, perform the intended modify operation, and then get the post-operation attributes atomically. If there is a window for the object to get modified between the operation and either of the get attributes operations, then the client will not be able to determine whether it was the only entity to modify the object. Some information will have been lost, thus weakening the weak cache consistency guarantees.
post_op_fh3
union post_op_fh3 switch (bool handle_follows) {
case TRUE:
nfs_fh3 handle;
case FALSE:
void;
};
One of the principles of this revision of the NFS protocol is to return the real value from the indicated operation and not an error from an incidental operation. The post_op_fh3 structure was designed to allow the server to recover from errors encountered while constructing a file handle.
This is the structure used to return a file handle from the CREATE, MKDIR, SYMLINK, MKNOD, and READDIRPLUS requests. In each case, the client can get the file handle by issuing a LOOKUP request after a successful return from one of the listed operations. Returning the file handle is an optimization so that the client is not forced to immediately issue a LOOKUP request to get the file handle.
sattr3
enum time_how {
DONT_CHANGE = 0,
SET_TO_SERVER_TIME = 1,
SET_TO_CLIENT_TIME = 2
};
union set_mode3 switch (bool set_it) {
case TRUE:
mode3 mode;
default:
void;
};
union set_uid3 switch (bool set_it) {
case TRUE:
uid3 uid;
default:
void;
};
union set_gid3 switch (bool set_it) {
case TRUE:
gid3 gid;
default:
void;
};
union set_size3 switch (bool set_it) {
case TRUE:
size3 size;
default:
void;
};
union set_atime switch (time_how set_it) {
case SET_TO_CLIENT_TIME:
nfstime3 atime;
default:
void;
};
union set_mtime switch (time_how set_it) {
case SET_TO_CLIENT_TIME:
nfstime3 mtime;
default:
void;
};
struct sattr3 {
set_mode3 mode;
set_uid3 uid;
set_gid3 gid;
set_size3 size;
set_atime atime;
set_mtime mtime;
};
The sattr3 structure contains the file attributes that can be set from the client. The fields are the same as the similarly named fields in the fattr3 structure. In the NFS version 3 protocol, the settable attributes are described by a structure containing a set of discriminated unions. Each union indicates whether the corresponding attribute is to be updated, and if so, how.
There are two forms of discriminated unions used. In setting the mode, uid, gid, or size, the discriminated union is switched on a boolean, set_it; if it is TRUE, a value of the appropriate type is then encoded.
In setting the atime or mtime, the union is switched on an enumeration type, set_it. If set_it has the value DONT_CHANGE, the corresponding attribute is unchanged. If it has the value, SET_TO_SERVER_TIME, the corresponding attribute is set by the server to its local time; no data is provided by the client.
Finally, if set_it has the value, SET_TO_CLIENT_TIME, the attribute is set to the time passed by the client in an nfstime3 structure. (See FSINFO on page 86, which addresses the issue of time granularity).
diropargs3
struct diropargs3 {
nfs_fh3 dir;
filename3 name;
};
The diropargs3 structure is used in directory operations. The file handle, dir, identifies the directory in which to manipulate or access the file, name. See additional comments in File name component handling on page 101.
3. Server Procedures
The following sections define the RPC procedures that are supplied by an NFS version 3 protocol server. The RPC procedure number is given at the top of the page with the
name. The SYNOPSIS provides the name of the procedure, the list of the names of the arguments, the list of the names of the results, followed by the XDR argument declarations and results declarations. The information in the SYNOPSIS is specified in RPC Data Description Language as defined in [RFC1014]. The DESCRIPTION section tells what the procedure
is expected to do and how its arguments and results are used. The ERRORS section lists the errors returned for specific types of failures. These lists are not intended to be the definitive statement of all of the errors which can be returned by any specific procedure, but as a guide for the more common errors which may be returned. Client
implementations should be prepared to deal with unexpected errors coming from a server. The IMPLEMENTATION field gives information about how the procedure is expected to work and how it should be used by clients.
program NFS_PROGRAM {
version NFS_V3 {
void
NFSPROC3_NULL(void) = 0;
GETATTR3res
NFSPROC3_GETATTR(GETATTR3args) = 1;
SETATTR3res
NFSPROC3_SETATTR(SETATTR3args) = 2;
LOOKUP3res
NFSPROC3_LOOKUP(LOOKUP3args) = 3;
ACCESS3res
NFSPROC3_ACCESS(ACCESS3args) = 4;
READLINK3res
NFSPROC3_READLINK(READLINK3args) = 5;
READ3res
NFSPROC3_READ(READ3args) = 6;
WRITE3res
NFSPROC3_WRITE(WRITE3args) = 7;
CREATE3res
NFSPROC3_CREATE(CREATE3args) = 8;
MKDIR3res
NFSPROC3_MKDIR(MKDIR3args) = 9;
SYMLINK3res
NFSPROC3_SYMLINK(SYMLINK3args) = 10;
MKNOD3res
NFSPROC3_MKNOD(MKNOD3args) = 11;
REMOVE3res
NFSPROC3_REMOVE(REMOVE3args) = 12;
RMDIR3res
NFSPROC3_RMDIR(RMDIR3args) = 13;
RENAME3res
NFSPROC3_RENAME(RENAME3args) = 14;
LINK3res
NFSPROC3_LINK(LINK3args) = 15;
READDIR3res
NFSPROC3_READDIR(READDIR3args) = 16;
READDIRPLUS3res
NFSPROC3_READDIRPLUS(READDIRPLUS3args) = 17;
FSSTAT3res
NFSPROC3_FSSTAT(FSSTAT3args) = 18;
FSINFO3res
NFSPROC3_FSINFO(FSINFO3args) = 19;
PATHCONF3res
NFSPROC3_PATHCONF(PATHCONF3args) = 20;
COMMIT3res
NFSPROC3_COMMIT(COMMIT3args) = 21;
} = 3;
} = 100003;
Out of range (undefined) procedure numbers result in RPC
errors. Refer to [RFC1057] for more detail.
3.1 General comments on attributes and consistency data on failure
For those procedures that return either post_op_attr or wcc_data structures on failure, the discriminated union may contain the
pre-operation attributes of the object or object parent directory. This depends on the error encountered and may also
depend on the particular server implementation. Implementors are strongly encouraged to return as much attribute data as possible
upon failure, but client implementors need to be aware that their implementation must correctly handle the variant return
instance where no attributes or consistency data is returned.
3.2 General comments on filenames
The following comments apply to all NFS version 3 protocol procedures in which the client provides one or more filenames in
the arguments: LOOKUP, CREATE, MKDIR, SYMLINK, MKNOD, REMOVE, RMDIR, RENAME, and LINK.
1. The filename must not be null nor may it be the null
string. The server should return the error, NFS3ERR_ACCES, if
it receives such a filename. On some clients, the filename, ``''
or a null string, is assumed to be an alias for the current
directory. Clients which require this functionality should
implement it for themselves and not depend upon the server to
support such semantics.
2. A filename having the value of "." is assumed to be an
alias for the current directory. Clients which require this
functionality should implement it for themselves and not depend
upon the server to support such semantics. However, the server
should be able to handle such a filename correctly.
3. A filename having the value of ".." is assumed to be an
alias for the parent of the current directory, i.e. the
directory which contains the current directory. The server
should be prepared to handle this semantic, if it supports
directories, even if those directories do not contain UNIX-style
"." or ".." entries.
4. If the filename is longer than the maximum for the file
system (see PATHCONF on page 90, specifically name_max), the
result depends on the value of the PATHCONF flag, no_trunc. If
no_trunc is FALSE, the filename will be silently truncated to
name_max bytes. If no_trunc is TRUE and the filename exceeds the
server's file system maximum filename length, the operation will
fail with the error, NFS3ERR_NAMETOOLONG.
5. In general, there will be characters that a server will
not be able to handle as part of a filename. This set of
characters will vary from server to server and from
implementation to implementation. In most cases, it is the
server which will control the client's view of the file system.
If the server receives a filename containing characters that it
can not handle, the error, NFS3ERR_EACCES, should be returned.
Client implementations should be prepared to handle this side
affect of heterogeneity.
See also comments in File name component handling on page 101.
3.3.0 Procedure 0: NULL - Do nothing
SYNOPSIS
void NFSPROC3_NULL(void) = 0;
DESCRIPTION
Procedure NULL does not do any work. It is made available to
allow server response testing and timing.
IMPLEMENTATION
It is important that this procedure do no work at all so
that it can be used to measure the overhead of processing
a service request. By convention, the NULL procedure
should never require any authentication. A server may
choose to ignore this convention, in a more secure
implementation, where responding to the NULL procedure
call acknowledges the existence of a resource to an
unauthenticated client.
ERRORS
Since the NULL procedure takes no NFS version 3 protocol
arguments and returns no NFS version 3 protocol response,
it can not return an NFS version 3 protocol error.
However, it is possible that some server implementations
may return RPC errors based on security and authentication
requirements.
3.3.1 Procedure 1: GETATTR - Get file attributes
SYNOPSIS
GETATTR3res NFSPROC3_GETATTR(GETATTR3args) = 1;
struct GETATTR3args {
nfs_fh3 object;
};
struct GETATTR3resok {
fattr3 obj_attributes;
};
union GETATTR3res switch (nfsstat3 status) {
case NFS3_OK:
GETATTR3resok resok;
default:
void;
};
DESCRIPTION
Procedure GETATTR retrieves the attributes for a specified
file system object. The object is identified by the file
handle that the server returned as part of the response
from a LOOKUP, CREATE, MKDIR, SYMLINK, MKNOD, or
READDIRPLUS procedure (or from the MOUNT service,
described elsewhere). On entry, the arguments in
GETATTR3args are:
object
The file handle of an object whose attributes are to be
retrieved.
On successful return, GETATTR3res.status is NFS3_OK and
GETATTR3res.resok contains:
obj_attributes
The attributes for the object.
Otherwise, GETATTR3res.status contains the error on failure and
no other results are returned.
IMPLEMENTATION
The attributes of file system objects is a point of major
disagreement between different operating systems. Servers
should make a best attempt to support all of the
attributes in the fattr3 structure so that clients can
count on this as a common ground. Some mapping may be
required to map local attributes to those in the fattr3
structure.
Today, most client NFS version 3 protocol implementations
implement a time-bounded attribute caching scheme to
reduce over-the-wire attribute checks.
ERRORS
NFS3ERR_IO
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_SERVERFAULT
SEE ALSO
ACCESS.
3.3.2 Procedure 2: SETATTR - Set file attributes
SYNOPSIS
SETATTR3res NFSPROC3_SETATTR(SETATTR3args) = 2;
union sattrguard3 switch (bool check) {
case TRUE:
nfstime3 obj_ctime;
case FALSE:
void;
};
struct SETATTR3args {
nfs_fh3 object;
sattr3 new_attributes;
sattrguard3 guard;
};
struct SETATTR3resok {
wcc_data obj_wcc;
};
struct SETATTR3resfail {
wcc_data obj_wcc;
};
union SETATTR3res switch (nfsstat3 status) {
case NFS3_OK:
SETATTR3resok resok;
default:
SETATTR3resfail resfail;
};
DESCRIPTION
Procedure SETATTR changes one or more of the attributes of
a file system object on the server. The new attributes are
specified by a sattr3 structure. On entry, the arguments
in SETATTR3args are:
object
The file handle for the object.
new_attributes
A sattr3 structure containing booleans and
enumerations describing the attributes to be set and the new
values for those attributes.
guard
A sattrguard3 union:
check
TRUE if the server is to verify that guard.obj_ctime
matches the ctime for the object; FALSE otherwise.
A client may request that the server check that the object
is in an expected state before performing the SETATTR
operation. To do this, it sets the argument guard.check to
TRUE and the client passes a time value in guard.obj_ctime.
If guard.check is TRUE, the server must compare the value of
guard.obj_ctime to the current ctime of the object. If the
values are different, the server must preserve the object
attributes and must return a status of NFS3ERR_NOT_SYNC.
If guard.check is FALSE, the server will not perform this
check.
On successful return, SETATTR3res.status is NFS3_OK and
SETATTR3res.resok contains:
obj_wcc
A wcc_data structure containing the old and new
attributes for the object.
Otherwise, SETATTR3res.status contains the error on
failure and SETATTR3res.resfail contains the following:
obj_wcc
A wcc_data structure containing the old and new
attributes for the object.
IMPLEMENTATION
The guard.check mechanism allows the client to avoid
changing the attributes of an object on the basis of stale
attributes. It does not guarantee exactly-once semantics.
In particular, if a reply is lost and the server does not
detect the retransmission of the request, the procedure
can fail with the error, NFS3ERR_NOT_SYNC, even though the
attribute setting was previously performed successfully.
The client can attempt to recover from this error by
getting fresh attributes from the server and sending a new
SETATTR request using the new ctime. The client can
optionally check the attributes to avoid the second
SETATTR request if the new attributes show that the
attributes have already been set as desired (though it may
not have been the issuing client that set the
attributes).
The new_attributes.size field is used to request changes
to the size of a file. A value of 0 causes the file to be
truncated, a value less than the current size of the file
causes data from new size to the end of the file to be
discarded, and a size greater than the current size of the
file causes logically zeroed data bytes to be added to the
end of the file. Servers are free to implement this using
holes or actual zero data bytes. Clients should not make
any assumptions regarding a server's implementation of
this feature, beyond that the bytes returned will be
zeroed. Servers must support extending the file size via
SETATTR.
SETATTR is not guaranteed atomic. A failed SETATTR may
partially change a file's attributes.
Changing the size of a file with SETATTR indirectly
changes the mtime. A client must account for this as size
changes can result in data deletion.
If server and client times differ, programs that compare
client time to file times can break. A time maintenance
protocol should be used to limit client/server time skew.
In a heterogeneous environment, it is quite possible that
the server will not be able to support the full range of
SETATTR requests. The error, NFS3ERR_INVAL, may be
returned if the server can not store a uid or gid in its
own representation of uids or gids, respectively. If the
server can only support 32 bit offsets and sizes, a
SETATTR request to set the size of a file to larger than
can be represented in 32 bits will be rejected with this
same error.
ERRORS
NFS3ERR_PERM
NFS3ERR_IO
NFS3ERR_ACCES
NFS3ERR_INVAL
NFS3ERR_NOSPC
NFS3ERR_ROFS
NFS3ERR_DQUOT
NFS3ERR_NOT_SYNC
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_SERVERFAULT
SEE ALSO
CREATE, MKDIR, SYMLINK, and MKNOD.
3.3.3 Procedure 3: LOOKUP - Lookup filename
SYNOPSIS
LOOKUP3res NFSPROC3_LOOKUP(LOOKUP3args) = 3;
struct LOOKUP3args {
diropargs3 what;
};
struct LOOKUP3resok {
nfs_fh3 object;
post_op_attr obj_attributes;
post_op_attr dir_attributes;
};
struct LOOKUP3resfail {
post_op_attr dir_attributes;
};
union LOOKUP3res switch (nfsstat3 status) {
case NFS3_OK:
LOOKUP3resok resok;
default:
LOOKUP3resfail resfail;
};
DESCRIPTION
Procedure LOOKUP searches a directory for a specific name
and returns the file handle for the corresponding file
system object. On entry, the arguments in LOOKUP3args
are:
what
Object to look up:
dir
The file handle for the directory to search.
name
The filename to be searched for. Refer to General
comments on filenames on page 30.
On successful return, LOOKUP3res.status is NFS3_OK and
LOOKUP3res.resok contains:
object
The file handle of the object corresponding to
what.name.
obj_attributes
The attributes of the object corresponding to
what.name.
dir_attributes
The post-operation attributes of the directory,
what.dir.
Otherwise, LOOKUP3res.status contains the error on failure and
LOOKUP3res.resfail contains the following:
dir_attributes
The post-operation attributes for the directory,
what.dir.
IMPLEMENTATION
At first glance, in the case where what.name refers to a
mount point on the server, two different replies seem
possible. The server can return either the file handle for
the underlying directory that is mounted on or the file
handle of the root of the mounted directory. This
ambiguity is simply resolved. A server will not allow a
LOOKUP operation to cross a mountpoint to the root of a
different filesystem, even if the filesystem is exported.
This does not prevent a client from accessing a hierarchy
of filesystems exported by a server, but the client must
mount each of the filesystems individually so that the
mountpoint crossing takes place on the client. A given
server implementation may refine these rules given
capabilities or limitations particular to that
implementation. Refer to [X/OpenNFS] for a discussion on
exporting file systems.
Two filenames are distinguished, as in the NFS version 2
protocol. The name, ".", is an alias for the current
directory and the name, "..", is an alias for the parent
directory; that is, the directory that includes the
specified directory as a member. There is no facility for
dealing with a multiparented directory and the NFS
protocol assumes a hierarchical organization, organized as
a single-rooted tree.
Note that this procedure does not follow symbolic links.
The client is responsible for all parsing of filenames
including filenames that are modified by symbolic links
encountered during the lookup process.
ERRORS
NFS3ERR_IO
NFS3ERR_NOENT
NFS3ERR_ACCES
NFS3ERR_NOTDIR
NFS3ERR_NAMETOOLONG
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_SERVERFAULT
SEE ALSO
CREATE, MKDIR, SYMLINK, MKNOD, READDIRPLUS, and PATHCONF.
3.3.4 Procedure 4: ACCESS - Check Access Permission
SYNOPSIS
ACCESS3res NFSPROC3_ACCESS(ACCESS3args) = 4;
const ACCESS3_READ = 0x0001;
const ACCESS3_LOOKUP = 0x0002;
const ACCESS3_MODIFY = 0x0004;
const ACCESS3_EXTEND = 0x0008;
const ACCESS3_DELETE = 0x0010;
const ACCESS3_EXECUTE = 0x0020;
struct ACCESS3args {
nfs_fh3 object;
uint32 access;
};
struct ACCESS3resok {
post_op_attr obj_attributes;
uint32 access;
};
struct ACCESS3resfail {
post_op_attr obj_attributes;
};
union ACCESS3res switch (nfsstat3 status) {
case NFS3_OK:
ACCESS3resok resok;
default:
ACCESS3resfail resfail;
};
DESCRIPTION
Procedure ACCESS determines the access rights that a user,
as identified by the credentials in the request, has with
respect to a file system object. The client encodes the
set of permissions that are to be checked in a bit mask.
The server checks the permissions encoded in the bit mask.
A status of NFS3_OK is returned along with a bit mask
encoded with the permissions that the client is allowed.
The results of this procedure are necessarily advisory in
nature. That is, a return status of NFS3_OK and the
appropriate bit set in the bit mask does not imply that
such access will be allowed to the file system object in
the future, as access rights can be revoked by the server
at any time.
On entry, the arguments in ACCESS3args are:
object
The file handle for the file system object to which
access is to be checked.
access
A bit mask of access permissions to check.
The following access permissions may be requested:
ACCESS3_READ
Read data from file or read a directory.
ACCESS3_LOOKUP
Look up a name in a directory (no meaning for
non-directory objects).
ACCESS3_MODIFY
Rewrite existing file data or modify existing
directory entries.
ACCESS3_EXTEND
Write new data or add directory entries.
ACCESS3_DELETE
Delete an existing directory entry.
ACCESS3_EXECUTE
Execute file (no meaning for a directory).
On successful return, ACCESS3res.status is NFS3_OK. The
server should return a status of NFS3_OK if no errors
occurred that prevented the server from making the
required access checks. The results in ACCESS3res.resok
are:
obj_attributes
The post-operation attributes of object.
access
A bit mask of access permissions indicating access
rights for the authentication credentials provided with
the request.
Otherwise, ACCESS3res.status contains the error on failure
and ACCESS3res.resfail contains the following:
obj_attributes
The attributes of object - if access to attributes is
permitted.
IMPLEMENTATION
In general, it is not sufficient for the client to attempt
to deduce access permissions by inspecting the uid, gid,
and mode fields in the file attributes, since the server
may perform uid or gid mapping or enforce additional
access control restrictions. It is also possible that the
NFS version 3 protocol server may not be in the same ID
space as the NFS version 3 protocol client. In these cases
(and perhaps others), the NFS version 3 protocol client
can not reliably perform an access check with only current
file attributes.
In the NFS version 2 protocol, the only reliable way to
determine whether an operation was allowed was to try it
and see if it succeeded or failed. Using the ACCESS
procedure in the NFS version 3 protocol, the client can
ask the server to indicate whether or not one or more
classes of operations are permitted. The ACCESS operation
is provided to allow clients to check before doing a
series of operations. This is useful in operating systems
(such as UNIX) where permission checking is done only when
a file or directory is opened. This procedure is also
invoked by NFS client access procedure (called possibly
through access(2)). The intent is to make the behavior of
opening a remote file more consistent with the behavior of
opening a local file.
The information returned by the server in response to an
ACCESS call is not permanent. It was correct at the exact
time that the server performed the checks, but not
necessarily afterwards. The server can revoke access
permission at any time.
The NFS version 3 protocol client should use the effective
credentials of the user to build the authentication
information in the ACCESS request used to determine access
rights. It is the effective user and group credentials
that are used in subsequent read and write operations. See
the comments in Permission issues on page 98 for more
information on this topic.
Many implementations do not directly support the
ACCESS3_DELETE permission. Operating systems like UNIX
will ignore the ACCESS3_DELETE bit if set on an access
request on a non-directory object. In these systems,
delete permission on a file is determined by the access
permissions on the directory in which the file resides,
instead of being determined by the permissions of the file
itself. Thus, the bit mask returned for such a request
will have the ACCESS3_DELETE bit set to 0, indicating that
the client does not have this permission.
ERRORS
NFS3ERR_IO
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_SERVERFAULT
SEE ALSO
GETATTR.
3.3.5 Procedure 5: READLINK - Read from symbolic link
SYNOPSIS
READLINK3res NFSPROC3_READLINK(READLINK3args) = 5;
struct READLINK3args {
nfs_fh3 symlink;
};
struct READLINK3resok {
post_op_attr symlink_attributes;
nfspath3 data;
};
struct READLINK3resfail {
post_op_attr symlink_attributes;
};
union READLINK3res switch (nfsstat3 status) {
case NFS3_OK:
READLINK3resok resok;
default:
READLINK3resfail resfail;
};
DESCRIPTION
Procedure READLINK reads the data associated with a
symbolic link. The data is an ASCII string that is opaque
to the server. That is, whether created by the NFS
version 3 protocol software from a client or created
locally on the server, the data in a symbolic link is not
interpreted when created, but is simply stored. On entry,
the arguments in READLINK3args are:
symlink
The file handle for a symbolic link (file system object
of type NF3LNK).
On successful return, READLINK3res.status is NFS3_OK and
READLINK3res.resok contains:
data
The data associated with the symbolic link.
symlink_attributes
The post-operation attributes for the symbolic link.
Otherwise, READLINK3res.status contains the error on
failure and READLINK3res.resfail contains the following:
symlink_attributes
The post-operation attributes for the symbolic link.
IMPLEMENTATION
A symbolic link is nominally a pointer to another file.
The data is not necessarily interpreted by the server,
just stored in the file. It is possible for a client
implementation to store a path name that is not meaningful
to the server operating system in a symbolic link. A
READLINK operation returns the data to the client for
interpretation. If different implementations want to share
access to symbolic links, then they must agree on the
interpretation of the data in the symbolic link.
The READLINK operation is only allowed on objects of type,
NF3LNK. The server should return the error,
NFS3ERR_INVAL, if the object is not of type, NF3LNK.
(Note: The X/Open XNFS Specification for the NFS version 2
protocol defined the error status in this case as
NFSERR_NXIO. This is inconsistent with existing server
practice.)
ERRORS
NFS3ERR_IO
NFS3ERR_INVAL
NFS3ERR_ACCES
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_NOTSUPP
NFS3ERR_SERVERFAULT
SEE ALSO
READLINK, SYMLINK.
3.3.6 Procedure 6: READ - ファイルから読み込み
SYNOPSIS
READ3res NFSPROC3_READ(READ3args) = 6;
struct READ3args {
nfs_fh3 file;
offset3 offset;
count3 count;
};
struct READ3resok {
post_op_attr file_attributes;
count3 count;
bool eof;
opaque data<>;
};
struct READ3resfail {
post_op_attr file_attributes;
};
union READ3res switch (nfsstat3 status) {
case NFS3_OK:
READ3resok resok;
default:
READ3resfail resfail;
};
DESCRIPTION
Procedure READ reads data from a file. On entry, the arguments in READ3args are:
file
The file handle of the file from which data is to be read. This must identify a file system object of type, NF3REG.
offset
The position within the file at which the read is to begin. An offset of 0 means to read data starting at
the beginning of the file. If offset is greater than or equal to the size of the file, the status, NFS3_OK, is
returned with count set to 0 and eof set to TRUE, subject to access permissions checking.
count
The number of bytes of data that are to be read. If count is 0, the READ will succeed and return 0 bytes of
data, subject to access permissions checking. count must be less than or equal to the value of the rtmax
field in the FSINFO reply structure for the file system that contains file. If greater, the server may return
only rtmax bytes, resulting in a short read.
On successful return, READ3res.status is NFS3_OK and READ3res.resok contains:
file_attributes
The attributes of the file on completion of the read.
count
The number of bytes of data returned by the read.
eof
If the read ended at the end-of-file (formally, in a correctly formed READ request, if READ3args.offset plus
READ3resok.count is equal to the size of the file), eof is returned as TRUE; otherwise it is FALSE. A
successful READ of an empty file will always return eof as TRUE.
data
The counted data read from the file.
Otherwise, READ3res.status contains the error on failure and READ3res.resfail contains the following:
file_attributes
The post-operation attributes of the file.
IMPLEMENTATION
NFSバージョンでREADとWRITE操作に使用されるnfsdataタイプは、
要求または応答のデータ部分を定義する2プロトコルは、可変長の不透明なバイト配列に変更されました。
プロトコルによって許容される最大サイズは現在、XDRと基本的な輸送が許容するものによって制限されています。
NFSv3プロトコルによって課されたどんな人工の限界はありません。詳細については、FSINFO手順の説明を参照してください。
サーバはデータのcountバイト未満を返すことが可能です。サーバがFALSEに要求されたカウントとEOFセット未満を返した場合、クライアントは、発行する必要があります。
もう一つは残りのデータを取得するためにお読みください。サーバは、いくつかの状況下で要求されたより少ないデータを返す可能性があります。
ファイルが要求しているクライアントがケースであると信じているからファイルサイズを変更し、
サーバ自体におそらく別のクライアントまたはによって切り捨てられている可能性があります。
これは、クライアントが利用可能な実際のデータ量を減らすことができます。
それは、サーバが転送サイズをオフにバックアップし、読み出し要求リターンを減少させる可能性があります。
サーバ·リソースの枯渇も小さく、読み取りの戻り値を必要とする可能性があります。
いくつかのNFSバージョン2プロトコルクライアント実装は、EOFを示すように、短いリードの応答を解釈することにしました。
NFSv3プロトコルのEOFフラグの追加は、EOFを処理する正しい方法を提供します。
ファイル·システム·オブジェクト·タイプは、通常のファイルではありませんでした場合、
いくつかのNFSバージョン2プロトコルサーバ実装が間違ってNFSERR_ISDIRを返しました。
NFSバージョン3プロトコルの正しい戻り値はNFS3ERR_INVALです。
ERRORS
NFS3ERR_IO
NFS3ERR_NXIO
NFS3ERR_ACCES
NFS3ERR_INVAL
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_SERVERFAULT
SEE ALSO
READLINK.
3.3.7 Procedure 7: WRITE - Write to file
SYNOPSIS
WRITE3res NFSPROC3_WRITE(WRITE3args) = 7;
enum stable_how {
UNSTABLE = 0,
DATA_SYNC = 1,
FILE_SYNC = 2
};
struct WRITE3args {
nfs_fh3 file;
offset3 offset;
count3 count;
stable_how stable;
opaque data<>;
};
struct WRITE3resok {
wcc_data file_wcc;
count3 count;
stable_how committed;
writeverf3 verf;
};
struct WRITE3resfail {
wcc_data file_wcc;
};
union WRITE3res switch (nfsstat3 status) {
case NFS3_OK:
WRITE3resok resok;
default:
WRITE3resfail resfail;
};
DESCRIPTION
Procedure WRITE writes data to a file. On entry, the
arguments in WRITE3args are:
file
The file handle for the file to which data is to be
written. This must identify a file system object of
type, NF3REG.
offset
The position within the file at which the write is to
begin. An offset of 0 means to write data starting at
the beginning of the file.
count
The number of bytes of data to be written. If count is
0, the WRITE will succeed and return a count of 0,
barring errors due to permissions checking. The size of
data must be less than or equal to the value of the
wtmax field in the FSINFO reply structure for the file
system that contains file. If greater, the server may
write only wtmax bytes, resulting in a short write.
stable
If stable is FILE_SYNC, the server must commit the data written plus all file system metadata to stable storage
before returning results. This corresponds to the NFS version 2 protocol semantics. Any other behavior
constitutes a protocol violation. If stable is DATA_SYNC, then the server must commit all of the data
to stable storage and enough of the metadata to retrieve the data before returning. The server
implementor is free to implement DATA_SYNC in the same fashion as FILE_SYNC, but with a possible performance
drop. If stable is UNSTABLE, the server is free to commit any part of the data and the metadata to stable
storage, including all or none, before returning a reply to the client. There is no guarantee whether or
when any uncommitted data will subsequently be committed to stable storage. The only guarantees made
by the server are that it will not destroy any data without changing the value of verf and that it will not
commit the data and metadata at a level less than that requested by the client. See the discussion on COMMIT
on page 92 for more information on if and when data is committed to stable storage.
data
The data to be written to the file.
On successful return, WRITE3res.status is NFS3_OK and
WRITE3res.resok contains:
file_wcc
Weak cache consistency data for the file. For a client
that requires only the post-write file attributes,
these can be found in file_wcc.after.
count
The number of bytes of data written to the file. The
server may write fewer bytes than requested. If so, the
actual number of bytes written starting at location,
offset, is returned.
committed
The server should return an indication of the level of commitment of the data and metadata via committed. If
the server committed all data and metadata to stable storage, committed should be set to FILE_SYNC. If the
level of commitment was at least as strong as DATA_SYNC, then committed should be set to DATA_SYNC.
Otherwise, committed must be returned as UNSTABLE. If stable was FILE_SYNC, then committed must also be
FILE_SYNC: anything else constitutes a protocol violation. If stable was DATA_SYNC, then committed may
be FILE_SYNC or DATA_SYNC: anything else constitutes a protocol violation. If stable was UNSTABLE, then
committed may be either FILE_SYNC, DATA_SYNC, or UNSTABLE.
verf
This is a cookie that the client can use to determine
whether the server has changed state between a call to
WRITE and a subsequent call to either WRITE or COMMIT.
This cookie must be consistent during a single instance
of the NFS version 3 protocol service and must be
unique between instances of the NFS version 3 protocol
server, where uncommitted data may be lost.
Otherwise, WRITE3res.status contains the error on failure
and WRITE3res.resfail contains the following:
file_wcc
Weak cache consistency data for the file. For a client
that requires only the post-write file attributes,
these can be found in file_wcc.after. Even though the
write failed, full wcc_data is returned to allow the
client to determine whether the failed write resulted
in any change to the file.
If a client writes data to the server with the stable
argument set to UNSTABLE and the reply yields a committed
response of DATA_SYNC or UNSTABLE, the client will follow
up some time in the future with a COMMIT operation to
synchronize outstanding asynchronous data and metadata
with the server's stable storage, barring client error. It
is possible that due to client crash or other error that a
subsequent COMMIT will not be received by the server.
IMPLEMENTATION
NFSバージョンでREADとWRITE操作に使用されるnfsdataタイプは、要求または応答のデータ部分を定義する2プロトコルは、
可変長の不透明なバイト配列に変更されました。プロトコルによって許容される最大サイズは現在、
XDRと基本的な輸送が許容するものによって制限されています。
NFSv3プロトコルによって課されたどんな人工の限界はありません。詳細については、FSINFO手順の説明を参照してください。
サーバはデータのcountバイト未満を書き込みすることが可能です。データが全く書かれない限り、このケースでは、
サーバーがエラーを返すべきではありません。サーバはカウントバイト未満を書き込みした場合、
クライアントは残りのデータを書き込むために別のWRITEを発行する必要があります。
これは、ファイルにデータを書き込むという行為は、ファイルのmtimeが更新されるようになりますことを想定しています。
ファイルの内容が変更されない限り、ファイルのmtimeは変更すべきではありません。したがって、0に設定したカウントによるWRITE要求は、
更新するファイルのmtimeを引き起こすべきではありません。
NFSv3プロトコルでは、安全な非同期書き込みが導入されています。 COMMITが続く不安定版（unstable）に安定集合があるWRITEの組み合わせは、
NFSバージョン2プロトコル、同期はすべて安定したストレージへの書き込みはコミットする必要がで見つかった、
パフォーマンスのボトルネックに対処しています。
安定貯蔵の定義は歴史的に競合のポイントされています。安定したストレージは、次の予想されるプロパティは、
実装では、設計上の問題の解決に役立つ可能性があります。安定貯蔵は生き残る永続的なストレージです。
1。繰り返される停電。
2。ハードウェア障害（どんなボード、電源などの）。
3。リブートサイクルを含んでいて繰り返されるソフトウェアのクラッシュ、。
この定義は安定貯蔵モジュール自体の故障には対応していません。
クッキー、VERFは、クライアントはキャッシュされ、コミットされていないデータが失われる可能性があります
その上のNFSバージョン3プロトコルサーバの異なるインスタンスを検出できるように定義されています。
ほとんどのケースでは、verfはクライアントがサーバの再起動を検出することができます。
この情報は、クライアントが安全にサーバがキャッシュされたデータを失っているかどうかを判断できるようにする必要があります。
サーバーが予期せず失敗し、クライアントはそれが安定したストレージにキャッシュされたデータをフラッシュしていない可能性があります
前のWRITE要求（UNSTABLEに設定された安定した引数で、どのにコミット結果が同様にUNSTABLEとして返された行われます）
からのデータをコミットしている場合。回復の負担は、クライアント上にあり、クライアントはサーバにデータを再送する必要があります。
提案されVERFクッキーはサーバが起動された時刻、またはサーバーが最後に起動された時刻を
（もしあれば失われたバッファ内のリブートなしでサーバを再起動する）を使用することになります。
結果にコミットされたフィールドは、クライアントがより効果的なキャッシュを行うことができます。
サーバが安定したストレージへのすべてのWRITE要求をコミットしている場合、それは関係なく、
引数の安定したフィールドの値の、FILE_SYNCへのコミットセットを返す必要があります。
NVRAMアクセラレータを使用するサーバーは、このポリシーを実装するために選択することができます。
クライアントが既にサーバー上でコミットされたキャッシュされたデータを捨てることによってキャッシュの効果を高めるためにこれを使用することができます。
ユーザーのクォータを超過したとき、いくつかの実装がNFS3ERR_NOSPCの代わりにNFS3ERR_DQUOTを返す可能性があります。
ファイル·システム·オブジェクト·タイプは、通常のファイルではありませんでした場合、
いくつかのNFSバージョン2プロトコルサーバ実装が間違ってNFSERR_ISDIRを返しました。
NFSバージョン3プロトコルの正しい戻り値はNFS3ERR_INVALです。
ERRORS
NFS3ERR_IO
NFS3ERR_ACCES
NFS3ERR_FBIG
NFS3ERR_DQUOT
NFS3ERR_NOSPC
NFS3ERR_ROFS
NFS3ERR_INVAL
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_SERVERFAULT
SEE ALSO
COMMIT.
3.3.8 Procedure 8: CREATE - ファイル作成
SYNOPSIS
CREATE3res NFSPROC3_CREATE(CREATE3args) = 8;
enum createmode3 {
UNCHECKED = 0,
GUARDED = 1,
EXCLUSIVE = 2
};
union createhow3 switch (createmode3 mode) {
case UNCHECKED:
case GUARDED:
sattr3 obj_attributes;
case EXCLUSIVE:
createverf3 verf;
};
struct CREATE3args {
diropargs3 where;
createhow3 how;
};
struct CREATE3resok {
post_op_fh3 obj;
post_op_attr obj_attributes;
wcc_data dir_wcc;
};
struct CREATE3resfail {
wcc_data dir_wcc;
};
union CREATE3res switch (nfsstat3 status) {
case NFS3_OK:
CREATE3resok resok;
default:
CREATE3resfail resfail;
};
DESCRIPTION
Procedure CREATE creates a regular file. On entry, the arguments in CREATE3args are:
where
The location of the file to be created:
dir
The file handle for the directory in which the file is to be created.
name
The name that is to be associated with the created file. Refer to General comments on filenames on page 30.
When creating a regular file, there are three ways to create the file as defined by:
how
A discriminated union describing how the server is to
handle the file creation along with the appropriate
attributes:
mode
One of UNCHECKED, GUARDED, and EXCLUSIVE. UNCHECKED means that the file should be created without checking
for the existence of a duplicate file in the same directory. In this case, how.obj_attributes is a sattr3
describing the initial attributes for the file. GUARDED specifies that the server should check for the presence
of a duplicate file before performing the create and should fail the request with NFS3ERR_EXIST if a
duplicate file exists. If the file does not exist, the request is performed as described for UNCHECKED.
EXCLUSIVE specifies that the server is to follow exclusive creation semantics, using the verifier to
ensure exclusive creation of the target. No attributes may be provided in this case, since the server may use
the target file metadata to store the createverf3 verifier.
On successful return, CREATE3res.status is NFS3_OK and the
results in CREATE3res.resok are:
obj
The file handle of the newly created regular file.
obj_attributes
The attributes of the regular file just created.
dir_wcc
Weak cache consistency data for the directory,
where.dir. For a client that requires on the
post-CREATE directory attributes, these can be found in
dir_wcc.after.
Otherwise, CREATE3res.status contains the error on failure
and CREATE3res.resfail contains the following:
dir_wcc
Weak cache consistency data for the directory,
where.dir. For a client that requires only the
post-CREATE directory attributes, these can be found in
dir_wcc.after. Even though the CREATE failed, full
wcc_data is returned to allow the client to determine
whether the failing CREATE resulted in any change to
the directory.
IMPLEMENTATION
最初の属性構造内の特定のフィールドは、通常のファイルに加えて、
デバイスとFIFOの作成を示すためにオーバーロードされたNFSバージョン2プロトコルとは異なり、
この手順は、通常のファイルの作成をサポートしています。 MKNOD手順は、
デバイスとFIFOの作成を処理するNFSバージョン3プロトコルで導入されました。
実装では、過負荷のセマンティクスを作成する方法NFSバージョン3プロトコルには理由があるべきではありません。
NFSバージョン3プロトコルの一つの側面は、特に慎重な検討手順を保証します。
CREATE機構は、通常のファイルの信頼性のある排他的な作成をサポートするために導入されています。
how.modeがexclusiveの場合機構が場に出る。このケースでは、how.verfは、
合理的に一意であることが予想されるベリファイアが含まれています。
クライアント識別子、恐らくクライアントネットワークアドレス、
およびクライアントによって生成される一意の番号の組み合わせは、
おそらくRPCトランザクション識別子は、適切であるかもしれません。
ファイルが存在しない場合、サーバーはファイルを作成し、安定したストレージ内のベリファイアを格納します。
任意のファイルの属性を格納するためのメカニズムを提供していないファイルシステムの場合、
サーバーはベリファイアを格納するファイルのメタデータの1つまたは複数の要素を使用することができます。
検証は、要求の再送信に誤ったエラーを防ぐために、安定したストレージに格納する必要があります。
排他的なセマンティクスはアプリケーションにとって重要であるので、
それは排他的な作成が実行されていることを想定しています。ため予想使用量の、排他的なCREATEは、
ベリファイアを格納するための通常揮発性の重複要求キャッシュだけに頼ることはありません。
揮発性記憶装置内の重複要求キャッシュは、クラッシュを生き延びるないし、
実際に障害のウィンドウを開く、長いネットワークパーティションにフラッシュすることがあります。
UNIXローカルファイルシステム環境では、作成時にベリファイアの期待保管場所は、
ファイルのメタデータ（タイムスタンプ）です。この理由のために、排他的ファイルを作成、
サーバーが検証を保存するためにどこにもないであろうため、初期の属性を含めることはできません。
サーバーは、可能性のため安定したストレージに検証をコミットするための要件
これらの排他的な作成のセマンティクスをサポートできない場合は、
NFS3ERR_NOTSUPP、エラーでCREATE要求を失敗する必要があります。
ファイルが既に存在する場合、排他的なCREATE要求時に、サーバはファイルのベリファイアを再構築し、
要求の検証とそれを比較します。それらが一致すれば、サーバは成功として要求を扱います。
要求は、応答が失われ、サーバーの重複要求キャッシュメカニズムが検出されなかったこととなる以前では、
成功したリクエストの重複であると推定される。検証が一致しない場合、要求はステータス、NFS3ERR_EXISTで拒否されます。
クライアントが成功した排他的な作成を実行した後は、正しいファイル属性を設定するためにSETATTRを発行する必要があります。
それがそうするまで、サーバの実装では、ベリファイアを格納するために過負荷ファイルのメタデータに必要になる場合がありますので、
それは、ファイルの属性のいずれかに頼るべきではありません。
ガード属性の使用は必ず1回のセマンティクスを提供していません。
応答が失われ、サーバはリクエストの再送を検出しない場合、特に、プロシージャは作成が正常に実行されているにもかかわらず、
NFS3ERR_EXISTで失敗することができます。
30ページのファイル名の一般コメントを参照してください。
ERRORS
NFS3ERR_IO
NFS3ERR_ACCES
NFS3ERR_EXIST
NFS3ERR_NOTDIR
NFS3ERR_NOSPC
NFS3ERR_ROFS
NFS3ERR_NAMETOOLONG
NFS3ERR_DQUOT
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_NOTSUPP
NFS3ERR_SERVERFAULT
SEE ALSO
MKDIR, SYMLINK, MKNOD, and PATHCONF.
3.3.9 Procedure 9: MKDIR - Create a directory
SYNOPSIS
MKDIR3res NFSPROC3_MKDIR(MKDIR3args) = 9;
struct MKDIR3args {
diropargs3 where;
sattr3 attributes;
};
struct MKDIR3resok {
post_op_fh3 obj;
post_op_attr obj_attributes;
wcc_data dir_wcc;
};
struct MKDIR3resfail {
wcc_data dir_wcc;
};
union MKDIR3res switch (nfsstat3 status) {
case NFS3_OK:
MKDIR3resok resok;
default:
MKDIR3resfail resfail;
};
DESCRIPTION
Procedure MKDIR creates a new subdirectory. On entry, the
arguments in MKDIR3args are:
where
The location of the subdirectory to be created:
dir
The file handle for the directory in which the
subdirectory is to be created.
name
The name that is to be associated with the created
subdirectory. Refer to General comments on filenames
on page 30.
attributes
The initial attributes for the subdirectory.
On successful return, MKDIR3res.status is NFS3_OK and the
results in MKDIR3res.resok are:
obj
The file handle for the newly created directory.
obj_attributes
The attributes for the newly created subdirectory.
dir_wcc
Weak cache consistency data for the directory,
where.dir. For a client that requires only the
post-MKDIR directory attributes, these can be found in
dir_wcc.after.
Otherwise, MKDIR3res.status contains the error on failure
and MKDIR3res.resfail contains the following:
dir_wcc
Weak cache consistency data for the directory,
where.dir. For a client that requires only the
post-MKDIR directory attributes, these can be found in
dir_wcc.after. Even though the MKDIR failed, full
wcc_data is returned to allow the client to determine
whether the failing MKDIR resulted in any change to the
directory.
IMPLEMENTATION
Many server implementations will not allow the filenames,
"." or "..", to be used as targets in a MKDIR operation.
In this case, the server should return NFS3ERR_EXIST.
Refer to General comments on filenames on page 30.
ERRORS
NFS3ERR_IO
NFS3ERR_ACCES
NFS3ERR_EXIST
NFS3ERR_NOTDIR
NFS3ERR_NOSPC
NFS3ERR_ROFS
NFS3ERR_NAMETOOLONG
NFS3ERR_DQUOT
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_NOTSUPP
NFS3ERR_SERVERFAULT
SEE ALSO
CREATE, SYMLINK, MKNOD, and PATHCONF.
3.3.10 Procedure 10: SYMLINK - Create a symbolic link
SYNOPSIS
SYMLINK3res NFSPROC3_SYMLINK(SYMLINK3args) = 10;
struct symlinkdata3 {
sattr3 symlink_attributes;
nfspath3 symlink_data;
};
struct SYMLINK3args {
diropargs3 where;
symlinkdata3 symlink;
};
struct SYMLINK3resok {
post_op_fh3 obj;
post_op_attr obj_attributes;
wcc_data dir_wcc;
};
struct SYMLINK3resfail {
wcc_data dir_wcc;
};
union SYMLINK3res switch (nfsstat3 status) {
case NFS3_OK:
SYMLINK3resok resok;
default:
SYMLINK3resfail resfail;
};
DESCRIPTION
Procedure SYMLINK creates a new symbolic link. On entry,
the arguments in SYMLINK3args are:
where
The location of the symbolic link to be created:
dir
The file handle for the directory in which the
symbolic link is to be created.
name
The name that is to be associated with the created
symbolic link. Refer to General comments on
filenames on page 30.
symlink
The symbolic link to create:
symlink_attributes
The initial attributes for the symbolic link.
symlink_data
The string containing the symbolic link data.
On successful return, SYMLINK3res.status is NFS3_OK and
SYMLINK3res.resok contains:
obj
The file handle for the newly created symbolic link.
obj_attributes
The attributes for the newly created symbolic link.
dir_wcc
Weak cache consistency data for the directory,
where.dir. For a client that requires only the
post-SYMLINK directory attributes, these can be found
in dir_wcc.after.
Otherwise, SYMLINK3res.status contains the error on
failure and SYMLINK3res.resfail contains the following:
dir_wcc
Weak cache consistency data for the directory,
where.dir. For a client that requires only the
post-SYMLINK directory attributes, these can be found
in dir_wcc.after. Even though the SYMLINK failed, full
wcc_data is returned to allow the client to determine
whether the failing SYMLINK changed the directory.
IMPLEMENTATION
Refer to General comments on filenames on page 30.
For symbolic links, the actual file system node and its
contents are expected to be created in a single atomic
operation. That is, once the symbolic link is visible,
there must not be a window where a READLINK would fail or
return incorrect data.
ERRORS
NFS3ERR_IO
NFS3ERR_ACCES
NFS3ERR_EXIST
NFS3ERR_NOTDIR
NFS3ERR_NOSPC
NFS3ERR_ROFS
NFS3ERR_NAMETOOLONG
NFS3ERR_DQUOT
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_NOTSUPP
NFS3ERR_SERVERFAULT
SEE ALSO
READLINK, CREATE, MKDIR, MKNOD, FSINFO, and PATHCONF.
3.3.11 Procedure 11: MKNOD - Create a special device
SYNOPSIS
MKNOD3res NFSPROC3_MKNOD(MKNOD3args) = 11;
struct devicedata3 {
sattr3 dev_attributes;
specdata3 spec;
};
union mknoddata3 switch (ftype3 type) {
case NF3CHR:
case NF3BLK:
devicedata3 device;
case NF3SOCK:
case NF3FIFO:
sattr3 pipe_attributes;
default:
void;
};
struct MKNOD3args {
diropargs3 where;
mknoddata3 what;
};
struct MKNOD3resok {
post_op_fh3 obj;
post_op_attr obj_attributes;
wcc_data dir_wcc;
};
struct MKNOD3resfail {
wcc_data dir_wcc;
};
union MKNOD3res switch (nfsstat3 status) {
case NFS3_OK:
MKNOD3resok resok;
default:
MKNOD3resfail resfail;
};
DESCRIPTION
Procedure MKNOD creates a new special file of the type,
what.type. Special files can be device files or named
pipes. On entry, the arguments in MKNOD3args are:
where
The location of the special file to be created:
dir
The file handle for the directory in which the
special file is to be created.
name
The name that is to be associated with the created
special file. Refer to General comments on filenames
on page 30.
what
A discriminated union identifying the type of the
special file to be created along with the data and
attributes appropriate to the type of the special
file:
type
The type of the object to be created.
When creating a character special file (what.type is
NF3CHR) or a block special file (what.type is NF3BLK),
what includes:
device
A structure devicedata3 with the following components:
dev_attributes
The initial attributes for the special file.
spec
The major number stored in device.spec.specdata1 and
the minor number stored in device.spec.specdata2.
When creating a socket (what.type is NF3SOCK) or a FIFO
(what.type is NF3FIFO), what includes:
pipe_attributes
The initial attributes for the special file.
On successful return, MKNOD3res.status is NFS3_OK and
MKNOD3res.resok contains:
obj
The file handle for the newly created special file.
obj_attributes
The attributes for the newly created special file.
dir_wcc
Weak cache consistency data for the directory,
where.dir. For a client that requires only the
post-MKNOD directory attributes, these can be found in
dir_wcc.after.
Otherwise, MKNOD3res.status contains the error on failure
and MKNOD3res.resfail contains the following:
dir_wcc
Weak cache consistency data for the directory,
where.dir. For a client that requires only the
post-MKNOD directory attributes, these can be found in
dir_wcc.after. Even though the MKNOD failed, full
wcc_data is returned to allow the client to determine
whether the failing MKNOD changed the directory.
IMPLEMENTATION
Refer to General comments on filenames on page 30.
Without explicit support for special file type creation in
the NFS version 2 protocol, fields in the CREATE arguments
were overloaded to indicate creation of certain types of
objects. This overloading is not necessary in the NFS
version 3 protocol.
If the server does not support any of the defined types,
the error, NFS3ERR_NOTSUPP, should be returned. Otherwise,
if the server does not support the target type or the
target type is illegal, the error, NFS3ERR_BADTYPE, should
be returned. Note that NF3REG, NF3DIR, and NF3LNK are
illegal types for MKNOD. The procedures, CREATE, MKDIR,
and SYMLINK should be used to create these file types,
respectively, instead of MKNOD.
ERRORS
NFS3ERR_IO
NFS3ERR_ACCES
NFS3ERR_EXIST
NFS3ERR_NOTDIR
NFS3ERR_NOSPC
NFS3ERR_ROFS
NFS3ERR_NAMETOOLONG
NFS3ERR_DQUOT
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_NOTSUPP
NFS3ERR_SERVERFAULT
NFS3ERR_BADTYPE
SEE ALSO
CREATE, MKDIR, SYMLINK, and PATHCONF.
3.3.12 Procedure 12: REMOVE - Remove a File
SYNOPSIS
REMOVE3res NFSPROC3_REMOVE(REMOVE3args) = 12;
struct REMOVE3args {
diropargs3 object;
};
struct REMOVE3resok {
wcc_data dir_wcc;
};
struct REMOVE3resfail {
wcc_data dir_wcc;
};
union REMOVE3res switch (nfsstat3 status) {
case NFS3_OK:
REMOVE3resok resok;
default:
REMOVE3resfail resfail;
};
DESCRIPTION
Procedure REMOVE removes (deletes) an entry from a
directory. If the entry in the directory was the last
reference to the corresponding file system object, the
object may be destroyed. On entry, the arguments in
REMOVE3args are:
object
A diropargs3 structure identifying the entry to be
removed:
dir
The file handle for the directory from which the entry
is to be removed.
name
The name of the entry to be removed. Refer to General
comments on filenames on page 30.
On successful return, REMOVE3res.status is NFS3_OK and
REMOVE3res.resok contains:
dir_wcc
Weak cache consistency data for the directory,
object.dir. For a client that requires only the
post-REMOVE directory attributes, these can be found in
dir_wcc.after.
Otherwise, REMOVE3res.status contains the error on failure
and REMOVE3res.resfail contains the following:
dir_wcc
Weak cache consistency data for the directory,
object.dir. For a client that requires only the
post-REMOVE directory attributes, these can be found in
dir_wcc.after. Even though the REMOVE failed, full
wcc_data is returned to allow the client to determine
whether the failing REMOVE changed the directory.
IMPLEMENTATION
In general, REMOVE is intended to remove non-directory
file objects and RMDIR is to be used to remove
directories. However, REMOVE can be used to remove
directories, subject to restrictions imposed by either the
client or server interfaces. This had been a source of
confusion in the NFS version 2 protocol.
The concept of last reference is server specific. However,
if the nlink field in the previous attributes of the
object had the value 1, the client should not rely on
referring to the object via a file handle. Likewise, the
client should not rely on the resources (disk space,
directory entry, and so on.) formerly associated with the
object becoming immediately available. Thus, if a client
needs to be able to continue to access a file after using
REMOVE to remove it, the client should take steps to make
sure that the file will still be accessible. The usual
mechanism used is to use RENAME to rename the file from
its old name to a new hidden name.
Refer to General comments on filenames on page 30.
ERRORS
NFS3ERR_NOENT
NFS3ERR_IO
NFS3ERR_ACCES
NFS3ERR_NOTDIR
NFS3ERR_NAMETOOLONG
NFS3ERR_ROFS
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_SERVERFAULT
SEE ALSO
RMDIR and RENAME.
3.3.13 Procedure 13: RMDIR - Remove a Directory
SYNOPSIS
RMDIR3res NFSPROC3_RMDIR(RMDIR3args) = 13;
struct RMDIR3args {
diropargs3 object;
};
struct RMDIR3resok {
wcc_data dir_wcc;
};
struct RMDIR3resfail {
wcc_data dir_wcc;
};
union RMDIR3res switch (nfsstat3 status) {
case NFS3_OK:
RMDIR3resok resok;
default:
RMDIR3resfail resfail;
};
DESCRIPTION
Procedure RMDIR removes (deletes) a subdirectory from a
directory. If the directory entry of the subdirectory is
the last reference to the subdirectory, the subdirectory
may be destroyed. On entry, the arguments in RMDIR3args
are:
object
A diropargs3 structure identifying the directory entry
to be removed:
dir
The file handle for the directory from which the
subdirectory is to be removed.
name
The name of the subdirectory to be removed. Refer to
General comments on filenames on page 30.
On successful return, RMDIR3res.status is NFS3_OK and
RMDIR3res.resok contains:
dir_wcc
Weak cache consistency data for the directory,
object.dir. For a client that requires only the
post-RMDIR directory attributes, these can be found in
dir_wcc.after.
Otherwise, RMDIR3res.status contains the error on failure
and RMDIR3res.resfail contains the following:
dir_wcc
Weak cache consistency data for the directory,
object.dir. For a client that requires only the
post-RMDIR directory attributes, these can be found in
dir_wcc.after. Note that even though the RMDIR failed,
full wcc_data is returned to allow the client to
determine whether the failing RMDIR changed the
directory.
IMPLEMENTATION
Note that on some servers, removal of a non-empty
directory is disallowed.
On some servers, the filename, ".", is illegal. These
servers will return the error, NFS3ERR_INVAL. On some
servers, the filename, "..", is illegal. These servers
will return the error, NFS3ERR_EXIST. This would seem
inconsistent, but allows these servers to comply with
their own specific interface definitions. Clients should
be prepared to handle both cases.
The client should not rely on the resources (disk space,
directory entry, and so on.) formerly associated with the
directory becoming immediately available.
ERRORS
NFS3ERR_NOENT
NFS3ERR_IO
NFS3ERR_ACCES
NFS3ERR_INVAL
NFS3ERR_EXIST
NFS3ERR_NOTDIR
NFS3ERR_NAMETOOLONG
NFS3ERR_ROFS
NFS3ERR_NOTEMPTY
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_NOTSUPP
NFS3ERR_SERVERFAULT
SEE ALSO
REMOVE.
3.3.14 Procedure 14: RENAME - Rename a File or Directory
SYNOPSIS
RENAME3res NFSPROC3_RENAME(RENAME3args) = 14;
struct RENAME3args {
diropargs3 from;
diropargs3 to;
};
struct RENAME3resok {
wcc_data fromdir_wcc;
wcc_data todir_wcc;
};
struct RENAME3resfail {
wcc_data fromdir_wcc;
wcc_data todir_wcc;
};
union RENAME3res switch (nfsstat3 status) {
case NFS3_OK:
RENAME3resok resok;
default:
RENAME3resfail resfail;
};
DESCRIPTION
Procedure RENAME renames the file identified by from.name
in the directory, from.dir, to to.name in the di- rectory,
to.dir. The operation is required to be atomic to the
client. To.dir and from.dir must reside on the same file
system and server. On entry, the arguments in RENAME3args
are:
from
A diropargs3 structure identifying the source (the file
system object to be re-named):
from.dir
The file handle for the directory from which the
entry is to be renamed.
from.name
The name of the entry that identifies the object to
be renamed. Refer to General comments on filenames
on page 30.
to
A diropargs3 structure identifying the target (the new
name of the object):
to.dir
The file handle for the directory to which the
object is to be renamed.
to.name
The new name for the object. Refer to General
comments on filenames on page 30.
If the directory, to.dir, already contains an entry with
the name, to.name, the source object must be compatible
with the target: either both are non-directories or both
are directories and the target must be empty. If
compatible, the existing target is removed before the
rename occurs. If they are not compatible or if the target
is a directory but not empty, the server should return the
error, NFS3ERR_EXIST.
On successful return, RENAME3res.status is NFS3_OK and
RENAME3res.resok contains:
fromdir_wcc
Weak cache consistency data for the directory,
from.dir.
todir_wcc
Weak cache consistency data for the directory, to.dir.
Otherwise, RENAME3res.status contains the error on failure
and RENAME3res.resfail contains the following:
fromdir_wcc
Weak cache consistency data for the directory,
from.dir.
todir_wcc
Weak cache consistency data for the directory, to.dir.
IMPLEMENTATION
The RENAME operation must be atomic to the client. The
message "to.dir and from.dir must reside on the same file
system on the server, [or the operation will fail]" means
that the fsid fields in the attributes for the directories
are the same. If they reside on different file systems,
the error, NFS3ERR_XDEV, is returned. Even though the
operation is atomic, the status, NFS3ERR_MLINK, may be
returned if the server used a "unlink/link/unlink"
sequence internally.
A file handle may or may not become stale on a rename.
However, server implementors are strongly encouraged to
attempt to keep file handles from becoming stale in this
fashion.
On some servers, the filenames, "." and "..", are illegal
as either from.name or to.name. In addition, neither
from.name nor to.name can be an alias for from.dir. These
servers will return the error, NFS3ERR_INVAL, in these
cases.
If from and to both refer to the same file (they might
be hard links of each other), then RENAME should perform
no action and return NFS3_OK.
Refer to General comments on filenames on page 30.
ERRORS
NFS3ERR_NOENT
NFS3ERR_IO
NFS3ERR_ACCES
NFS3ERR_EXIST
NFS3ERR_XDEV
NFS3ERR_NOTDIR
NFS3ERR_ISDIR
NFS3ERR_INVAL
NFS3ERR_NOSPC
NFS3ERR_ROFS
NFS3ERR_MLINK
NFS3ERR_NAMETOOLONG
NFS3ERR_NOTEMPTY
NFS3ERR_DQUOT
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_NOTSUPP
NFS3ERR_SERVERFAULT
SEE ALSO
REMOVE and LINK.
3.3.15 Procedure 15: LINK - Create Link to an object
SYNOPSIS
LINK3res NFSPROC3_LINK(LINK3args) = 15;
struct LINK3args {
nfs_fh3 file;
diropargs3 link;
};
struct LINK3resok {
post_op_attr file_attributes;
wcc_data linkdir_wcc;
};
struct LINK3resfail {
post_op_attr file_attributes;
wcc_data linkdir_wcc;
};
union LINK3res switch (nfsstat3 status) {
case NFS3_OK:
LINK3resok resok;
default:
LINK3resfail resfail;
};
DESCRIPTION
Procedure LINK creates a hard link from file to link.name,
in the directory, link.dir. file and link.dir must reside
on the same file system and server. On entry, the
arguments in LINK3args are:
file
The file handle for the existing file system object.
link
The location of the link to be created:
link.dir
The file handle for the directory in which the link
is to be created.
link.name
The name that is to be associated with the created
link. Refer to General comments on filenames on page
17.
On successful return, LINK3res.status is NFS3_OK and
LINK3res.resok contains:
file_attributes
The post-operation attributes of the file system object
identified by file.
linkdir_wcc
Weak cache consistency data for the directory,
link.dir.
Otherwise, LINK3res.status contains the error on failure
and LINK3res.resfail contains the following:
file_attributes
The post-operation attributes of the file system object
identified by file.
linkdir_wcc
Weak cache consistency data for the directory,
link.dir.
IMPLEMENTATION
Changes to any property of the hard-linked files are
reflected in all of the linked files. When a hard link is
made to a file, the attributes for the file should have a
value for nlink that is one greater than the value before
the LINK.
The comments under RENAME regarding object and target
residing on the same file system apply here as well. The
comments regarding the target name applies as well. Refer
to General comments on filenames on page 30.
ERRORS
NFS3ERR_IO
NFS3ERR_ACCES
NFS3ERR_EXIST
NFS3ERR_XDEV
NFS3ERR_NOTDIR
NFS3ERR_INVAL
NFS3ERR_NOSPC
NFS3ERR_ROFS
NFS3ERR_MLINK
NFS3ERR_NAMETOOLONG
NFS3ERR_DQUOT
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_NOTSUPP
NFS3ERR_SERVERFAULT
SEE ALSO
SYMLINK, RENAME and FSINFO.
3.3.16 Procedure 16: READDIR - Read From Directory
SYNOPSIS
READDIR3res NFSPROC3_READDIR(READDIR3args) = 16;
struct READDIR3args {
nfs_fh3 dir;
cookie3 cookie;
cookieverf3 cookieverf;
count3 count;
};
struct entry3 {
fileid3 fileid;
filename3 name;
cookie3 cookie;
entry3 *nextentry;
};
struct dirlist3 {
entry3 *entries;
bool eof;
};
struct READDIR3resok {
post_op_attr dir_attributes;
cookieverf3 cookieverf;
dirlist3 reply;
};
struct READDIR3resfail {
post_op_attr dir_attributes;
};
union READDIR3res switch (nfsstat3 status) {
case NFS3_OK:
READDIR3resok resok;
default:
READDIR3resfail resfail;
};
DESCRIPTION
Procedure READDIR retrieves a variable number of entries,
in sequence, from a directory and returns the name and
file identifier for each, with information to allow the
client to request additional directory entries in a
subsequent READDIR request. On entry, the arguments in
READDIR3args are:
dir
The file handle for the directory to be read.
cookie
This should be set to 0 in the first request to read
the directory. On subsequent requests, it should be a
cookie as returned by the server.
cookieverf
This should be set to 0 in the first request to read
the directory. On subsequent requests, it should be a
cookieverf as returned by the server. The cookieverf
must match that returned by the READDIR in which the
cookie was acquired.
count
The maximum size of the READDIR3resok structure, in
bytes. The size must include all XDR overhead. The
server is free to return less than count bytes of
data.
On successful return, READDIR3res.status is NFS3_OK and
READDIR3res.resok contains:
dir_attributes
The attributes of the directory, dir.
cookieverf
The cookie verifier.
reply
The directory list:
entries
Zero or more directory (entry3) entries.
eof
TRUE if the last member of reply.entries is the last
entry in the directory or the list reply.entries is
empty and the cookie corresponded to the end of the
directory. If FALSE, there may be more entries to
read.
Otherwise, READDIR3res.status contains the error on
failure and READDIR3res.resfail contains the following:
dir_attributes
The attributes of the directory, dir.
IMPLEMENTATION
In the NFS version 2 protocol, each directory entry
returned included a cookie identifying a point in the
directory. By including this cookie in a subsequent
READDIR, the client could resume the directory read at any
point in the directory. One problem with this scheme was
that there was no easy way for a server to verify that a
cookie was valid. If two READDIRs were separated by one or
more operations that changed the directory in some way
(for example, reordering or compressing it), it was
possible that the second READDIR could miss entries, or
process entries more than once. If the cookie was no
longer usable, for example, pointing into the middle of a
directory entry, the server would have to either round the
cookie down to the cookie of the previous entry or round
it up to the cookie of the next entry in the directory.
Either way would possibly lead to incorrect results and
the client would be unaware that any problem existed.
In the NFS version 3 protocol, each READDIR request
includes both a cookie and a cookie verifier. For the
first call, both are set to 0. The response includes a
new cookie verifier, with a cookie per entry. For
subsequent READDIRs, the client must present both the
cookie and the corresponding cookie verifier. If the
server detects that the cookie is no longer valid, the
server will reject the READDIR request with the status,
NFS3ERR_BAD_COOKIE. The client should be careful to
avoid holding directory entry cookies across operations
that modify the directory contents, such as REMOVE and
CREATE.
One implementation of the cookie-verifier mechanism might
be for the server to use the modification time of the
directory. This might be overly restrictive, however. A
better approach would be to record the time of the last
directory modification that changed the directory
organization in a way that would make it impossible to
reliably interpret a cookie. Servers in which directory
cookies are always valid are free to use zero as the
verifier always.
The server may return fewer than count bytes of
XDR-encoded entries. The count specified by the client in
the request should be greater than or equal to FSINFO
dtpref.
Since UNIX clients give a special meaning to the fileid
value zero, UNIX clients should be careful to map zero
fileid values to some other value and servers should try
to avoid sending a zero fileid.
ERRORS
NFS3ERR_IO
NFS3ERR_ACCES
NFS3ERR_NOTDIR
NFS3ERR_BAD_COOKIE
NFS3ERR_TOOSMALL
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_SERVERFAULT
SEE ALSO
READDIRPLUS and FSINFO.
3.3.17 Procedure 17: READDIRPLUS - Extended read from directory
SYNOPSIS
READDIRPLUS3res NFSPROC3_READDIRPLUS(READDIRPLUS3args) = 17;
struct READDIRPLUS3args {
nfs_fh3 dir;
cookie3 cookie;
cookieverf3 cookieverf;
count3 dircount;
count3 maxcount;
};
struct entryplus3 {
fileid3 fileid;
filename3 name;
cookie3 cookie;
post_op_attr name_attributes;
post_op_fh3 name_handle;
entryplus3 *nextentry;
};
struct dirlistplus3 {
entryplus3 *entries;
bool eof;
};
struct READDIRPLUS3resok {
post_op_attr dir_attributes;
cookieverf3 cookieverf;
dirlistplus3 reply;
};
struct READDIRPLUS3resfail {
post_op_attr dir_attributes;
};
union READDIRPLUS3res switch (nfsstat3 status) {
case NFS3_OK:
READDIRPLUS3resok resok;
default:
READDIRPLUS3resfail resfail;
};
DESCRIPTION
Procedure READDIRPLUS retrieves a variable number of
entries from a file system directory and returns complete
information about each along with information to allow the
client to request additional directory entries in a
subsequent READDIRPLUS. READDIRPLUS differs from READDIR
only in the amount of information returned for each
entry. In READDIR, each entry returns the filename and
the fileid. In READDIRPLUS, each entry returns the name,
the fileid, attributes (including the fileid), and file
handle. On entry, the arguments in READDIRPLUS3args are:
dir
The file handle for the directory to be read.
cookie
This should be set to 0 on the first request to read a
directory. On subsequent requests, it should be a
cookie as returned by the server.
cookieverf
This should be set to 0 on the first request to read a
directory. On subsequent requests, it should be a
cookieverf as returned by the server. The cookieverf
must match that returned by the READDIRPLUS call in
which the cookie was acquired.
dircount
The maximum number of bytes of directory information
returned. This number should not include the size of
the attributes and file handle portions of the result.
maxcount
The maximum size of the READDIRPLUS3resok structure, in
bytes. The size must include all XDR overhead. The
server is free to return fewer than maxcount bytes of
data.
On successful return, READDIRPLUS3res.status is NFS3_OK
and READDIRPLUS3res.resok contains:
dir_attributes
The attributes of the directory, dir.
cookieverf
The cookie verifier.
reply
The directory list:
entries
Zero or more directory (entryplus3) entries.
eof
TRUE if the last member of reply.entries is the last
entry in the directory or the list reply.entries is
empty and the cookie corresponded to the end of the
directory. If FALSE, there may be more entries to
read.
Otherwise, READDIRPLUS3res.status contains the error on
failure and READDIRPLUS3res.resfail contains the following:
dir_attributes
The attributes of the directory, dir.
IMPLEMENTATION
Issues that need to be understood for this procedure
include increased cache flushing activity on the client
(as new file handles are returned with names which are
entered into caches) and over-the-wire overhead versus
expected subsequent LOOKUP elimination. It is thought that
this procedure may improve performance for directory
browsing where attributes are always required as on the
Apple Macintosh operating system and for MS-DOS.
The dircount and maxcount fields are included as an
optimization. Consider a READDIRPLUS call on a UNIX
operating system implementation for 1048 bytes; the reply
does not contain many entries because of the overhead due
to attributes and file handles. An alternative is to issue
a READDIRPLUS call for 8192 bytes and then only use the
first 1048 bytes of directory information. However, the
server doesn't know that all that is needed is 1048 bytes
of directory information (as would be returned by
READDIR). It sees the 8192 byte request and issues a
VOP_READDIR for 8192 bytes. It then steps through all of
those directory entries, obtaining attributes and file
handles for each entry. When it encodes the result, the
server only encodes until it gets 8192 bytes of results
which include the attributes and file handles. Thus, it
has done a larger VOP_READDIR and many more attribute
fetches than it needed to. The ratio of the directory
entry size to the size of the attributes plus the size of
the file handle is usually at least 8 to 1. The server has
done much more work than it needed to.
The solution to this problem is for the client to provide
two counts to the server. The first is the number of bytes
of directory information that the client really wants,
dircount. The second is the maximum number of bytes in
the result, including the attributes and file handles,
maxcount. Thus, the server will issue a VOP_READDIR for
only the number of bytes that the client really wants to
get, not an inflated number. This should help to reduce
the size of VOP_READDIR requests on the server, thus
reducing the amount of work done there, and to reduce the
number of VOP_LOOKUP, VOP_GETATTR, and other calls done by
the server to construct attributes and file handles.
ERRORS
NFS3ERR_IO
NFS3ERR_ACCES
NFS3ERR_NOTDIR
NFS3ERR_BAD_COOKIE
NFS3ERR_TOOSMALL
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_NOTSUPP
NFS3ERR_SERVERFAULT
SEE ALSO
READDIR.
3.3.18 Procedure 18: FSSTAT - Get dynamic file system information
SYNOPSIS
FSSTAT3res NFSPROC3_FSSTAT(FSSTAT3args) = 18;
struct FSSTAT3args {
nfs_fh3 fsroot;
};
struct FSSTAT3resok {
post_op_attr obj_attributes;
size3 tbytes;
size3 fbytes;
size3 abytes;
size3 tfiles;
size3 ffiles;
size3 afiles;
uint32 invarsec;
};
struct FSSTAT3resfail {
post_op_attr obj_attributes;
};
union FSSTAT3res switch (nfsstat3 status) {
case NFS3_OK:
FSSTAT3resok resok;
default:
FSSTAT3resfail resfail;
};
DESCRIPTION
Procedure FSSTAT retrieves volatile file system state
information. On entry, the arguments in FSSTAT3args are:
fsroot
A file handle identifying a object in the file system.
This is normally a file handle for a mount point for a
file system, as originally obtained from the MOUNT
service on the server.
On successful return, FSSTAT3res.status is NFS3_OK and
FSSTAT3res.resok contains:
obj_attributes
The attributes of the file system object specified in
fsroot.
tbytes
The total size, in bytes, of the file system.
fbytes
The amount of free space, in bytes, in the file
system.
abytes
The amount of free space, in bytes, available to the
user identified by the authentication information in
the RPC. (This reflects space that is reserved by the
file system; it does not reflect any quota system
implemented by the server.)
tfiles
The total number of file slots in the file system. (On
a UNIX server, this often corresponds to the number of
inodes configured.)
ffiles
The number of free file slots in the file system.
afiles
The number of free file slots that are available to the
user corresponding to the authentication information in
the RPC. (This reflects slots that are reserved by the
file system; it does not reflect any quota system
implemented by the server.)
invarsec
A measure of file system volatility: this is the number
of seconds for which the file system is not expected to
change. For a volatile, frequently updated file system,
this will be 0. For an immutable file system, such as a
CD-ROM, this would be the largest unsigned integer. For
file systems that are infrequently modified, for
example, one containing local executable programs and
on-line documentation, a value corresponding to a few
hours or days might be used. The client may use this as
a hint in tuning its cache management. Note however,
this measure is assumed to be dynamic and may change at
any time.
Otherwise, FSSTAT3res.status contains the error on failure
and FSSTAT3res.resfail contains the following:
obj_attributes
The attributes of the file system object specified in
fsroot.
IMPLEMENTATION
Not all implementations can support the entire list of
attributes. It is expected that servers will make a best
effort at supporting all the attributes.
ERRORS
NFS3ERR_IO
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_SERVERFAULT
SEE ALSO
FSINFO.
3.3.19 Procedure 19: FSINFO - Get static file system Information
SYNOPSIS
FSINFO3res NFSPROC3_FSINFO(FSINFO3args) = 19;
const FSF3_LINK = 0x0001;
const FSF3_SYMLINK = 0x0002;
const FSF3_HOMOGENEOUS = 0x0008;
const FSF3_CANSETTIME = 0x0010;
struct FSINFOargs {
nfs_fh3 fsroot;
};
struct FSINFO3resok {
post_op_attr obj_attributes;
uint32 rtmax;
uint32 rtpref;
uint32 rtmult;
uint32 wtmax;
uint32 wtpref;
uint32 wtmult;
uint32 dtpref;
size3 maxfilesize;
nfstime3 time_delta;
uint32 properties;
};
struct FSINFO3resfail {
post_op_attr obj_attributes;
};
union FSINFO3res switch (nfsstat3 status) {
case NFS3_OK:
FSINFO3resok resok;
default:
FSINFO3resfail resfail;
};
DESCRIPTION
Procedure FSINFO retrieves nonvolatile file system state
information and general information about the NFS version
3 protocol server implementation. On entry, the arguments
in FSINFO3args are:
fsroot
A file handle identifying a file object. Normal usage
is to provide a file handle for a mount point for a
file system, as originally obtained from the MOUNT
service on the server.
On successful return, FSINFO3res.status is NFS3_OK and
FSINFO3res.resok contains:
obj_attributes
The attributes of the file system object specified in
fsroot.
rtmax
The maximum size in bytes of a READ request supported
by the server. Any READ with a number greater than
rtmax will result in a short read of rtmax bytes or
less.
rtpref
The preferred size of a READ request. This should be
the same as rtmax unless there is a clear benefit in
performance or efficiency.
rtmult
The suggested multiple for the size of a READ request.
wtmax
The maximum size of a WRITE request supported by the
server. In general, the client is limited by wtmax
since there is no guarantee that a server can handle a
larger write. Any WRITE with a count greater than wtmax
will result in a short write of at most wtmax bytes.
wtpref
The preferred size of a WRITE request. This should be
the same as wtmax unless there is a clear benefit in
performance or efficiency.
wtmult
The suggested multiple for the size of a WRITE
request.
dtpref
The preferred size of a READDIR request.
maxfilesize
The maximum size of a file on the file system.
time_delta
The server time granularity. When setting a file time
using SETATTR, the server guarantees only to preserve
times to this accuracy. If this is {0, 1}, the server
can support nanosecond times, {0, 1000000} denotes
millisecond precision, and {1, 0} indicates that times
are accurate only to the nearest second.
properties
A bit mask of file system properties. The following
values are defined:
FSF_LINK
If this bit is 1 (TRUE), the file system supports
hard links.
FSF_SYMLINK
If this bit is 1 (TRUE), the file system supports
symbolic links.
FSF_HOMOGENEOUS
If this bit is 1 (TRUE), the information returned by
PATHCONF is identical for every file and directory
in the file system. If it is 0 (FALSE), the client
should retrieve PATHCONF information for each file
and directory as required.
FSF_CANSETTIME
If this bit is 1 (TRUE), the server will set the
times for a file via SETATTR if requested (to the
accuracy indicated by time_delta). If it is 0
(FALSE), the server cannot set times as requested.
Otherwise, FSINFO3res.status contains the error on failure
and FSINFO3res.resfail contains the following:
attributes
The attributes of the file system object specified in
fsroot.
IMPLEMENTATION
Not all implementations can support the entire list of
attributes. It is expected that a server will make a best
effort at supporting all the attributes.
The file handle provided is expected to be the file handle
of the file system root, as returned to the MOUNT
operation. Since mounts may occur anywhere within an
exported tree, the server should expect FSINFO requests
specifying file handles within the exported file system.
A server may export different types of file systems with
different attributes returned to the FSINFO call. The
client should retrieve FSINFO information for each mount
completed. Though a server may return different FSINFO
information for different files within a file system,
there is no requirement that a client obtain FSINFO
information for other than the file handle returned at
mount.
The maxfilesize field determines whether a server's
particular file system uses 32 bit sizes and offsets or 64
bit file sizes and offsets. This may affect a client's
processing.
The preferred sizes for requests are nominally tied to an
exported file system mounted by a client. A surmountable
issue arises in that the transfer size for an NFS version
3 protocol request is not only dependent on
characteristics of the file system but also on
characteristics of the network interface, particularly the
maximum transfer unit (MTU). A server implementation can
advertise different transfer sizes (for the fields, rtmax,
rtpref, wtmax, wtpref, and dtpref) depending on the
interface on which the FSINFO request is received. This is
an implementation issue.
ERRORS
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_SERVERFAULT
SEE ALSO
READLINK, WRITE, READDIR, FSSTAT and PATHCONF.
3.3.20 Procedure 20: PATHCONF - Retrieve POSIX information
SYNOPSIS
PATHCONF3res NFSPROC3_PATHCONF(PATHCONF3args) = 20;
struct PATHCONF3args {
nfs_fh3 object;
};
struct PATHCONF3resok {
post_op_attr obj_attributes;
uint32 linkmax;
uint32 name_max;
bool no_trunc;
bool chown_restricted;
bool case_insensitive;
bool case_preserving;
};
struct PATHCONF3resfail {
post_op_attr obj_attributes;
};
union PATHCONF3res switch (nfsstat3 status) {
case NFS3_OK:
PATHCONF3resok resok;
default:
PATHCONF3resfail resfail;
};
DESCRIPTION
Procedure PATHCONF retrieves the pathconf information for
a file or directory. If the FSF_HOMOGENEOUS bit is set in
FSFINFO3resok.properties, the pathconf information will be
the same for all files and directories in the exported
file system in which this file or directory resides. On
entry, the arguments in PATHCONF3args are:
object
The file handle for the file system object.
On successful return, PATHCONF3res.status is NFS3_OK and
PATHCONF3res.resok contains:
obj_attributes
The attributes of the object specified by object.
linkmax
The maximum number of hard links to an object.
name_max
The maximum length of a component of a filename.
no_trunc
If TRUE, the server will reject any request that
includes a name longer than name_max with the error,
NFS3ERR_NAMETOOLONG. If FALSE, any length name over
name_max bytes will be silently truncated to name_max
bytes.
chown_restricted
If TRUE, the server will reject any request to change
either the owner or the group associated with a file if
the caller is not the privileged user. (Uid 0.)
case_insensitive
If TRUE, the server file system does not distinguish
case when interpreting filenames.
case_preserving
If TRUE, the server file system will preserve the case
of a name during a CREATE, MKDIR, MKNOD, SYMLINK,
RENAME, or LINK operation.
Otherwise, PATHCONF3res.status contains the error on
failure and PATHCONF3res.resfail contains the following:
obj_attributes
The attributes of the object specified by object.
IMPLEMENTATION
In some implementations of the NFS version 2 protocol,
pathconf information was obtained at mount time through
the MOUNT protocol. The proper place to obtain it, is as
here, in the NFS version 3 protocol itself.
ERRORS
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_SERVERFAULT
SEE ALSO
LOOKUP, CREATE, MKDIR, SYMLINK, MKNOD, RENAME, LINK and FSINFO.
3.3.21 Procedure 21: COMMIT - Commit cached data on a server to stable storage
SYNOPSIS
COMMIT3res NFSPROC3_COMMIT(COMMIT3args) = 21;
struct COMMIT3args {
nfs_fh3 file;
offset3 offset;
count3 count;
};
struct COMMIT3resok {
wcc_data file_wcc;
writeverf3 verf;
};
struct COMMIT3resfail {
wcc_data file_wcc;
};
union COMMIT3res switch (nfsstat3 status) {
case NFS3_OK:
COMMIT3resok resok;
default:
COMMIT3resfail resfail;
};
DESCRIPTION
プロシージャは、以前UNSTABLEに設定された安定したフィールドを持つWRITEプロシージャの呼び出しで書かれた力や安定したストレージにデータをフラッシュをコミットします。エントリでは、COMMIT3argsの引数は次のとおりです。
file
The file handle for the file to which data is to be
flushed (committed). This must identify a file system
object of type, NF3REG.
offset
The position within the file at which the flush is to
begin. An offset of 0 means to flush data starting at
the beginning of the file.
count
The number of bytes of data to flush. If count is 0, a
flush from offset to the end of file is done.
On successful return, COMMIT3res.status is NFS3_OK and
COMMIT3res.resok contains:
file_wcc
Weak cache consistency data for the file. For a client
that requires only the post-operation file attributes,
these can be found in file_wcc.after.
verf
This is a cookie that the client can use to determine
whether the server has rebooted between a call to WRITE
and a subsequent call to COMMIT. This cookie must be
consistent during a single boot session and must be
unique between instances of the NFS version 3 protocol
server where uncommitted data may be lost.
Otherwise, COMMIT3res.status contains the error on failure
and COMMIT3res.resfail contains the following:
file_wcc
Weak cache consistency data for the file. For a client
that requires only the post-write file attributes,
these can be found in file_wcc.after. Even though the
COMMIT failed, full wcc_data is returned to allow the
client to determine whether the file changed on the
server between calls to WRITE and COMMIT.
IMPLEMENTATION
手順COMMITが操作と意味論でそれをフラッシュし、
ファイルのデータとメタデータのディスクへのディスクを使用してファイルの状態を同期させる
POSIX fsync（2）システムコールに似ています。COMMITが指定されたファイルは、サーバーのディスクに、
サーバー上の任意の非同期データとメタデータをフラッシュし、クライアントに対して同じ操作を実行します。
fsync（2）を同じように、それはいくつか変更されたデータまたは同期させる変更されたデータがあることかもしれません。
データは、サーバーの通常の定期的なバッファ同期活動によって同期されている場合があります。
予期しないエラーが発生した場合を除き、COMMITは常に、NFS3_OKを返します。
COMMITは、（ファイルが完全に書かれている前に、ほとんどのクライアント上のバッファ再生スキームによってトリガされる）ファイルの範囲をフラッシュするためにクライアントのために可能であるという点ではfsync（2）とは異なります。
COMMITのサーバ実装は、合理的に簡単です。
サーバは0とカウントのオフセット0から始まるされている完全なファイルCOMMIT要求を受信した場合、
それはfsyncと同等のものを（）すべき "るファイルです。それ以外の場合は、
オフセットと安定記憶にフラッシュされるようにcountで指定した範囲内でキャッシュされたデータを持っているように手配する必要があります。
両方のケースでは、ファイルに関連付けられたすべてのメタデータは、
返す前に、安定したストレージにフラッシュする必要があります。
サーバ上でフラッシュするものが何もなくなってすることはエラーではありません。
これがフラッシュされるために必要なデータおよびメタデータが既にフラッシュされたり、
最後のサーバー障害時に失われていることを意味します。
COMMITのクライアント実装はもう少し複雑です。安定したストレージにクライアントバッファをコミットしたい理由は2つあります。
最初にクライアントがバッファを再利用したいということです。
このケースでは、オフセットとバッファのカウントがCOMMIT要求時にサーバーに送信されます。
その後、サーバーにフラッシュのオフセットおよびカウントに基づいてキャッシュされたデータを、
フラッシュし、ファイルに関連付けられたメタデータ。
その後、フラッシュとVERF検証のステータスを返します。
COMMITを生成するためのクライアントの他の理由は、終了時に行うことができるよう、
フラッシュの完全なファイルのためのものです。この場合、
クライアントはコミットされていないデータが含まれているこのファイルのバッファのすべてを集めるだろう、
オフセット0と0のカウント、およびそれらのバッファのすべてを、無料でCOMMIT操作を行います。
他のダーティバッファは、通常の方法でサーバに送信されます。
この実装は、クライアント上のバッファ·キャッシュへのいくつかの変更が必要になります。
バッファが安定したUNSTABLEで書き込まれた後、
それがコミット操作によってフラッシュまたはFILE_SYNCまたはDATA_SYNCに安定集合があるWRITE操作で書き込まれるまで、
それはクライアントシステムでダーティとして考慮する必要があります。
これは、データがサーバー上で安定したストレージにフラッシュされる前に解放され再利用されてからバッファを防ぐために行われます。
応答がWRITEまたは予期しないVERFが含まれているCOMMIT操作のいずれかから戻ってきたときに、
クライアントはサーバーにコミットされていないキャッシュされたデータを含むバッファのすべてを再送する必要があります。
実装者にどのようにこれが実行されるまでです。興味のある唯一つのバッファがある場合、
それはおそらく、適切な安定したフラグ付きのWRITE要求に戻って上に送信する必要があります。
複数存在する場合は、それが安定したストレージにサーバー上のすべてのデータをフラッシュするためにCOMMIT操作を再送信して
不安定との安定したセットでのWRITE要求内のバッファのすべてを再送信することができるかもしれません。
これらの再送のタイミングは、実装者に任されている。
上記の説明は、ページキャッシュベースのシステムと同様にバッファ·キャッシュベースのシステムに適用されます。
これらのシステムでは、仮想メモリシステムは、バッファ·キャッシュの代わりに変更する必要があります。
49ページのWRITEの追加コメントを参照してください。
ERRORS
NFS3ERR_IO
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_SERVERFAULT
SEE ALSO
WRITE.
4. Implementation issues
NFSバージョン3プロトコルは、異なるオペレーティングシステムがファイルを共有できるように設計されています。
しかし、それはUNIX環境で設計されて以来、多くの操作は、UNIXファイルシステムの操作に類似したセマンティクスを持っています。
このセクションでは、一般的な実装固有の詳細と意味問題のいくつかを説明します。
手順の説明は、そのプロシージャの特定の実装のコメントを持っています。
論文の数は、NFSバージョン2プロトコルの実装を構築するときに発生する問題を記述する書かれています。
最高の概要紙はまだある[Sandberg]。 [Israel]、[Macklem]、および[Pawlowski]他の実装について説明します。
[X / OpenNFS] NFSバージョン2プロトコルとサポートプロトコルの完全な説明と同様に、
実装の問題と手順やエラー·意味論についての議論を提供しています。
NFSバージョン3プロトコルの実装を構築するときに、NFSバージョン2プロトコルの実装が検出されます。
構築するときの問題の多くが発生しました。
4.1 Multiple version support
The RPC protocol provides explicit support for versioning of
a service. Client and server implementations of NFS version 3
protocol should support both versions, for full backwards
compatibility, when possible. Default behavior of the RPC
binding protocol is the client and server bind using the
highest version number they both support. Client or server
implementations that cannot easily support both versions (for
example, because of memory restrictions) will have to choose
what version to support. The NFS version 2 protocol would be
a safe choice since fully capable clients and servers should
support both versions. However, this choice would need to be
made keeping all requirements in mind.
4.2 Server/client relationship
The NFS version 3 protocol is designed to allow servers to be
as simple and general as possible. Sometimes the simplicity
of the server can be a problem, if the client implements
complicated file system semantics.
For example, some operating systems allow removal of open
files. A process can open a file and, while it is open,
remove it from the directory. The file can be read and
written as long as the process keeps it open, even though the
file has no name in the file system. It is impossible for a
stateless server to implement these semantics. The client
can do some tricks such as renaming the file on remove (to a
hidden name), and only physically deleting it on close. The
NFS version 3 protocol provides sufficient functionality to
implement most file system semantics on a client.
Every NFS version 3 protocol client can also potentially be a
server, and remote and local mounted file systems can be
freely mixed. This leads to some problems when a client
travels down the directory tree of a remote file system and
reaches the mount point on the server for another remote file
system. Allowing the server to follow the second remote mount
would require loop detection, server lookup, and user
revalidation. Instead, both NFS version 2 protocol and NFS
version 3 protocol implementations do not typically let
clients cross a server's mount point. When a client does a
LOOKUP on a directory on which the server has mounted a file
system, the client sees the underlying directory instead of
the mounted directory.
For example, if a server has a file system called /usr and
mounts another file system on /usr/src, if a client mounts
/usr, it does not see the mounted version of /usr/src. A
client could do remote mounts that match the server's mount
points to maintain the server's view. In this example, the
client would also have to mount /usr/src in addition to /usr,
even if they are from the same server.
4.3 Path name interpretation
There are a few complications to the rule that path names are
always parsed on the client. For example, symbolic links
could have different interpretations on different clients.
There is no answer to this problem in this specification.
Another common problem for non-UNIX implementations is the
special interpretation of the pathname, "..", to mean the
parent of a given directory. A future revision of the
protocol may use an explicit flag to indicate the parent
instead - however it is not a problem as many working
non-UNIX implementations exist.
4.4 Permission issues
The NFS version 3 protocol, strictly speaking, does not
define the permission checking used by servers. However, it
is expected that a server will do normal operating system
permission checking using AUTH_UNIX style authentication as
the basis of its protection mechanism, or another stronger
form of authentication such as AUTH_DES or AUTH_KERB. With
AUTH_UNIX authentication, the server gets the client's
effective uid, effective gid, and groups on each call and
uses them to check permission. These are the so-called UNIX
credentials. AUTH_DES and AUTH_KERB use a network name, or
netname, as the basis for identification (from which a UNIX
server derives the necessary standard UNIX credentials).
There are problems with this method that have been solved.
Using uid and gid implies that the client and server share
the same uid list. Every server and client pair must have the
same mapping from user to uid and from group to gid. Since
every client can also be a server, this tends to imply that
the whole network shares the same uid/gid space. If this is
not the case, then it usually falls upon the server to
perform some custom mapping of credentials from one
authentication domain into another. A discussion of
techniques for managing a shared user space or for providing
mechanisms for user ID mapping is beyond the scope of this
specification.
Another problem arises due to the usually stateful open
operation. Most operating systems check permission at open
time, and then check that the file is open on each read and
write request. With stateless servers, the server cannot
detect that the file is open and must do permission checking
on each read and write call. UNIX client semantics of access
permission checking on open can be provided with the ACCESS
procedure call in this revision, which allows a client to
explicitly check access permissions without resorting to
trying the operation. On a local file system, a user can open
a file and then change the permissions so that no one is
allowed to touch it, but will still be able to write to the
file because it is open. On a remote file system, by
contrast, the write would fail. To get around this problem,
the server's permission checking algorithm should allow the
owner of a file to access it regardless of the permission
setting. This is needed in a practical NFS version 3 protocol
server implementation, but it does depart from correct local
file system semantics. This should not affect the return
result of access permissions as returned by the ACCESS
procedure, however.
A similar problem has to do with paging in an executable
program over the network. The operating system usually checks
for execute permission before opening a file for demand
paging, and then reads blocks from the open file. In a local
UNIX file system, an executable file does not need read
permission to execute (pagein). An NFS version 3 protocol
server can not tell the difference between a normal file read
(where the read permission bit is meaningful) and a demand
pagein read (where the server should allow access to the
executable file if the execute bit is set for that user or
group or public). To make this work, the server allows
reading of files if the uid given in the call has either
execute or read permission on the file, through ownership,
group membership or public access. Again, this departs from
correct local file system semantics.
In most operating systems, a particular user (on UNIX, the
uid 0) has access to all files, no matter what permission and
ownership they have. This superuser permission may not be
allowed on the server, since anyone who can become superuser
on their client could gain access to all remote files. A UNIX
server by default maps uid 0 to a distinguished value
(UID_NOBODY), as well as mapping the groups list, before
doing its access checking. A server implementation may
provide a mechanism to change this mapping. This works except
for NFS version 3 protocol root file systems (required for
diskless NFS version 3 protocol client support), where
superuser access cannot be avoided. Export options are used,
on the server, to restrict the set of clients allowed
superuser access.
4.5 Duplicate request cache
典型的なNFSバージョン3プロトコルの障害復旧モデルは、クライアントのタイムアウトを使用し、
サーバーのクラッシュ、ネットワークパーティション、および失われたサーバの応答を処理するために再試行します。
再試行された要求は、元の重複と呼ばれています。
ファイルサーバーのコンテキストで使用される場合において、「冪」とは、操作の種類を区別するために使用することができます。
冪等要求は、サーバが同等の結果（これは実際の変更には、副作用として、ファイルのアクセス時間は、READのために言うかもしれませんが）
で複数回実行することができているものです。いくつかのNFS操作が明らかに非多重呼び出し不変である。
二度目にしようとした場合、彼らが失敗する可能性がありますので、彼らは、
単に特別な注意なしで再処理することはできません。
CREATE要求は、例えば、所有者が書き込み権限を持っていないためにファイルを作成するために使用することができます。
オリジナルが成功した場合は、この要求の複製は成功しません。同様に、ファイルは一度だけ削除することができます。
重複した非べき等の要求を実行することによって引き起こされる副作用（例えば、失われた原因と切り捨て操作は書き込み）
破壊することができます。信頼できないネットワーク·トランスポート（UDP）の一般的な選択肢とステートレス設計の組み合わせにより、
非べき等の要求の破壊的な再生の可能性を意味します。より正確になるが、それは上でもNFSバージョン3プロトコル実装であるため、
非べき等の要求の破壊的な再生の可能性を得られる信頼性のRPCメカニズムの上にNFSバージョン3プロトコルの
本質的なステートレスな設計です。信頼性の高い接続指向のトランスポートは、
自動再確立と接続の切断は、重複する要求の処理（クライアントが要求を再送信し、サーバは潜在的な重複した非べき等の要求に対処する必要があります）が必要です。
ほとんどのNFSv3プロトコルサーバ実装が重複し非べき等の要求の処理のための最近のリクエストのキャッシュを（重複要求キャッシュと呼ばれる）を使用します。
重複要求キャッシュは、リクエストの元の完成状態が記憶された短期記憶のメカニズムを提供し、操作は一度だけ試みた。
このリクエストの重複コピーが受信された場合、元の完了ステータスが返されます。
重複要求キャッシュのメカニズムは、重複するNFSバージョン3プロトコルのリクエストによって引き起こされる破壊的な副作用を減らすのに役立っています。
このメカニズムは、しかしながら、すべての故障モードでこれらの破壊的な副作用に対して保証するものではありません。
ほとんどのサーバーは、RAM内の重複要求キャッシュを格納するので、内容はサーバがクラッシュした場合失われます。
この例外は、おそらくファイルシステム自体は、重複要求キャッシュの状態を共有するために使用される高可用性、
冗長サーバへのアプローチで発生する可能性があります。
キャッシュがサーバの再起動（または高可用性の場合のフェールオーバー）を存続しても、その効果は、そのサイズの関数である。
ネットワークパーティションは、クライアントが対応する要求に対する応答を受信する前にキャッシュ·エントリが再利用されることがあります。
この問題が発生した場合は、重複した要求は、おそらく破壊的な副作用は、新しいものとして処理されます。
重複要求キャッシュの実装および使用の適切な説明は[Juszczak]で見つけることができます。
4.6 File name component handling
Server implementations of NFS version 3 protocol will frequently impose restrictions on the names which can be created. Many servers will also forbid the use of names that
contain certain characters, such as the path component separator used by the server operating system. For example, the UFS file system will reject a name which contains "/",
while "." and ".." are distinguished in UFS, and may not be specified as the name when creating a file system object. The exact error status values return for these errors is
specified in the description of each procedure argument. The values (which conform to NFS version 2 protocol server practice) are not necessarily obvious, nor are they
consistent from one procedure to the next.
4.7 Synchronous modifying operations
Data-modifying operations in the NFS version 3 protocol are synchronous. When a procedure returns to the client, the client can assume that the operation has completed and any
data associated with the request is now on stable storage.
4.8 Stable storage
NFS version 3 protocol servers must be able to recover without data loss from multiple power failures (including cascading power failures, that is, several power failures in
quick succession), operating system failures, and hardware failure of components other than the storage medium itself (for example, disk, nonvolatile RAM).
Some examples of stable storage that are allowable for an NFS server include:
1. Media commit of data, that is, the modified data has
been successfully written to the disk media, for example,
the disk platter.
2. An immediate reply disk drive with battery-backed
on-drive intermediate storage or uninterruptible power
system (UPS).
3. Server commit of data with battery-backed intermediate
storage and recovery software.
4. Cache commit with uninterruptible power system (UPS) and
recovery software.
Conversely, the following are not examples of stable storage:
1. An immediate reply disk drive without battery-backed
on-drive intermediate storage or uninterruptible power
system (UPS).
2. Cache commit without both uninterruptible power system
(UPS) and recovery software.
The only exception to this (introduced in this protocol
revision) is as described under the WRITE procedure on the
handling of the stable bit, and the use of the COMMIT
procedure. It is the use of the synchronous COMMIT procedure
that provides the necessary semantic support in the NFS
version 3 protocol.
4.9 Lookups and name resolution
A common objection to the NFS version 3 protocol is the
philosophy of component-by-component LOOKUP by the client in
resolving a name. The objection is that this is inefficient,
as latencies for component-by-component LOOKUP would be
unbearable.
Implementation practice solves this issue. A name cache,
providing component to file-handle mapping, is kept on the
client to short circuit actual LOOKUP invocations over the
wire. The cache is subject to cache timeout parameters that
bound attributes.
4.10 Adaptive retransmission
Most client implementations use either an exponential
back-off strategy to some maximum retransmission value, or a
more adaptive strategy that attempts congestion avoidance.
Congestion avoidance schemes in NFS request retransmission
are modelled on the work presented in [Jacobson]. [Nowicki]
and [Macklem] describe congestion avoidance schemes to be
applied to the NFS protocol over UDP.
4.11 Caching policies
NFSバージョン3プロトコルは、クライアントまたはサーバー上のキャッシュのポリシーを定義していません。特にありません
クライアントとサーバの間の、また別のクライアントの間に厳密なキャッシュの一貫性を保つためにサポートされています。
いくつかの分散ファイルシステムのキャッシュの同期化とメカニズムの問題についての議論のための[Kazar]を参照してください。
4.12 Stable versus unstable writes
The setting of the stable field in the WRITE arguments, that
is whether or not to do asynchronous WRITE requests, is
straightforward on a UNIX client. If the NFS version 3
protocol client receives a write request that is not marked
as being asynchronous, it should generate the RPC with stable
set to TRUE. If the request is marked as being asynchronous,
the RPC should be generated with stable set to FALSE. If the
response comes back with the committed field set to TRUE, the
client should just mark the write request as done and no
further action is required. If committed is set to FALSE,
indicating that the buffer was not synchronized with the
server's disk, the client will need to mark the buffer in
some way which indicates that a copy of the buffer lives on
the server and that a new copy does not need to be sent to
the server, but that a commit is required.
Note that this algorithm introduces a new state for buffers,
thus there are now three states for buffers. The three states
are dirty, done but needs to be committed, and done. This
extra state on the client will likely require modifications
to the system outside of the NFS version 3 protocol client.
One proposal that was rejected was the addition of a boolean
commit argument to the WRITE operation. It would be used to
indicate whether the server should do a full file commit
after doing the write. This seems as if it could be useful if
the client knew that it was doing the last write on the file.
It is difficult to see how this could be used, given existing
client architectures though.
The asynchronous write opens up the window of problems
associated with write sharing. For example: client A writes
some data asynchronously. Client A is still holding the
buffers cached, waiting to commit them later. Client B reads
the modified data and writes it back to the server. The
server then crashes. When it comes back up, client A issues a
COMMIT operation which returns with a different cookie as
well as changed attributes. In this case, the correct action
may or may not be to retransmit the cached buffers.
Unfortunately, client A can't tell for sure, so it will need
to retransmit the buffers, thus overwriting the changes from
client B. Fortunately, write sharing is rare and the
solution matches the current write sharing situation. Without
using locking for synchronization, the behaviour will be
indeterminate.
In a high availability (redundant system) server
implementation, two cases exist which relate to the verf
changing. If the high availability server implementation
does not use a shared-memory scheme, then the verf should
change on failover, since the unsynchronized data is not
available to the second processor and there is no guarantee
that the system which had the data cached was able to flush
it to stable storage before going down. The client will need
to retransmit the data to be safe. In a shared-memory high
availability server implementation, the verf would not need
to change because the server would still have the cached data
available to it to be flushed. The exact policy regarding the
verf in a shared memory high availability implementation,
however, is up to the server implementor.
4.13 32 bit clients/servers and 64 bit clients/servers
The 64 bit nature of the NFS version 3 protocol introduces
several compatibility problems. The most notable two are
mismatched clients and servers, that is, a 32 bit client and
a 64 bit server or a 64 bit client and a 32 bit server.
The problems of a 64 bit client and a 32 bit server are easy
to handle. The client will never encounter a file that it can
not handle. If it sends a request to the server that the
server can not handle, the server should reject the request
with an appropriate error.
The problems of a 32 bit client and a 64 bit server are much
harder to handle. In this situation, the server does not have
a problem because it can handle anything that the client can
generate. However, the client may encounter a file that it
can not handle. The client will not be able to handle a file
whose size can not be expressed in 32 bits. Thus, the client
will not be able to properly decode the size of the file into
its local attributes structure. Also, a file can grow beyond
the limit of the client while the client is accessing the
file.
The solutions to these problems are left up to the individual
implementor. However, there are two common approaches used to
resolve this situation. The implementor can choose between
them or even can invent a new solution altogether.
The most common solution is for the client to deny access to
any file whose size can not be expressed in 32 bits. This is
probably the safest, but does introduce some strange
semantics when the file grows beyond the limit of the client
while it is being access by that client. The file becomes
inaccessible even while it is being accessed.
The second solution is for the client to map any size greater
than it can handle to the maximum size that it can handle.
Effectively, it is lying to the application program. This
allows the application access as much of the file as possible
given the 32 bit offset restriction. This eliminates the
strange semantic of the file effectively disappearing after
it has been accessed, but does introduce other problems. The
client will not be able to access the entire file.
Currently, the first solution is the recommended solution.
However, client implementors are encouraged to do the best
that they can to reduce the effects of this situation.
5.0 Appendix I: Mount protocol
The changes from the NFS version 2 protocol to the NFS version 3
protocol have required some changes to be made in the MOUNT
protocol. To meet the needs of the NFS version 3 protocol, a
new version of the MOUNT protocol has been defined. This new
protocol satisfies the requirements of the NFS version 3
protocol and addresses several other current market
requirements.
5.1 RPC Information
5.1.1 Authentication
The MOUNT service uses AUTH_NONE in the NULL procedure.
AUTH_UNIX, AUTH_SHORT, AUTH_DES, or AUTH_KERB are used for all other procedures. Other authentication types may be supported in the future.
5.1.2 Constants
These are the RPC constants needed to call the MOUNT service.
They are given in decimal.
PROGRAM 100005
VERSION 3
5.1.3 Transport address
The MOUNT service is normally supported over the TCP and UDP protocols. The rpcbind daemon should be queried for the correct transport address.
5.1.4 Sizes
const MNTPATHLEN = 1024; /* Maximum bytes in a path name */
const MNTNAMLEN = 255; /* Maximum bytes in a name */
const FHSIZE3 = 64; /* Maximum bytes in a V3 file handle */
5.1.5 Basic Data Types
typedef opaque fhandle3<FHSIZE3>;
typedef string dirpath<MNTPATHLEN>;
typedef string name<MNTNAMLEN>;
enum mountstat3 {
MNT3_OK = 0, /* no error */
MNT3ERR_PERM = 1, /* Not owner */
MNT3ERR_NOENT = 2, /* No such file or directory */
MNT3ERR_IO = 5, /* I/O error */
MNT3ERR_ACCES = 13, /* Permission denied */
MNT3ERR_NOTDIR = 20, /* Not a directory */
MNT3ERR_INVAL = 22, /* Invalid argument */
MNT3ERR_NAMETOOLONG = 63, /* Filename too long */
MNT3ERR_NOTSUPP = 10004, /* Operation not supported */
MNT3ERR_SERVERFAULT = 10006 /* A failure on the server */
};
5.2 Server Procedures
The following sections define the RPC procedures supplied by a MOUNT version 3 protocol server. The RPC procedure number is given at the top of the page with the name and version. The SYNOPSIS provides the name of the procedure, the list of the names of the arguments, the list of the names of the results, followed by the XDR argument declarations and results declarations. The information in the SYNOPSIS is specified in RPC Data Description Language as defined in [RFC1014]. The
DESCRIPTION section tells what the procedure is expected to do and how its arguments and results are used. The ERRORS section lists the errors returned for specific types of failures. The IMPLEMENTATION field describes how the procedure is expected to work and how it should be used by clients.
program MOUNT_PROGRAM {
version MOUNT_V3 {
void MOUNTPROC3_NULL(void) = 0;
mountres3 MOUNTPROC3_MNT(dirpath) = 1;
mountlist MOUNTPROC3_DUMP(void) = 2;
void MOUNTPROC3_UMNT(dirpath) = 3;
void MOUNTPROC3_UMNTALL(void) = 4;
exports MOUNTPROC3_EXPORT(void) = 5;
} = 3;
} = 100005;
5.2.0 Procedure 0: Null - Do nothing
SYNOPSIS
void MOUNTPROC3_NULL(void) = 0;
DESCRIPTION
Procedure NULL does not do any work. It is made available
to allow server response testing and timing.
IMPLEMENTATION
It is important that this procedure do no work at all so
that it can be used to measure the overhead of processing
a service request. By convention, the NULL procedure
should never require any authentication. A server may
choose to ignore this convention, in a more secure
implementation, where responding to the NULL procedure
call acknowledges the existence of a resource to an
unauthenticated client.
ERRORS
Since the NULL procedure takes no MOUNT protocol arguments
and returns no MOUNT protocol response, it can not return
a MOUNT protocol error. However, it is possible that some
server implementations may return RPC errors based on
security and authentication requirements.
5.2.1 Procedure 1: MNT - Add mount entry
SYNOPSIS
mountres3 MOUNTPROC3_MNT(dirpath) = 1;
struct mountres3_ok {
fhandle3 fhandle;
int auth_flavors<>;
};
union mountres3 switch (mountstat3 fhs_status) {
case MNT_OK:
mountres3_ok mountinfo;
default:
void;
};
DESCRIPTION
Procedure MNT maps a pathname on the server to a file
handle. The pathname is an ASCII string that describes a
directory on the server. If the call is successful
(MNT3_OK), the server returns an NFS version 3 protocol
file handle and a vector of RPC authentication flavors
that are supported with the client's use of the file
handle (or any file handles derived from it). The
authentication flavors are defined in Section 7.2 and
section 9 of [RFC1057].
IMPLEMENTATION
If mountres3.fhs_status is MNT3_OK, then
mountres3.mountinfo contains the file handle for the
directory and a list of acceptable authentication
flavors. This file handle may only be used in the NFS
version 3 protocol. This procedure also results in the
server adding a new entry to its mount list recording that
this client has mounted the directory. AUTH_UNIX
authentication or better is required.
ERRORS
MNT3ERR_NOENT
MNT3ERR_IO
MNT3ERR_ACCES
MNT3ERR_NOTDIR
MNT3ERR_NAMETOOLONG
5.2.2 Procedure 2: DUMP - Return mount entries
SYNOPSIS
mountlist MOUNTPROC3_DUMP(void) = 2;
typedef struct mountbody *mountlist;
struct mountbody {
name ml_hostname;
dirpath ml_directory;
mountlist ml_next;
};
DESCRIPTION
Procedure DUMP returns the list of remotely mounted file
systems. The mountlist contains one entry for each client
host name and directory pair.
IMPLEMENTATION
This list is derived from a list maintained on the server
of clients that have requested file handles with the MNT
procedure. Entries are removed from this list only when a
client calls the UMNT or UMNTALL procedure. Entries may
become stale if a client crashes and does not issue either
UMNT calls for all of the file systems that it had
previously mounted or a UMNTALL to remove all entries that
existed for it on the server.
ERRORS
There are no MOUNT protocol errors which can be returned
from this procedure. However, RPC errors may be returned
for authentication or other RPC failures.
5.2.3 Procedure 3: UMNT - Remove mount entry
SYNOPSIS
void MOUNTPROC3_UMNT(dirpath) = 3;
DESCRIPTION
Procedure UMNT removes the mount list entry for the
directory that was previously the subject of a MNT call
from this client. AUTH_UNIX authentication or better is
required.
IMPLEMENTATION
Typically, server implementations have maintained a list
of clients which have file systems mounted. In the past,
this list has been used to inform clients that the server
was going to be shutdown.
ERRORS
There are no MOUNT protocol errors which can be returned
from this procedure. However, RPC errors may be returned
for authentication or other RPC failures.
5.2.4 Procedure 4: UMNTALL - Remove all mount entries
SYNOPSIS
void MOUNTPROC3_UMNTALL(void) = 4;
DESCRIPTION
Procedure UMNTALL removes all of the mount entries for
this client previously recorded by calls to MNT. AUTH_UNIX
authentication or better is required.
IMPLEMENTATION
This procedure should be used by clients when they are
recovering after a system shutdown. If the client could
not successfully unmount all of its file systems before
being shutdown or the client crashed because of a software
or hardware problem, there may be servers which still have
mount entries for this client. This is an easy way for the
client to inform all servers at once that it does not have
any mounted file systems. However, since this procedure
is generally implemented using broadcast RPC, it is only
of limited usefullness.
ERRORS
There are no MOUNT protocol errors which can be returned
from this procedure. However, RPC errors may be returned
for authentication or other RPC failures.
5.2.5 Procedure 5: EXPORT - Return export list
SYNOPSIS
exports MOUNTPROC3_EXPORT(void) = 5;
typedef struct groupnode *groups;
struct groupnode {
name gr_name;
groups gr_next;
};
typedef struct exportnode *exports;
struct exportnode {
dirpath ex_dir;
groups ex_groups;
exports ex_next;
};
DESCRIPTION
Procedure EXPORT returns a list of all the exported file
systems and which clients are allowed to mount each one.
The names in the group list are implementation-specific
and cannot be directly interpreted by clients. These names
can represent hosts or groups of hosts.
IMPLEMENTATION
This procedure generally returns the contents of a list of
shared or exported file systems. These are the file
systems which are made available to NFS version 3 protocol
clients.
ERRORS
There are no MOUNT protocol errors which can be returned
from this procedure. However, RPC errors may be returned
for authentication or other RPC failures.
6.0 Appendix II: Lock manager protocol
Because the NFS version 2 protocol as well as the NFS version 3
protocol is stateless, an additional Network Lock Manager (NLM)
protocol is required to support locking of NFS-mounted files.
The NLM version 3 protocol, which is used with the NFS version 2
protocol, is documented in [X/OpenNFS].
Some of the changes in the NFS version 3 protocol require a
new version of the NLM protocol. This new protocol is the NLM
version 4 protocol. The following table summarizes the
correspondence between versions of the NFS protocol and NLM
protocol.
NFS and NLM protocol compatibility
+---------+---------+
| NFS | NLM |
| Version | Version |
+===================+
| 2 | 1,3 |
+---------+---------+
| 3 | 4 |
+---------+---------+
This appendix only discusses the differences between the NLM
version 3 protocol and the NLM version 4 protocol. As in the
NFS version 3 protocol, almost all the names in the NLM version
4 protocol have been changed to include a version number. This
appendix does not discuss changes that consist solely of a name
change.
6.1 RPC Information
6.1.1 Authentication
The NLM service uses AUTH_NONE in the NULL procedure.
AUTH_UNIX, AUTH_SHORT, AUTH_DES, and AUTH_KERB are used for all other procedures. Other authentication types may be supported in the future.
6.1.2 Constants
These are the RPC constants needed to call the NLM service.
They are given in decimal.
PROGRAM 100021
VERSION 4
6.1.3 Transport Address
The NLM service is normally supported over the TCP and UDP
protocols. The rpcbind daemon should be queried for the
correct transport address.
6.1.4 Basic Data Types
uint64
typedef unsigned hyper uint64;
int64
typedef hyper int64;
uint32
typedef unsigned long uint32;
int32
typedef long int32;
These types are new for the NLM version 4 protocol. They are
the same as in the NFS version 3 protocol.
nlm4_stats
enum nlm4_stats {
NLM4_GRANTED = 0,
NLM4_DENIED = 1,
NLM4_DENIED_NOLOCKS = 2,
NLM4_BLOCKED = 3,
NLM4_DENIED_GRACE_PERIOD = 4,
NLM4_DEADLCK = 5,
NLM4_ROFS = 6,
NLM4_STALE_FH = 7,
NLM4_FBIG = 8,
NLM4_FAILED = 9
};
Nlm4_stats indicates the success or failure of a call. This
version contains several new error codes, so that clients can
provide more precise failure information to applications.
NLM4_GRANTED
The call completed successfully.
NLM4_DENIED
The call failed. For attempts to set a lock, this status
implies that if the client retries the call later, it may
succeed.
NLM4_DENIED_NOLOCKS
The call failed because the server could not allocate the
necessary resources.
NLM4_BLOCKED
Indicates that a blocking request cannot be granted
immediately. The server will issue an NLMPROC4_GRANTED
callback to the client when the lock is granted.
NLM4_DENIED_GRACE_PERIOD
The call failed because the server is reestablishing old
locks after a reboot and is not yet ready to resume normal
service.
NLM4_DEADLCK
The request could not be granted and blocking would cause
a deadlock.
NLM4_ROFS
The call failed because the remote file system is
read-only. For example, some server implementations might
not support exclusive locks on read-only file systems.
NLM4_STALE_FH
The call failed because it uses an invalid file handle.
This can happen if the file has been removed or if access
to the file has been revoked on the server.
NLM4_FBIG
The call failed because it specified a length or offset
that exceeds the range supported by the server.
NLM4_FAILED
The call failed for some reason not already listed. The
client should take this status as a strong hint not to
retry the request.
nlm4_holder
struct nlm4_holder {
bool exclusive;
int32 svid;
netobj oh;
uint64 l_offset;
uint64 l_len;
};
This structure indicates the holder of a lock. The exclusive
field tells whether the holder has an exclusive lock or a
shared lock. The svid field identifies the process that is
holding the lock. The oh field is an opaque object that
identifies the host or process that is holding the lock. The
l_len and l_offset fields identify the region that is locked.
The only difference between the NLM version 3 protocol and
the NLM version 4 protocol is that in the NLM version 3
protocol, the l_len and l_offset fields are 32 bits wide,
while they are 64 bits wide in the NLM version 4 protocol.
nlm4_lock
struct nlm4_lock {
string caller_name<LM_MAXSTRLEN>;
netobj fh;
netobj oh;
int32 svid;
uint64 l_offset;
uint64 l_len;
};
This structure describes a lock request. The caller_name
field identifies the host that is making the request. The fh
field identifies the file to lock. The oh field is an opaque
object that identifies the host or process that is making the
request, and the svid field identifies the process that is
making the request. The l_offset and l_len fields identify
the region of the file that the lock controls. A l_len of 0
means "to end of file".
There are two differences between the NLM version 3 protocol
and the NLM version 4 protocol versions of this structure.
First, in the NLM version 3 protocol, the length and offset
are 32 bits wide, while they are 64 bits wide in the NLM
version 4 protocol. Second, in the NLM version 3 protocol,
the file handle is a fixed-length NFS version 2 protocol file
handle, which is encoded as a byte count followed by a byte
array. In the NFS version 3 protocol, the file handle is
already variable-length, so it is copied directly into the fh
field. That is, the first four bytes of the fh field are the
same as the byte count in an NFS version 3 protocol nfs_fh3.
The rest of the fh field contains the byte array from the NFS
version 3 protocol nfs_fh3.
nlm4_share
struct nlm4_share {
string caller_name<LM_MAXSTRLEN>;
netobj fh;
netobj oh;
fsh4_mode mode;
fsh4_access access;
};
This structure is used to support DOS file sharing. The
caller_name field identifies the host making the request.
The fh field identifies the file to be operated on. The oh
field is an opaque object that identifies the host or process
that is making the request. The mode and access fields
specify the file-sharing and access modes. The encoding of fh
is a byte count, followed by the file handle byte array. See
the description of nlm4_lock for more details.
6.2 NLM Procedures
The procedures in the NLM version 4 protocol are semantically the same as those in the NLM version 3 protocol. The only
semantic difference is the addition of a NULL procedure that can be used to test for server responsiveness. The procedure
names with _MSG and _RES suffixes denote asynchronous messages; for these the void response implies no reply. A
syntactic change is that the procedures were renamed to avoid name conflicts with the values of nlm4_stats. Thus the
procedure definition is as follows.
version NLM4_VERS {
void
NLMPROC4_NULL(void) = 0;
nlm4_testres
NLMPROC4_TEST(nlm4_testargs) = 1;
nlm4_res
NLMPROC4_LOCK(nlm4_lockargs) = 2;
nlm4_res
NLMPROC4_CANCEL(nlm4_cancargs) = 3;
nlm4_res
NLMPROC4_UNLOCK(nlm4_unlockargs) = 4;
nlm4_res
NLMPROC4_GRANTED(nlm4_testargs) = 5;
void
NLMPROC4_TEST_MSG(nlm4_testargs) = 6;
void
NLMPROC4_LOCK_MSG(nlm4_lockargs) = 7;
void
NLMPROC4_CANCEL_MSG(nlm4_cancargs) = 8;
void
NLMPROC4_UNLOCK_MSG(nlm4_unlockargs) = 9;
void
NLMPROC4_GRANTED_MSG(nlm4_testargs) = 10;
void
NLMPROC4_TEST_RES(nlm4_testres) = 11;
void
NLMPROC4_LOCK_RES(nlm4_res) = 12;
void
NLMPROC4_CANCEL_RES(nlm4_res) = 13;
void
NLMPROC4_UNLOCK_RES(nlm4_res) = 14;
void
NLMPROC4_GRANTED_RES(nlm4_res) = 15;
nlm4_shareres
NLMPROC4_SHARE(nlm4_shareargs) = 20;
nlm4_shareres
NLMPROC4_UNSHARE(nlm4_shareargs) = 21;
nlm4_res
NLMPROC4_NM_LOCK(nlm4_lockargs) = 22;
void
NLMPROC4_FREE_ALL(nlm4_notify) = 23;
} = 4;
6.2.0 Procedure 0: NULL - Do nothing
SYNOPSIS
void NLMPROC4_NULL(void) = 0;
DESCRIPTION
The NULL procedure does no work. It is made available in
all RPC services to allow server response testing and
timing.
IMPLEMENTATION
It is important that this procedure do no work at all so
that it can be used to measure the overhead of processing
a service request. By convention, the NULL procedure
should never require any authentication.
ERRORS
It is possible that some server implementations may return
RPC errors based on security and authentication
requirements.
6.3 Implementation issues
6.3.1 64-bit offsets and lengths
Some NFS version 3 protocol servers can only support requests where the file offset or length fits in 32 or
fewer bits. For these servers, the lock manager will have the same restriction. If such a lock manager receives a
request that it cannot handle (because the offset or length uses more than 32 bits), it should return the error, NLM4_FBIG.
6.3.2 File handles
The change in the file handle format from the NFS version 2 protocol to the NFS version 3 protocol complicates the
lock manager. First, the lock manager needs some way to tell when an NFS version 2 protocol file handle refers to
the same file as an NFS version 3 protocol file handle.
(This is assuming that the lock manager supports both NLM version 3 protocol clients and NLM version 4 protocol
clients.) Second, if the lock manager runs the file handle through a hashing function, the hashing function may need
to be retuned to work with NFS version 3 protocol file handles as well as NFS version 2 protocol file handles.
7.0 Appendix III: Bibliography
[Corbin] Corbin, John, "The Art of Distributed
Programming-Programming Techniques for Remote
Procedure Calls." Springer-Verlag, New York, New
York. 1991. Basic description of RPC and XDR
and how to program distributed applications
using them.
[Glover] Glover, Fred, "TNFS Protocol Specification,"
Trusted System Interest Group, Work in
Progress.
[Israel] Israel, Robert K., Sandra Jett, James Pownell,
George M. Ericson, "Eliminating Data Copies in
UNIX-based NFS Servers," Uniforum Conference
Proceedings, San Francisco, CA,
February 27 - March 2, 1989. Describes two
methods for reducing data copies in NFS server
code.
[Jacobson] Jacobson, V., "Congestion Control and
Avoidance," Proc. ACM SIGCOMM `88, Stanford, CA,
August 1988. The paper describing improvements
to TCP to allow use over Wide Area Networks and
through gateways connecting networks of varying
capacity. This work was a starting point for the
NFS Dynamic Retransmission work.
[Juszczak] Juszczak, Chet, "Improving the Performance and
Correctness of an NFS Server," USENIX Conference
Proceedings, USENIX Association, Berkeley, CA,
June 1990, pages 53-63. Describes reply cache
implementation that avoids work in the server by
handling duplicate requests. More important,
though listed as a side-effect, the reply cache
aids in the avoidance of destructive
non-idempotent operation re-application --
improving correctness.
[Kazar] Kazar, Michael Leon, "Synchronization and Caching
Issues in the Andrew File System," USENIX Conference
Proceedings, USENIX Association, Berkeley, CA,
Dallas Winter 1988, pages 27-36. A description
of the cache consistency scheme in AFS.
Contrasted with other distributed file systems.
[Macklem] Macklem, Rick, "Lessons Learned Tuning the
4.3BSD Reno Implementation of the NFS Protocol,"
Winter USENIX Conference Proceedings, USENIX
Association, Berkeley, CA, January 1991.
Describes performance work in tuning the 4.3BSD
Reno NFS implementation. Describes performance
improvement (reduced CPU loading) through
elimination of data copies.
[Mogul] Mogul, Jeffrey C., "A Recovery Protocol for Spritely
NFS," USENIX File System Workshop Proceedings,
Ann Arbor, MI, USENIX Association, Berkeley, CA,
May 1992. Second paper on Spritely NFS proposes
a lease-based scheme for recovering state of
consistency protocol.
[Nowicki] Nowicki, Bill, "Transport Issues in the Network
File System," ACM SIGCOMM newsletter Computer
Communication Review, April 1989. A brief
description of the basis for the dynamic
retransmission work.
[Pawlowski] Pawlowski, Brian, Ron Hixon, Mark Stein, Joseph
Tumminaro, "Network Computing in the UNIX and
IBM Mainframe Environment," Uniforum `89 Conf.
Proc., (1989) Description of an NFS server
implementation for IBM's MVS operating system.
[RFC1014] Sun Microsystems, Inc., "XDR: External Data
Representation Standard", RFC 1014,
Sun Microsystems, Inc., June 1987.
Specification for canonical format for data
exchange, used with RPC.
[RFC1057] Sun Microsystems, Inc., "RPC: Remote Procedure
Call Protocol Specification", RFC 1057,
Sun Microsystems, Inc., June 1988.
Remote procedure protocol specification.
[RFC1094] Sun Microsystems, Inc., "Network Filesystem
Specification", RFC 1094, Sun Microsystems, Inc.,
March 1989. NFS version 2 protocol
specification.
[Sandberg] Sandberg, R., D. Goldberg, S. Kleiman, D. Walsh,
B. Lyon, "Design and Implementation of the Sun
Network Filesystem," USENIX Conference
Proceedings, USENIX Association, Berkeley, CA,
Summer 1985. The basic paper describing the
SunOS implementation of the NFS version 2
protocol, and discusses the goals, protocol
specification and trade-offs.
[Srinivasan] Srinivasan, V., Jeffrey C. Mogul, "Spritely
NFS: Implementation and Performance of Cache
Consistency Protocols", WRL Research Report
89/5, Digital Equipment Corporation Western
Research Laboratory, 100 Hamilton Ave., Palo
Alto, CA, 94301, May 1989. This paper analyzes
the effect of applying a Sprite-like consistency
protocol applied to standard NFS. The issues of
recovery in a stateful environment are covered
in [Mogul].
[X/OpenNFS] X/Open Company, Ltd., X/Open CAE Specification:
Protocols for X/Open Internetworking: XNFS,
X/Open Company, Ltd., Apex Plaza, Forbury Road,
Reading Berkshire, RG1 1AX, United Kingdom,
1991. This is an indispensable reference for
NFS version 2 protocol and accompanying
protocols, including the Lock Manager and the
Portmapper.
[X/OpenPCNFS] X/Open Company, Ltd., X/Open CAE Specification:
Protocols for X/Open Internetworking: (PC)NFS,
Developer's Specification, X/Open Company, Ltd.,
Apex Plaza, Forbury Road, Reading Berkshire, RG1
1AX, United Kingdom, 1991. This is an
indispensable reference for NFS version 2
protocol and accompanying protocols, including
the Lock Manager and the Portmapper.
8. Security Considerations
Since sensitive file data may be transmitted or received
from a server by the NFS protocol, authentication, privacy,
and data integrity issues should be addressed by implementations
of this protocol.
As with the previous protocol revision (version 2), NFS
version 3 defers to the authentication provisions of the
supporting RPC protocol [RFC1057], and assumes that data
privacy and integrity are provided by underlying transport
layers as available in each implementation of the protocol.
See section 4.4 for a discussion relating to file access
permissions.
9. Acknowledgements
This description of the protocol is derived from an original
document written by Brian Pawlowski and revised by Peter
Staubach. This protocol is the result of a co-operative
effort that comprises the contributions of Geoff Arnold,
Brent Callaghan, John Corbin, Fred Glover, Chet Juszczak,
Mike Eisler, John Gillono, Dave Hitz, Mike Kupfer, Rick
Macklem, Ron Minnich, Brian Pawlowski, David Robinson, Rusty
Sandberg, Craig Schamp, Spencer Shepler, Carl Smith, Mark
Stein, Peter Staubach, Tom Talpey, Rob Thurlow, and Mark
Wittle.
10. Authors' Addresses
Address comments related to this protocol to:
nfs3@eng.sun.com
Brent Callaghan
Sun Microsystems, Inc.
2550 Garcia Avenue
Mailstop UMTV05-44
Mountain View, CA 94043-1100
Phone: 1-415-336-1051
Fax: 1-415-336-6015
EMail: brent.callaghan@eng.sun.com
Brian Pawlowski
Network Appliance Corp.
319 North Bernardo Ave.
Mountain View, CA 94043
Phone: 1-415-428-5136
Fax: 1-415-428-5151
EMail: beepy@netapp.com
Peter Staubach
Sun Microsystems, Inc.
2550 Garcia Avenue
Mailstop UMTV05-44
Mountain View, CA 94043-1100
Phone: 1-415-336-5615
Fax: 1-415-336-6015
EMail: peter.staubach@eng.sun.com
原文はこのへんをどうぞ
Network Working Group B. Callaghan
Request for Comments: 1813 B. Pawlowski
Category: Informational P. Staubach
Sun Microsystems, Inc.
June 1995
NFS Version 3 Protocol Specification
Status of this Memo
This memo provides information for the Internet community.
This memo does not specify an Internet standard of any kind.
Distribution of this memo is unlimited.
IESG Note
Internet Engineering Steering Group comment: please note that
the IETF is not involved in creating or maintaining this
specification. This is the significance of the specification
not being on the standards track.
Abstract
This paper describes the NFS version 3 protocol. This paper is
provided so that people can write compatible implementations.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Scope of the NFS version 3 protocol . . . . . . . . . . 4
1.2 Useful terms . . . . . . . . . . . . . . . . . . . . . . 5
1.3 Remote Procedure Call . . . . . . . . . . . . . . . . . 5
1.4 External Data Representation . . . . . . . . . . . . . . 5
1.5 Authentication and Permission Checking . . . . . . . . . 7
1.6 Philosophy . . . . . . . . . . . . . . . . . . . . . . . 8
1.7 Changes from the NFS version 2 protocol . . . . . . . . 11
2. RPC Information . . . . . . . . . . . . . . . . . . . . . 14
2.1 Authentication . . . . . . . . . . . . . . . . . . . . . 14
2.2 Constants . . . . . . . . . . . . . . . . . . . . . . . 14
2.3 Transport address . . . . . . . . . . . . . . . . . . . 14
2.4 Sizes . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.5 Basic Data Types . . . . . . . . . . . . . . . . . . . . 15
2.6 Defined Error Numbers . . . . . . . . . . . . . . . . . 17
3. Server Procedures . . . . . . . . . . . . . . . . . . . . 27
3.1 General comments on attributes . . . . . . . . . . . . . 29
3.2 General comments on filenames . . . . . . . . . . . . . 30
3.3.0 NULL: Do nothing . . . . . . . . . . . . . . . . . . . . 31
3.3.1 GETATTR: Get file attributes . . . . . . . . . . . . . . 32
3.3.2 SETATTR: Set file attributes . . . . . . . . . . . . . . 33
3.3.3 LOOKUP: Lookup filename . . . . . . . . . . . . . . . . 37
3.3.4 ACCESS: Check access permission . . . . . . . . . . . . 40
3.3.5 READLINK: Read from symbolic link . . . . . . . . . . . 44
3.3.6 READ: Read from file . . . . . . . . . . . . . . . . . . 46
3.3.7 WRITE: Write to file . . . . . . . . . . . . . . . . . . 49
3.3.8 CREATE: Create a file . . . . . . . . . . . . . . . . . 54
3.3.9 MKDIR: Create a directory . . . . . . . . . . . . . . . 58
3.3.10 SYMLINK: Create a symbolic link . . . . . . . . . . . . 61
3.3.11 MKNOD: Create a special device . . . . . . . . . . . . . 63
3.3.12 REMOVE: Remove a file . . . . . . . . . . . . . . . . . 67
3.3.13 RMDIR: Remove a directory . . . . . . . . . . . . . . . 69
3.3.14 RENAME: Rename a file or directory . . . . . . . . . . . 71
3.3.15 LINK: Create link to an object . . . . . . . . . . . . . 74
3.3.16 READDIR: Read From directory . . . . . . . . . . . . . . 76
3.3.17 READDIRPLUS: Extended read from directory . . . . . . . 80
3.3.18 FSSTAT: Get dynamic file system information . . . . . . 84
3.3.19 FSINFO: Get static file system information . . . . . . . 86
3.3.20 PATHCONF: Retrieve POSIX information . . . . . . . . . . 90
3.3.21 COMMIT: Commit cached data on a server to stable storage 92
4. Implementation issues . . . . . . . . . . . . . . . . . . 96
4.1 Multiple version support . . . . . . . . . . . . . . . . 96
4.2 Server/client relationship . . . . . . . . . . . . . . . 96
4.3 Path name interpretation . . . . . . . . . . . . . . . . 97
4.4 Permission issues . . . . . . . . . . . . . . . . . . . 98
4.5 Duplicate request cache . . . . . . . . . . . . . . . . 99
4.6 File name component handling . . . . . . . . . . . . . . 101
4.7 Synchronous modifying operations . . . . . . . . . . . . 101
4.8 Stable storage . . . . . . . . . . . . . . . . . . . . . 101
4.9 Lookups and name resolution . . . . . . . . . . . . . . 102
4.10 Adaptive retransmission . . . . . . . . . . . . . . . . 102
4.11 Caching policies . . . . . . . . . . . . . . . . . . . . 102
4.12 Stable versus unstable writes. . . . . . . . . . . . . . 103
4.13 32 bit clients/servers and 64 bit clients/servers. . . . 104
5. Appendix I: Mount protocol . . . . . . . . . . . . . . . . 106
5.1 RPC Information . . . . . . . . . . . . . . . . . . . . 106
5.1.1 Authentication . . . . . . . . . . . . . . . . . . . . 106
5.1.2 Constants . . . . . . . . . . . . . . . . . . . . . . 106
5.1.3 Transport address . . . . . . . . . . . . . . . . . . 106
5.1.4 Sizes . . . . . . . . . . . . . . . . . . . . . . . . 106
5.1.5 Basic Data Types . . . . . . . . . . . . . . . . . . . 106
5.2 Server Procedures . . . . . . . . . . . . . . . . . . . 107
5.2.0 NULL: Do nothing . . . . . . . . . . . . . . . . . . . 108
5.2.1 MNT: Add mount entry . . . . . . . . . . . . . . . . . 109
5.2.2 DUMP: Return mount entries . . . . . . . . . . . . . . 110
5.2.3 UMNT: Remove mount entry . . . . . . . . . . . . . . . 111
5.2.4 UMNTALL: Remove all mount entries . . . . . . . . . . 112
5.2.5 EXPORT: Return export list . . . . . . . . . . . . . . 113
6. Appendix II: Lock manager protocol . . . . . . . . . . . . 114
6.1 RPC Information . . . . . . . . . . . . . . . . . . . . 114
6.1.1 Authentication . . . . . . . . . . . . . . . . . . . . 114
6.1.2 Constants . . . . . . . . . . . . . . . . . . . . . . 114
6.1.3 Transport Address . . . . . . . . . . . . . . . . . . 115
6.1.4 Basic Data Types . . . . . . . . . . . . . . . . . . . 115
6.2 NLM Procedures . . . . . . . . . . . . . . . . . . . . . 118
6.2.0 NULL: Do nothing . . . . . . . . . . . . . . . . . . . 120
6.3 Implementation issues . . . . . . . . . . . . . . . . . 120
6.3.1 64-bit offsets and lengths . . . . . . . . . . . . . . 120
6.3.2 File handles . . . . . . . . . . . . . . . . . . . . . 120
7. Appendix III: Bibliography . . . . . . . . . . . . . . . . 122
8. Security Considerations . . . . . . . . . . . . . . . . . 125
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . 125
10. Authors' Addresses . . . . . . . . . . . . . . . . . . . . 126
1. Introduction
SunのNFSプロトコルは、ネットワークを介して共有ファイルシステムへの
透過的なリモートアクセスを提供します。
NFSプロトコルは、マシン、オペレーティングシステム、ネットワークアーキテクチャ、およびトランスポートプロトコルに依存しないように設計されています。
この独立性は、リモートプロシージャコール（RPC）外部データ表現（XDR）の上に構築されたプリミティブの使用によって達成されています。
NFSバージョン2プロトコルの実装では、パーソナルコンピュータからスーパーコンピュータまで、
様々なマシンに存在します。
NFSプロトコルの初期バージョンはネットワークファイルシステムプロトコル仕様[RFC1094]で
指定されています。
初期の実装の説明は、[Sandberg]で見つけることができます。
サポートする、MOUNTプロトコルは、クライアントがローカルファイルシステム内のポイントへの
リモートディレクトリツリーをアタッチできるよう
オペレーティング·システム固有の機能を実行します。
マウントプロセスは、サーバがエクスポート制御を介してクライアントの制限されたセットへの
リモートアクセス権限を付与することができます。
NFS環境で使用するロック·マネージャは、ファイルのロックをサポートしています。
ネットワークロックマネージャ（NLM）プロトコルは、
別のプロトコルにファイルロックの本質的にステートフルな側面を分離します。
上記のプロトコルとその実装の完全な記述は[X/OpenNFS]で閲覧可能です。
このドキュメントの目的は、次のとおりです。
・NFSバージョン3プロトコルを示す。
・意図された実装を、注釈や説明を介してプロトコルのセマンティクスを説明する。
・MOUNT version3プロトコルを示す。
・NLM version3プロトコルとNLM version4プロトコル間の変更点を簡単に説明する。
標準のテキストは、RPCの手順と引数と結果は、オーバーザワイヤープロトコルを定義し、
これらの手順の意味の説明です。インプリメンテーションの実践を記述する材料は、
プロトコル仕様の理解を助けると考えられるいくつかの実装上の問題と解決策について説明します。
それはすべての実装を記述することはできませんと、
NFSバージョン3プロトコルのUNIXオペレーティング·システムのインプリメンテーションは、
最も頻繁に例を提供するために使用されます。
ことを考えると、実装の議論はオーバーザワイヤープロトコル自体の記述の
権威を負うものではありません。
1.1 Scope of the NFS version 3 protocol
このリビジョンのNFSプロトコルは、新しい要件に対応しています。
大きなファイルやファイルシステムをサポートする必要性は、
64ビットのファイルサイズとオフセットを可能にする拡張機能を求めている。
リビジョンは、サーバー上で実行するアクセスチェックのサポートを追加することにより、
セキュリティが強化されます。パフォーマンスの変更は、3つのタイプがあります。
1.ファイル操作の特定のセットの過線パケットの数は、
このように変更された属性を取得するコールの数を減少し、
すべての操作でファイルの属性を返すことによって低減されます。
2. NFSv2プロトコルの書き込みの同期定義が原因で
書き込みスループットのボトルネックは、
NFSサーバが危険な書き込みを行うことができるようにサポートを追加することで解決されました。
危険な操作が戻る前に安定したストレージにコミットされていないどの書き込みされているが
書き込まれます。この仕様はこれらの危険は、信頼性の高い方法で安定したストレージへの
書き込みをコミットするためのメソッドを定義します。
3。転送サイズに関する制限が緩和されました。
RPCのプロトコルの複数のバージョンをサポートする機能は、
NFSバージョン3プロトコルの実装者は、
NFSバージョン2プロトコルの既存のインストールベースを使用して
クライアントとの後方互換性を提供するサーバーを定義実装することができます。
拡張機能は、既存のNFSプロトコルと[Sandberg]が持続するで説明され、
NFSプロトコルの設計上の特徴のほとんどの進化を表してここで説明する。
この改正により導入された変更の詳細な概要については、
11ページのNFSバージョン2プロトコルからの変更点を参照してください。
1.2 Useful terms
In this specification, a "server" is a machine that provides
resources to the network; a "client" is a machine that accesses
resources over the network; a "user" is a person logged in on a
client; an "application" is a program that executes on a client.
1.3 Remote Procedure Call
SunRPCの仕様は、リモートサービスへのプロシージャ指向のインタフェースを提供します。
各サーバーは、一連の手順でプログラムを提供しています。
NFSサービスは、そのようなプログラムです。ホストアドレスの組み合わせは、
プログラム番号、バージョン番号、プロシージャ番号が
1つのリモート·サービス·プロシージャを指定します。
サーバーは、異なるプロトコルのバージョン番号を使用して、プログラムの複数のバージョンをサポートすることができます。
NFSプロトコルは、それが潜在的に多くの基本的なトランスポートプロトコルに
使用することができるので、その下のレベルから信頼性の任意の特定の
レベルを必要としないように設計されています。
NFSサービスは、下位レベルのネットワークとトランスポート·プロトコル上に
抽象化を提供するRPCに基づいています。
このドキュメントの残りの部分は、NFS環境は[RFC1057]で指定されている
Sun RPCの上に実装されていると仮定しています。完全な議論は[Corbin]で見つけられます。
1.4 External Data Representation
外部データ表現（XDR）仕様は、ネットワーク上のデータ型のセットを表すための
標準的な方法を提供します。これは、異なる、通信しているマシン上で異なるバイトオーダー、
構造アライメント、およびデータ型の表現の問題を解決します。
このドキュメントでは、RPCデータ記述言語は、
NFSサーバーが提供するRPCサービスのプロシージャのそれぞれに
XDR形式のパラメータと結果を指定するために使用されています。
RPCデータ記述言語は、Cプログラミング言語の宣言に似ています。
いくつかの新しい構文が追加されました。
The notation:
string name[SIZE];
string data<DSIZE>;
バイトをDSIZEまでの可変サイズのブロックであるsizeバイトの固定サイズのブロックである名前、
およびデータは、定義されています。この表記は、
最大の固定最大の要素の数が可変固定長配列と配列を示しています。
指定されていないサイズの可変長の定義は、フィールドの最大サイズが存在しないことを意味します。
The discriminated union definition:
union example switch (enum status) {
case OK:
struct {
filename file1;
filename file2;
integer count;
}
case ERROR:
struct {
errstat error;
integer errno;
}
default:
void;
}
ネットワークを介してまず最初に、ステータスと呼ばれる列挙型である構造体を定義します。
状態の値がOKであれば、ネットワークの次のものは、file1、file2を含む構造体である、
とカウントされます。ステータスの値がERRORの場合は、他に、
ネットワーク上の次のものがエラーとerrnoを含む構造になります。
状態の値がOKでもERRORのどちらである場合は、構造中にそれ以上データがない。
XDR型、ハイパーは、8バイト（64ビット）の量である。これは、整数型と同じ方法で使用されています。たとえば、次のように
hyper foo;
unsigned hyper bar;
barは8バイトの符号なしの値ですがfooは、8バイトの符号付きの値です。
RPC / XDRコンパイラは、RPCデータ記述言語入力から、
クライアントとサーバーのスタブを生成するために存在しますが、
NFSの実装では、その使用を必要としません。
XDRによって定義されたデータの標準的なネットワークのために同等の符号化と復号化を
提供する任意のソフトウェアは他のNFSの実装と相互運用するために使用することができます。
XDRは、[RFC1014]で説明されます。
1.5 Authentication and Permission Checking
RPCプロトコルは、呼び出しのたびに認証パラメータ用のスロットが含まれています。
認証パラメータの内容は、サーバーとクライアントによって使用される
uthenticationのタイプによって決定されます。
サーバーは、一度認証にはいくつかの異なった属性をサポートすることができます。
AUTH_NONE属性は、認証情報が渡されない場合はnull認証を提供します。
AUTH_UNIX属性はUNIX形式のユーザーID、グループID、およびそれぞれの呼び出しでグループが用意されています。
AUTH_DES属性は、公開鍵方式を介して交換されたセッションキーを使用して
ネットワーク全体の名前に基づくDES-暗号化された認証パラメータを提供します。
AUTH_KERB属性はケルベロス秘密鍵を介して交換されたセッションキーを使用して
ネットワーク全体の名前に基づいてDES暗号化された認証パラメータを提供します。
NFSサーバーは、それぞれのリモート要求でRPC認証情報から資格を取ることによって
アクセス権をチェックします。たとえば、認証のAUTH_UNIX属性を使用して、
サーバーが呼び出しのたびにユーザの実効ユーザID、実効グループIDとグループを取得し、
アクセスを確認するためにそれらを使用しています。ユーザーIDとグループIDを使用すると、
クライアントとサーバが同じIDリストを共有したり、ローカルユーザーとグループIDの
マッピングを行うのどちらかことを意味します。サーバーとクライアントは、
これらの一貫したユーザIDを実装していないサイトやグループIDのスペースのために、
ユーザからuidに、グループからGIDへのマッピングに同意する必要があります。
実際には、そのようなマッピングは、通常、静的マッピングの方式や、
マウント時にクライアントからユーザによって確立されたマッピングに従って、サーバーで実行されます。
認証のAUTH_DESとAUTH_KERBスタイルはネットワーク全体の名前に基づいています。
それはAUTH_DESの場合には、DES暗号化鍵と公開鍵を使用してセキュリティを強化を提供し、
AUTH_KERBケースでDES暗号化とKerberos秘密鍵（およびチケット）。
再び、サーバとクライアントは、ネットワーク上の特定の名前のIDに同意しなければなりませんが、
アイデンティティへのマッピング名がAUTH_UNIXでuidとgidのマッピングがより独立した
複数のオペレーティングシステムです。認証パラメータが暗号化されているため、
また、悪意のあるユーザーが別のユーザーのネットワークパスワードまたは
そのユーザーのふりをする秘密鍵を知っている必要があります。
同様に、サーバがサーバのふりをすると、ネットワークパスワードを知る必要がありますように
また、暗号化されている検証を返します。
NULL手順は、通常は認証を必要としません。
1.6 Philosophy
この仕様は、クライアントがサーバーにアクセスすることによって
オーバーザワイヤープロトコルであるNFSバージョン3プロトコルを定義します。
プロトコルは、サーバーのファイル·リソースへの、明確に定義されたインタフェースを提供します。
クライアントまたはサーバーがプロトコルを実装し、
NFSバージョン3プロトコルで定義されているものにローカルファイルシステムの
セマンティクスとアクションのマッピングを提供します。
実装では、与えられた環境では、NFSバージョン3プロトコルで定義されているすべての操作と
セマンティクスをサポートできる程度に応じて、様々な程度に異なる場合があります。
実装が存在し、NFSバージョン3プロトコルのさまざまな側面を説明するために使用されていますが、
プロトコルの仕様自体は、クライアントがサーバーのリソースにアクセスする方法の最終的な説明です。
NFSバージョン3プロトコルがオペレーティングシステムに依存しないように設計されているので、
それは必ずしも既存のシステムのセマンティクスと一致しません。
サーバ実装は、プロトコルを支援する最善の努力を行なうことが期待されています。
サーバが特定のプロトコル手順をサポートすることができない場合は、
操作がサポートされていないことを示すエラー、NFS3ERR_NOTSUPを返す可能性があります。
たとえば、多くのオペレーティングシステムはハードリンクの概念をサポートしていません。
ハードリンクをサポートすることができないサーバはLINK要求に応答してNFS3ERR_NOTSUPを返す必要があります。
FSINFOは、プロパティのビットマップで最も一般的にサポートされていない手順を説明します。
また、サーバーはネイティブ特定の操作をサポートしていないかもしれませんが、
優れた機能を提供するために、NFSバージョン3プロトコル実装でそれをエミュレートすることができます。
いくつかのケースでは、サーバはほとんどのセマンティクスをサポートしますが、全てではありません。
たとえば、fattr構造のctimeのフィールドはファイルの属性が最後に変更された時刻を示します。
多くのシステムでは、この情報を保持しません。このケースでは、
GETATTR操作をサポートしていないのではなく、サーバはctimeの代わりに最後に更新された時刻を返すことによって、
それをシミュレートすることができます。
クライアント上の可能性のある副作用のために属性情報をシミュレートするとき、
サーバは慎重でなければなりません。たとえば、多くのクライアントは、
キャッシュの一貫性スキームのための基礎として、ファイルの修正時刻を使用しています。。
NFSサーバは愚かであり、NFSクライアントはスマートです。
それはアプリケーションやユーザーにとって有用であるファイルへのアクセスメソッドに
サーバーが提供する一般的なファイルアクセスを変換するために必要な作業を行うクライアントです。
上記のLINKの例では、サーバーからNFS3ERR_NOTSUPエラーを受信し、
UNIXクライアントは、リンク要求が成功したかの合理的なエラーを返したような、
アプリケーションに見えるようにするために必要な回復を行うだろう。
一般的に、それは回復するクライアントの負担です。
NFSバージョン3プロトコルはステートレスなサーバの実装を前提としています。
ステートレスサーバが正しく機能するためには、そのクライアントの
いずれかに関する状態を維持する必要がないことを意味します。
ステートレスサーバがクラッシュしたときにステートフル·サーバ上の明確な利点を持っています。
ステートレスサーバーで、クライアントは、サーバーが応答するまでだけ要求を再試行する必要があります。
クライアントは、サーバがクラッシュしたことを知る必要はありません。
99ページの重複要求キャッシュの追加のコメントを参照してください。
サーバーが有用であるためには、不揮発性の状態を保持します：ファイルシステムに格納されているデータを。
変更されたデータのフラッシュについてはNFSバージョン3プロトコルの設計上の前提条件、
安定したストレージにデータの損失が発生する可能性のある故障モードの数を減らすことができます。
この方法では、NFSバージョン3プロトコルの実装は、ネットワークの一時的な障害を含む一時的な障害を耐えることができます。
一般的には、NFSバージョン3プロトコルのサーバ実装は安定貯蔵自体の非一時的な障害に耐えることができません。
しかし、このような問題に対処しようとしたフォールトトレラントの実装が存在する。
これはNFSバージョン3プロトコルサーバは重要でない状態を維持できないということではありません。
多くの場合、サーバは、パフォーマンスを向上させるために、以前の操作に関する状態（キャッシュ）を維持します。
たとえば、クライアント要求が、クライアントはシーケンシャルリードを行っていると、
次のクライアント要求がサーバーのデータ·キャッシュから満たされるお読みになることを見越して、
サーバーのデータ·キャッシュへのファイルの次のブロックの先読みの引き金となるかもしれない、
READの代わりに、ディスクから。サーバ上の先読みクライアントの要求でサーバのディスクI / Oをオーバーラップすることにより、
パフォーマンスを向上させます。ここで重要な点は、先読みブロックは正しいサーバ動作の必要がないことです。
サーバがクラッシュして読み取られたバッファのメモリキャッシュを失った場合、
回復は再起動時に簡単です - クライアントはサーバーのディスクからデータを取得する読み取り操作を続行します。
NFSプロトコルのほとんどのデータ変更は、同期操作です。
そのデータはクライアントへの手順に戻りを変更するとき、つまり、クライアントは、
操作が完了し、要求に関連付けられたすべての変更されたデータが安定したストレージ上にあることを仮定することができます。
後者の情報は、通常、メタデータと呼ばれている - たとえば、同期クライアントの書き込み要求はデータ·ブロック、
ファイルシステム情報ブロック、およびファイル属性情報を更新するために、
サーバーを引き起こす可能性があります。 WRITE操作が完了すると、クライアントは、
書き込みデータが安全であることを想定し、それを破棄することができます。
これは、サーバのステートレスな性質の非常に重要な部分です。
サーバがクライアントに返す前に、安定したストレージにダーティ·データをフラッシュしなかった場合、
クライアントは変更されたデータを破棄しても安全だったかを知る方法はありません。
プロシージャを変更する以下のデータが同期しています：WRITE（FILE_SYNCに設定された安定したフラグを持つ）、
CREATE、MKDIR、SYMLINK、MKNOD、REMOVE、RMDIR、RENAME、LINK、およびコミットします。
NFSバージョン3プロトコルでは、WRITEプロシージャがCOMMIT手順と組み合わせて使用される場合、
安全な非同期は、サーバー上の書き込みを紹介しています。
COMMIT手順は、クライアントが安定したストレージにサーバー上で以前の非同期書き込み要求から
データをフラッシュすると、データを再送する必要があるかどうかを検出する方法を提供します。
49ページのWRITEの手順の説明を参照してください（92ページ）コミットします。
LOOKUP手順は、多成分のファイル名（パス名）を横断するためにクライアントによって使用されています。
検索するための各コールは、パスの1つのセグメントを解決するために使用されています。
単一のセグメントにLOOKUPを制限する理由は二つあります：それは階層的なファイル名と、
クライアントとサーバーがファイル·システムへのパス名の異なるマッピングがあるかもしれませんするための共通フォーマットを標準化することは困難です。
これは、いずれかのクライアントがファイル·システム·アタッチメント·ポイントでパス名を突破しなければならない、
またはサーバがクライアントのファイルシステムの接続点について知っている必要があることを含意するでしょう。
NFSバージョン3プロトコル実装では、階層を構築するためにマウントを使用して階層的なファイル名のスペースを構築するクライアントです。
このようなオートマウンタとしてサポートユーティリティ、まだクライアントのマウントプロセスによって駆動されている間に
ファイルの名前空間の共有、一貫したイメージを管理する方法を提供しています。
クライアントは、様々な方法でキャッシュを行うことができます。
NFSバージョン2プロトコルを用いる一般的な方法は、
時間ベースのクライアント·サーバ·キャッシュの一貫性メカニズムを実装することであった。
それは、NFSバージョン3プロトコル実装が同様のメカニズムを使用すると予想されます。
NFSバージョン3プロトコルでは、明示的な属性チェックを排除するために追加の属性情報の形で、
いくつかの明示的なサポートを持っています。しかし、キャッシュが必要でなく、
プロトコルで定義された任意のキャッシュポリシーではありませんされています。
どちらも、NFSバージョン2プロトコルもNFSバージョン3プロトコルは、
厳密なクライアント·サーバの一貫性（と、暗に、クライアントのキャッシュ一貫性）を維持するための手段を提供していません。
1.7 Changes from the NFS Version 2 Protocol
ROOTとWRITECACHE手順が削除されました。MKNOD手順は、CREATEのオーバーロードを排除する
特殊ファイルの作成を可能にするために定義されています。
クライアント上のキャッシュが定義されても、NFSバージョン3プロトコルによって決まりますが、
追加情報とヒントは、より効果的にキャッシュを管理するために
キャッシュを実装するクライアントを許可するためのプロトコルに追加されましたされていません。
操作が属性キャッシュの検証に使用され、後続のGETATTRを最適化するために完了した後、
ファイルまたはディレクトリの属性に影響を与えるの手順は、新しい属性を返すことができます。
さらに、ターゲット·オブジェクトが存在するディレクトリを変更する操作は、
古いものと新しい属性を返すクライアントは、よりインテリジェントなキャッシュを
無効にする手順を実装できるようにするディレクトリ。
ACCESSのプロシージャがサーバー上でチェックするアクセス許可を提供し、
FSSTATプロシージャは、ファイルシステムに関する動的な情報を返しますが、
FSINFO手順はファイルシステムとサーバに関するスタティック情報を返し、
READDIRPLUS手順はディレクトリエントリに加えて、ファイルハンドルと属性を返し、
PATHCONF手順は、ファイルに関するPOSIXのpathconf情報を返します。
以下のNFSバージョン2プロトコルとNFSバージョン3プロトコルの間に重要な変更のリストです。
File handle size
The file handle has been increased to a variable-length array of 64 bytes maximum from a fixed array of 32
bytes. This addresses some known requirements for a slightly larger file handle size. The file handle was
converted from fixed length to variable length to reduce local storage and network bandwidth requirements
for systems which do not utilize the full 64 bytes of length.
Maximum data sizes
The maximum size of a data transfer used in the READ and WRITE procedures is now set by values in the FSINFO
return structure. In addition, preferred transfer sizes are returned by FSINFO. The protocol does not place any
artificial limits on the maximum transfer sizes.
Filenames and pathnames are now specified as strings of variable length. The actual length restrictions are
determined by the client and server implementations as appropriate. The protocol does not place any
artificial limits on the length. The error, NFS3ERR_NAMETOOLONG, is provided to allow the server to
return an indication to the client that it received a pathname that was too long for it to handle.
Error return
Error returns in some instances now return data (for example, attributes). nfsstat3 now defines the full set
of errors that can be returned by a server. No other values are allowed.
File type
The file type now includes NF3CHR and NF3BLK for special files. Attributes for these types include
subfields for UNIX major and minor devices numbers. NF3SOCK and NF3FIFO are now defined for sockets and
fifos in the file system.
File attributes
The blocksize (the size in bytes of a block in the file) field has been removed. The mode field no longer
contains file type information. The size and fileid fields have been widened to eight-byte unsigned
integers from four-byte integers. Major and minor device information is now presented in a distinct
structure. The blocks field name has been changed to used and now contains the total number of bytes used by
the file. It is also an eight-byte unsigned integer.
Set file attributes
In the NFS version 2 protocol, the settable attributes were represented by a subset of the file attributes
structure; the client indicated those attributes which were not to be modified by setting the corresponding
field to -1, overloading some unsigned fields. The set file attributes structure now uses a discriminated
union for each field to tell whether or how to set that field. The atime and mtime fields can be set to either
the server's current time or a time supplied by the client.
LOOKUP
The LOOKUP return structure now includes the attributes for the directory searched.
ACCESS
An ACCESS procedure has been added to allow an explicit over-the-wire permissions check. This addresses known
problems with the superuser ID mapping feature in many server implementations (where, due to mapping of root
user, unexpected permission denied errors could occur while reading from or writing to a file). This also
removes the assumption which was made in the NFS version 2 protocol that access to files was based
solely on UNIX style mode bits.
READ
The reply structure includes a Boolean that is TRUE if the end-of-file was encountered during the READ. This
allows the client to correctly detect end-of-file.
WRITE
The beginoffset and totalcount fields were removed from the WRITE arguments. The reply now includes a count so
that the server can write less than the requested amount of data, if required. An indicator was added to
the arguments to instruct the server as to the level of cache synchronization that is required by the client.
CREATE
An exclusive flag and a create verifier was added for
the exclusive creation of regular files.
MKNOD
This procedure was added to support the creation of
special files. This avoids overloading fields of CREATE
as was done in some NFS version 2 protocol
implementations.
READDIR
The READDIR arguments now include a verifier to allow
the server to validate the cookie. The cookie is now a
64 bit unsigned integer instead of the 4 byte array
which was used in the NFS version 2 protocol. This
will help to reduce interoperability problems.
READDIRPLUS
This procedure was added to return file handles and
attributes in an extended directory list.
FSINFO
FSINFO was added to provide nonvolatile information
about a file system. The reply includes preferred and
maximum read transfer size, preferred and maximum write
transfer size, and flags stating whether links or
symbolic links are supported. Also returned are
preferred transfer size for READDIR procedure replies,
server time granularity, and whether times can be set
in a SETATTR request.
FSSTAT
FSSTAT was added to provide volatile information about
a file system, for use by utilities such as the Unix
system df command. The reply includes the total size
and free space in the file system specified in bytes,
the total number of files and number of free file slots
in the file system, and an estimate of time between
file system modifications (for use in cache consistency
checking algorithms).
COMMIT
The COMMIT procedure provides the synchronization
mechanism to be used with asynchronous WRITE
operations.
2. RPC Information
2.1 Authentication
The NFS service uses AUTH_NONE in the NULL procedure. AUTH_UNIX, AUTH_DES, or AUTH_KERB are used for all other procedures. Other authentication types may be supported in the future.
2.2 Constants
These are the RPC constants needed to call the NFS Version 3 service. They are given in decimal.
PROGRAM 100003
VERSION 3
2.3 Transport address
The NFS protocol is normally supported over the TCP and UDP protocols. It uses port 2049, the same as the NFS version 2 protocol.
2.4 Sizes
These are the sizes, given in decimal bytes, of various XDR structures used in the NFS version 3 protocol:
NFS3_FHSIZE 64
The maximum size in bytes of the opaque file handle.
NFS3_COOKIEVERFSIZE 8
The size in bytes of the opaque cookie verifier passed by READDIR and READDIRPLUS.
NFS3_CREATEVERFSIZE 8
The size in bytes of the opaque verifier used for exclusive CREATE.
NFS3_WRITEVERFSIZE 8
The size in bytes of the opaque verifier used for asynchronous WRITE.
2.5 Basic Data Types
The following XDR definitions are basic definitions that are used in other structures.
uint64
typedef unsigned hyper uint64;
int64
typedef hyper int64;
uint32
typedef unsigned long uint32;
int32
typedef long int32;
filename3
typedef string filename3<>;
nfspath3
typedef string nfspath3<>;
fileid3
typedef uint64 fileid3;
cookie3
typedef uint64 cookie3;
cookieverf3
typedef opaque cookieverf3[NFS3_COOKIEVERFSIZE];
createverf3
typedef opaque createverf3[NFS3_CREATEVERFSIZE];
writeverf3
typedef opaque writeverf3[NFS3_WRITEVERFSIZE];
uid3
typedef uint32 uid3;
gid3
typedef uint32 gid3;
size3
typedef uint64 size3;
offset3
typedef uint64 offset3;
mode3
typedef uint32 mode3;
count3
typedef uint32 count3;
nfsstat3
enum nfsstat3 {
NFS3_OK = 0,
NFS3ERR_PERM = 1,
NFS3ERR_NOENT = 2,
NFS3ERR_IO = 5,
NFS3ERR_NXIO = 6,
NFS3ERR_ACCES = 13,
NFS3ERR_EXIST = 17,
NFS3ERR_XDEV = 18,
NFS3ERR_NODEV = 19,
NFS3ERR_NOTDIR = 20,
NFS3ERR_ISDIR = 21,
NFS3ERR_INVAL = 22,
NFS3ERR_FBIG = 27,
NFS3ERR_NOSPC = 28,
NFS3ERR_ROFS = 30,
NFS3ERR_MLINK = 31,
NFS3ERR_NAMETOOLONG = 63,
NFS3ERR_NOTEMPTY = 66,
NFS3ERR_DQUOT = 69,
NFS3ERR_STALE = 70,
NFS3ERR_REMOTE = 71,
NFS3ERR_BADHANDLE = 10001,
NFS3ERR_NOT_SYNC = 10002,
NFS3ERR_BAD_COOKIE = 10003,
NFS3ERR_NOTSUPP = 10004,
NFS3ERR_TOOSMALL = 10005,
NFS3ERR_SERVERFAULT = 10006,
NFS3ERR_BADTYPE = 10007,
NFS3ERR_JUKEBOX = 10008
};
The nfsstat3 type is returned with every procedure's results except for the NULL procedure. A value of NFS3_OK indicates that
the call completed successfully. Any other value indicates that some error occurred on the call, as identified by the error
code. Note that the precise numeric encoding must be followed.
No other values may be returned by a server. Servers are expected to make a best effort mapping of error conditions to
the set of error codes defined. In addition, no error precedences are specified by this specification. Error
precedences determine the error value that should be returned when more than one error applies in a given situation. The error
precedence will be determined by the individual server implementation. If the client requires specific error
precedences, it should check for the specific errors for itself.
2.6 Defined Error Numbers
A description of each defined error follows:
NFS3_OK
Indicates the call completed successfully.
NFS3ERR_PERM
Not owner. The operation was not allowed because the caller is either not a privileged user (root) or not the owner of the target of the operation.
NFS3ERR_NOENT
No such file or directory. The file or directory name specified does not exist.
NFS3ERR_IO
I/O error. A hard error (for example, a disk error) occurred while processing the requested operation.
NFS3ERR_NXIO
I/O error. No such device or address.
NFS3ERR_ACCES
Permission denied. The caller does not have the correct permission to perform the requested operation. Contrast this with NFS3ERR_PERM, which restricts itself to owner or privileged user permission failures.
NFS3ERR_EXIST
File exists. The file specified already exists.
NFS3ERR_XDEV
Attempt to do a cross-device hard link.
NFS3ERR_NODEV
No such device.
NFS3ERR_NOTDIR
Not a directory. The caller specified a non-directory in a directory operation.
NFS3ERR_ISDIR
Is a directory. The caller specified a directory in a non-directory operation.
NFS3ERR_INVAL
Invalid argument or unsupported argument for an operation. Two examples are attempting a READLINK on an object other than a symbolic link or attempting to
SETATTR a time field on a server that does not support this operation.
NFS3ERR_FBIG
File too large. The operation would have caused a file to grow beyond the server's limit.
NFS3ERR_NOSPC
No space left on device. The operation would have caused the server's file system to exceed its limit.
NFS3ERR_ROFS
Read-only file system. A modifying operation was attempted on a read-only file system.
NFS3ERR_MLINK
Too many hard links.
NFS3ERR_NAMETOOLONG
The filename in an operation was too long.
NFS3ERR_NOTEMPTY
An attempt was made to remove a directory that was not
empty.
NFS3ERR_DQUOT
Resource (quota) hard limit exceeded. The user's resource limit on the server has been exceeded.
NFS3ERR_STALE
Invalid file handle. The file handle given in the arguments was invalid.
The file referred to by that file handle no longer exists or access to it has been revoked.
NFS3ERR_REMOTE
Too many levels of remote in path. The file handle given in the arguments referred to a file on a non-local file system on the server.
NFS3ERR_BADHANDLE
Illegal NFS file handle. The file handle failed internal consistency checks.
NFS3ERR_NOT_SYNC
Update synchronization mismatch was detected during a SETATTR operation.
NFS3ERR_BAD_COOKIE
READDIR or READDIRPLUS cookie is stale.
NFS3ERR_NOTSUPP
Operation is not supported.
NFS3ERR_TOOSMALL
Buffer or request is too small.
NFS3ERR_SERVERFAULT
An error occurred on the server which does not map to any of the legal NFS version 3 protocol error values.
The client should translate this into an appropriate error. UNIX clients may choose to translate this to EIO.
NFS3ERR_BADTYPE
An attempt was made to create an object of a type not supported by the server.
NFS3ERR_JUKEBOX
The server initiated the request, but was not able to complete it in a timely fashion.
The client should wait and then try the request with a new RPC transaction ID.
For example, this error should be returned from a server that supports hierarchical storage and receives a request to process a file that has been migrated.
In this case, the server should start the immigration process and respond to client with this error.
ftype3
enum ftype3 {
NF3REG = 1,
NF3DIR = 2,
NF3BLK = 3,
NF3CHR = 4,
NF3LNK = 5,
NF3SOCK = 6,
NF3FIFO = 7
};
The enumeration, ftype3, gives the type of a file. The type, NF3REG, is a regular file, NF3DIR is a directory,
NF3BLK is a block special device file, NF3CHR is a character special device file, NF3LNK is a symbolic link,
NF3SOCK is a socket, and NF3FIFO is a named pipe. Note that the precise enum encoding must be followed.
specdata3
struct specdata3 {
uint32 specdata1;
uint32 specdata2;
};
The interpretation of the two words depends on the type of file system object.
For a block special (NF3BLK) or character special (NF3CHR) file, specdata1 and specdata2 are the major and minor device numbers, respectively.
(This is obviously a UNIX-specific interpretation.) For all other file types,
these two elements should either be set to 0 or the values should be agreed upon by the client and server.
If the client and server do not agree upon the values, the client should treat these fields as if they are set to 0.
This data field is returned as part of the fattr3 structure and so is available from all replies returning attributes.
Since these fields are otherwise unused for objects which are not devices, out of band information can be passed from the server to the client.
However, once again, both the server and the client must agree on the values passed.
nfs_fh3
struct nfs_fh3 {
opaque data<NFS3_FHSIZE>;
};
The nfs_fh3 is the variable-length opaque object returned by the server on LOOKUP, CREATE, SYMLINK, MKNOD, LINK, or READDIRPLUS operations,
which is used by the client on subsequent operations to reference the file.
The file handle contains all the information the server needs to distinguish an individual file.
To the client, the file handle is opaque. The client stores file handles for use in a later request and can compare two file handles
from the same server for equality by doing a byte-by-byte comparison, but cannot otherwise interpret the contents of file handles.
If two file handles from the same server are equal, they must refer to the same file, but if they are not equal,
no conclusions can be drawn. Servers should try to maintain a one-to-one correspondence between file handles and files,
but this is not required. Clients should use file handle comparisons only to improve performance, not for correct behavior.
Servers can revoke the access provided by a file handle at any time.
If the file handle passed in a call refers to a file system object that no longer exists on the server or access for that file handle has been revoked,
the error, NFS3ERR_STALE, should be returned.
nfstime3
struct nfstime3 {
uint32 seconds;
uint32 nseconds;
};
The nfstime3 structure gives the number of seconds and nanoseconds since midnight January 1, 1970 Greenwich Mean Time.
It is used to pass time and date information.
The times associated with files are all server times except in the case of a SETATTR operation where the client can explicitly set the file time.
A server converts to and from local time when processing time values, preserving as much accuracy as possible.
If the precision of timestamps stored for a file is less than that
defined by NFS version 3 protocol, loss of precision can occur.
An adjunct time maintenance protocol is recommended to reduce client and server time skew.
fattr3
struct fattr3 {
ftype3 type;
mode3 mode;
uint32 nlink;
uid3 uid;
gid3 gid;
size3 size;
size3 used;
specdata3 rdev;
uint64 fsid;
fileid3 fileid;
nfstime3 atime;
nfstime3 mtime;
nfstime3 ctime;
};
This structure defines the attributes of a file system object.
It is returned by most operations on an object; in the case of operations that affect two objects (for example, a MKDIR that modifies the target directory attributes and defines new attributes for the newly created directory), the attributes for both may be returned. In some cases, the attributes are returned in the structure, wcc_data, which is defined below; in other cases the attributes are returned alone. The main changes from the NFS version 2 protocol are that many of the fields have been widened and the major/minor device information is now presented in a distinct structure rather than being packed into a word.
The fattr3 structure contains the basic attributes of a file.
All servers should support this set of attributes even if they have to simulate some of the fields. Type is the type of the file. Mode is the protection mode bits. Nlink is the number of hard links to the file - that is, the number of different names for the same file. Uid is the user ID of the owner of the file.
Gid is the group ID of the group of the file. Size is the size of the file in bytes. Used is the number of bytes of disk space that the file actually uses (which can be smaller than the size because the file may have holes or it may be larger due to fragmentation). Rdev describes the device file if the file type is NF3CHR or NF3BLK - see specdata3 on page 20. Fsid is the file system identifier for the file system. Fileid is a number which uniquely identifies the file within its file system (on UNIX
this would be the inumber). Atime is the time when the file data was last accessed. Mtime is the time when the file data was last modified. Ctime is the time when the attributes of the file were last changed. Writing to the file changes the ctime in addition to the mtime.
The mode bits are defined as follows:
0x00800 Set user ID on execution.
0x00400 Set group ID on execution.
0x00200 Save swapped text (not defined in POSIX).
0x00100 Read permission for owner.
0x00080 Write permission for owner.
0x00040 Execute permission for owner on a file. Or lookup
(search) permission for owner in directory.
0x00020 Read permission for group.
0x00010 Write permission for group.
0x00008 Execute permission for group on a file. Or lookup
(search) permission for group in directory.
0x00004 Read permission for others.
0x00002 Write permission for others.
0x00001 Execute permission for others on a file. Or lookup
(search) permission for others in directory.
post_op_attr
union post_op_attr switch (bool attributes_follow) {
case TRUE:
fattr3 attributes;
case FALSE:
void;
};
This structure is used for returning attributes in those operations that are not directly involved with manipulating attributes. One of the principles of this revision of the NFS protocol is to return the real value from the indicated operation and not an error from an incidental operation.
The post_op_attr structure was designed to allow the server to recover from errors encountered while getting attributes.
This appears to make returning attributes optional. However, server implementors are strongly encouraged to make best effort to return attributes whenever possible, even when returning an error.
wcc_attr
struct wcc_attr {
size3 size;
nfstime3 mtime;
nfstime3 ctime;
};
This is the subset of pre-operation attributes needed to better support the weak cache consistency semantics. Size is the file size in bytes of the object before the operation. Mtime is the time of last modification of the object before the operation.
Ctime is the time of last change to the attributes of the object before the operation. See discussion in wcc_attr on page 24.
The use of mtime by clients to detect changes to file system objects residing on a server is dependent on the granularity of the time base on the server.
pre_op_attr
union pre_op_attr switch (bool attributes_follow) {
case TRUE:
wcc_attr attributes;
case FALSE:
void;
};
wcc_data
struct wcc_data {
pre_op_attr before;
post_op_attr after;
};
When a client performs an operation that modifies the state of a file or directory on the server, it cannot immediately determine from the post-operation attributes whether the operation just performed was the only operation on the object since the last time the client received the attributes for the object. This is important, since if an intervening operation has changed the object, the client will need to invalidate any cached data for the object (except for the data that it just wrote).
To deal with this, the notion of weak cache consistency data or wcc_data is introduced. A wcc_data structure consists of certain key fields from the object attributes before the operation, together with the object attributes after the operation. This
information allows the client to manage its cache more accurately than in NFS version 2 protocol implementations. The term, weak cache consistency, emphasizes the fact that this mechanism does not provide the strict server-client consistency that a cache consistency protocol would provide.
In order to support the weak cache consistency model, the server will need to be able to get the pre-operation attributes of the object, perform the intended modify operation, and then get the post-operation attributes atomically. If there is a window for the object to get modified between the operation and either of the get attributes operations, then the client will not be able to determine whether it was the only entity to modify the object. Some information will have been lost, thus weakening the weak cache consistency guarantees.
post_op_fh3
union post_op_fh3 switch (bool handle_follows) {
case TRUE:
nfs_fh3 handle;
case FALSE:
void;
};
One of the principles of this revision of the NFS protocol is to return the real value from the indicated operation and not an error from an incidental operation. The post_op_fh3 structure was designed to allow the server to recover from errors encountered while constructing a file handle.
This is the structure used to return a file handle from the CREATE, MKDIR, SYMLINK, MKNOD, and READDIRPLUS requests. In each case, the client can get the file handle by issuing a LOOKUP request after a successful return from one of the listed operations. Returning the file handle is an optimization so that the client is not forced to immediately issue a LOOKUP request to get the file handle.
sattr3
enum time_how {
DONT_CHANGE = 0,
SET_TO_SERVER_TIME = 1,
SET_TO_CLIENT_TIME = 2
};
union set_mode3 switch (bool set_it) {
case TRUE:
mode3 mode;
default:
void;
};
union set_uid3 switch (bool set_it) {
case TRUE:
uid3 uid;
default:
void;
};
union set_gid3 switch (bool set_it) {
case TRUE:
gid3 gid;
default:
void;
};
union set_size3 switch (bool set_it) {
case TRUE:
size3 size;
default:
void;
};
union set_atime switch (time_how set_it) {
case SET_TO_CLIENT_TIME:
nfstime3 atime;
default:
void;
};
union set_mtime switch (time_how set_it) {
case SET_TO_CLIENT_TIME:
nfstime3 mtime;
default:
void;
};
struct sattr3 {
set_mode3 mode;
set_uid3 uid;
set_gid3 gid;
set_size3 size;
set_atime atime;
set_mtime mtime;
};
The sattr3 structure contains the file attributes that can be set from the client. The fields are the same as the similarly named fields in the fattr3 structure. In the NFS version 3 protocol, the settable attributes are described by a structure containing a set of discriminated unions. Each union indicates whether the corresponding attribute is to be updated, and if so, how.
There are two forms of discriminated unions used. In setting the mode, uid, gid, or size, the discriminated union is switched on a boolean, set_it; if it is TRUE, a value of the appropriate type is then encoded.
In setting the atime or mtime, the union is switched on an enumeration type, set_it. If set_it has the value DONT_CHANGE, the corresponding attribute is unchanged. If it has the value, SET_TO_SERVER_TIME, the corresponding attribute is set by the server to its local time; no data is provided by the client.
Finally, if set_it has the value, SET_TO_CLIENT_TIME, the attribute is set to the time passed by the client in an nfstime3 structure. (See FSINFO on page 86, which addresses the issue of time granularity).
diropargs3
struct diropargs3 {
nfs_fh3 dir;
filename3 name;
};
The diropargs3 structure is used in directory operations. The file handle, dir, identifies the directory in which to manipulate or access the file, name. See additional comments in File name component handling on page 101.
3. Server Procedures
The following sections define the RPC procedures that are supplied by an NFS version 3 protocol server. The RPC procedure number is given at the top of the page with the
name. The SYNOPSIS provides the name of the procedure, the list of the names of the arguments, the list of the names of the results, followed by the XDR argument declarations and results declarations. The information in the SYNOPSIS is specified in RPC Data Description Language as defined in [RFC1014]. The DESCRIPTION section tells what the procedure
is expected to do and how its arguments and results are used. The ERRORS section lists the errors returned for specific types of failures. These lists are not intended to be the definitive statement of all of the errors which can be returned by any specific procedure, but as a guide for the more common errors which may be returned. Client
implementations should be prepared to deal with unexpected errors coming from a server. The IMPLEMENTATION field gives information about how the procedure is expected to work and how it should be used by clients.
program NFS_PROGRAM {
version NFS_V3 {
void
NFSPROC3_NULL(void) = 0;
GETATTR3res
NFSPROC3_GETATTR(GETATTR3args) = 1;
SETATTR3res
NFSPROC3_SETATTR(SETATTR3args) = 2;
LOOKUP3res
NFSPROC3_LOOKUP(LOOKUP3args) = 3;
ACCESS3res
NFSPROC3_ACCESS(ACCESS3args) = 4;
READLINK3res
NFSPROC3_READLINK(READLINK3args) = 5;
READ3res
NFSPROC3_READ(READ3args) = 6;
WRITE3res
NFSPROC3_WRITE(WRITE3args) = 7;
CREATE3res
NFSPROC3_CREATE(CREATE3args) = 8;
MKDIR3res
NFSPROC3_MKDIR(MKDIR3args) = 9;
SYMLINK3res
NFSPROC3_SYMLINK(SYMLINK3args) = 10;
MKNOD3res
NFSPROC3_MKNOD(MKNOD3args) = 11;
REMOVE3res
NFSPROC3_REMOVE(REMOVE3args) = 12;
RMDIR3res
NFSPROC3_RMDIR(RMDIR3args) = 13;
RENAME3res
NFSPROC3_RENAME(RENAME3args) = 14;
LINK3res
NFSPROC3_LINK(LINK3args) = 15;
READDIR3res
NFSPROC3_READDIR(READDIR3args) = 16;
READDIRPLUS3res
NFSPROC3_READDIRPLUS(READDIRPLUS3args) = 17;
FSSTAT3res
NFSPROC3_FSSTAT(FSSTAT3args) = 18;
FSINFO3res
NFSPROC3_FSINFO(FSINFO3args) = 19;
PATHCONF3res
NFSPROC3_PATHCONF(PATHCONF3args) = 20;
COMMIT3res
NFSPROC3_COMMIT(COMMIT3args) = 21;
} = 3;
} = 100003;
Out of range (undefined) procedure numbers result in RPC
errors. Refer to [RFC1057] for more detail.
3.1 General comments on attributes and consistency data on failure
For those procedures that return either post_op_attr or wcc_data structures on failure, the discriminated union may contain the
pre-operation attributes of the object or object parent directory. This depends on the error encountered and may also
depend on the particular server implementation. Implementors are strongly encouraged to return as much attribute data as possible
upon failure, but client implementors need to be aware that their implementation must correctly handle the variant return
instance where no attributes or consistency data is returned.
3.2 General comments on filenames
The following comments apply to all NFS version 3 protocol procedures in which the client provides one or more filenames in
the arguments: LOOKUP, CREATE, MKDIR, SYMLINK, MKNOD, REMOVE, RMDIR, RENAME, and LINK.
1. The filename must not be null nor may it be the null
string. The server should return the error, NFS3ERR_ACCES, if
it receives such a filename. On some clients, the filename, ``''
or a null string, is assumed to be an alias for the current
directory. Clients which require this functionality should
implement it for themselves and not depend upon the server to
support such semantics.
2. A filename having the value of "." is assumed to be an
alias for the current directory. Clients which require this
functionality should implement it for themselves and not depend
upon the server to support such semantics. However, the server
should be able to handle such a filename correctly.
3. A filename having the value of ".." is assumed to be an
alias for the parent of the current directory, i.e. the
directory which contains the current directory. The server
should be prepared to handle this semantic, if it supports
directories, even if those directories do not contain UNIX-style
"." or ".." entries.
4. If the filename is longer than the maximum for the file
system (see PATHCONF on page 90, specifically name_max), the
result depends on the value of the PATHCONF flag, no_trunc. If
no_trunc is FALSE, the filename will be silently truncated to
name_max bytes. If no_trunc is TRUE and the filename exceeds the
server's file system maximum filename length, the operation will
fail with the error, NFS3ERR_NAMETOOLONG.
5. In general, there will be characters that a server will
not be able to handle as part of a filename. This set of
characters will vary from server to server and from
implementation to implementation. In most cases, it is the
server which will control the client's view of the file system.
If the server receives a filename containing characters that it
can not handle, the error, NFS3ERR_EACCES, should be returned.
Client implementations should be prepared to handle this side
affect of heterogeneity.
See also comments in File name component handling on page 101.
3.3.0 Procedure 0: NULL - Do nothing
SYNOPSIS
void NFSPROC3_NULL(void) = 0;
DESCRIPTION
Procedure NULL does not do any work. It is made available to
allow server response testing and timing.
IMPLEMENTATION
It is important that this procedure do no work at all so
that it can be used to measure the overhead of processing
a service request. By convention, the NULL procedure
should never require any authentication. A server may
choose to ignore this convention, in a more secure
implementation, where responding to the NULL procedure
call acknowledges the existence of a resource to an
unauthenticated client.
ERRORS
Since the NULL procedure takes no NFS version 3 protocol
arguments and returns no NFS version 3 protocol response,
it can not return an NFS version 3 protocol error.
However, it is possible that some server implementations
may return RPC errors based on security and authentication
requirements.
3.3.1 Procedure 1: GETATTR - Get file attributes
SYNOPSIS
GETATTR3res NFSPROC3_GETATTR(GETATTR3args) = 1;
struct GETATTR3args {
nfs_fh3 object;
};
struct GETATTR3resok {
fattr3 obj_attributes;
};
union GETATTR3res switch (nfsstat3 status) {
case NFS3_OK:
GETATTR3resok resok;
default:
void;
};
DESCRIPTION
Procedure GETATTR retrieves the attributes for a specified
file system object. The object is identified by the file
handle that the server returned as part of the response
from a LOOKUP, CREATE, MKDIR, SYMLINK, MKNOD, or
READDIRPLUS procedure (or from the MOUNT service,
described elsewhere). On entry, the arguments in
GETATTR3args are:
object
The file handle of an object whose attributes are to be
retrieved.
On successful return, GETATTR3res.status is NFS3_OK and
GETATTR3res.resok contains:
obj_attributes
The attributes for the object.
Otherwise, GETATTR3res.status contains the error on failure and
no other results are returned.
IMPLEMENTATION
The attributes of file system objects is a point of major
disagreement between different operating systems. Servers
should make a best attempt to support all of the
attributes in the fattr3 structure so that clients can
count on this as a common ground. Some mapping may be
required to map local attributes to those in the fattr3
structure.
Today, most client NFS version 3 protocol implementations
implement a time-bounded attribute caching scheme to
reduce over-the-wire attribute checks.
ERRORS
NFS3ERR_IO
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_SERVERFAULT
SEE ALSO
ACCESS.
3.3.2 Procedure 2: SETATTR - Set file attributes
SYNOPSIS
SETATTR3res NFSPROC3_SETATTR(SETATTR3args) = 2;
union sattrguard3 switch (bool check) {
case TRUE:
nfstime3 obj_ctime;
case FALSE:
void;
};
struct SETATTR3args {
nfs_fh3 object;
sattr3 new_attributes;
sattrguard3 guard;
};
struct SETATTR3resok {
wcc_data obj_wcc;
};
struct SETATTR3resfail {
wcc_data obj_wcc;
};
union SETATTR3res switch (nfsstat3 status) {
case NFS3_OK:
SETATTR3resok resok;
default:
SETATTR3resfail resfail;
};
DESCRIPTION
Procedure SETATTR changes one or more of the attributes of
a file system object on the server. The new attributes are
specified by a sattr3 structure. On entry, the arguments
in SETATTR3args are:
object
The file handle for the object.
new_attributes
A sattr3 structure containing booleans and
enumerations describing the attributes to be set and the new
values for those attributes.
guard
A sattrguard3 union:
check
TRUE if the server is to verify that guard.obj_ctime
matches the ctime for the object; FALSE otherwise.
A client may request that the server check that the object
is in an expected state before performing the SETATTR
operation. To do this, it sets the argument guard.check to
TRUE and the client passes a time value in guard.obj_ctime.
If guard.check is TRUE, the server must compare the value of
guard.obj_ctime to the current ctime of the object. If the
values are different, the server must preserve the object
attributes and must return a status of NFS3ERR_NOT_SYNC.
If guard.check is FALSE, the server will not perform this
check.
On successful return, SETATTR3res.status is NFS3_OK and
SETATTR3res.resok contains:
obj_wcc
A wcc_data structure containing the old and new
attributes for the object.
Otherwise, SETATTR3res.status contains the error on
failure and SETATTR3res.resfail contains the following:
obj_wcc
A wcc_data structure containing the old and new
attributes for the object.
IMPLEMENTATION
The guard.check mechanism allows the client to avoid
changing the attributes of an object on the basis of stale
attributes. It does not guarantee exactly-once semantics.
In particular, if a reply is lost and the server does not
detect the retransmission of the request, the procedure
can fail with the error, NFS3ERR_NOT_SYNC, even though the
attribute setting was previously performed successfully.
The client can attempt to recover from this error by
getting fresh attributes from the server and sending a new
SETATTR request using the new ctime. The client can
optionally check the attributes to avoid the second
SETATTR request if the new attributes show that the
attributes have already been set as desired (though it may
not have been the issuing client that set the
attributes).
The new_attributes.size field is used to request changes
to the size of a file. A value of 0 causes the file to be
truncated, a value less than the current size of the file
causes data from new size to the end of the file to be
discarded, and a size greater than the current size of the
file causes logically zeroed data bytes to be added to the
end of the file. Servers are free to implement this using
holes or actual zero data bytes. Clients should not make
any assumptions regarding a server's implementation of
this feature, beyond that the bytes returned will be
zeroed. Servers must support extending the file size via
SETATTR.
SETATTR is not guaranteed atomic. A failed SETATTR may
partially change a file's attributes.
Changing the size of a file with SETATTR indirectly
changes the mtime. A client must account for this as size
changes can result in data deletion.
If server and client times differ, programs that compare
client time to file times can break. A time maintenance
protocol should be used to limit client/server time skew.
In a heterogeneous environment, it is quite possible that
the server will not be able to support the full range of
SETATTR requests. The error, NFS3ERR_INVAL, may be
returned if the server can not store a uid or gid in its
own representation of uids or gids, respectively. If the
server can only support 32 bit offsets and sizes, a
SETATTR request to set the size of a file to larger than
can be represented in 32 bits will be rejected with this
same error.
ERRORS
NFS3ERR_PERM
NFS3ERR_IO
NFS3ERR_ACCES
NFS3ERR_INVAL
NFS3ERR_NOSPC
NFS3ERR_ROFS
NFS3ERR_DQUOT
NFS3ERR_NOT_SYNC
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_SERVERFAULT
SEE ALSO
CREATE, MKDIR, SYMLINK, and MKNOD.
3.3.3 Procedure 3: LOOKUP - Lookup filename
SYNOPSIS
LOOKUP3res NFSPROC3_LOOKUP(LOOKUP3args) = 3;
struct LOOKUP3args {
diropargs3 what;
};
struct LOOKUP3resok {
nfs_fh3 object;
post_op_attr obj_attributes;
post_op_attr dir_attributes;
};
struct LOOKUP3resfail {
post_op_attr dir_attributes;
};
union LOOKUP3res switch (nfsstat3 status) {
case NFS3_OK:
LOOKUP3resok resok;
default:
LOOKUP3resfail resfail;
};
DESCRIPTION
Procedure LOOKUP searches a directory for a specific name
and returns the file handle for the corresponding file
system object. On entry, the arguments in LOOKUP3args
are:
what
Object to look up:
dir
The file handle for the directory to search.
name
The filename to be searched for. Refer to General
comments on filenames on page 30.
On successful return, LOOKUP3res.status is NFS3_OK and
LOOKUP3res.resok contains:
object
The file handle of the object corresponding to
what.name.
obj_attributes
The attributes of the object corresponding to
what.name.
dir_attributes
The post-operation attributes of the directory,
what.dir.
Otherwise, LOOKUP3res.status contains the error on failure and
LOOKUP3res.resfail contains the following:
dir_attributes
The post-operation attributes for the directory,
what.dir.
IMPLEMENTATION
At first glance, in the case where what.name refers to a
mount point on the server, two different replies seem
possible. The server can return either the file handle for
the underlying directory that is mounted on or the file
handle of the root of the mounted directory. This
ambiguity is simply resolved. A server will not allow a
LOOKUP operation to cross a mountpoint to the root of a
different filesystem, even if the filesystem is exported.
This does not prevent a client from accessing a hierarchy
of filesystems exported by a server, but the client must
mount each of the filesystems individually so that the
mountpoint crossing takes place on the client. A given
server implementation may refine these rules given
capabilities or limitations particular to that
implementation. Refer to [X/OpenNFS] for a discussion on
exporting file systems.
Two filenames are distinguished, as in the NFS version 2
protocol. The name, ".", is an alias for the current
directory and the name, "..", is an alias for the parent
directory; that is, the directory that includes the
specified directory as a member. There is no facility for
dealing with a multiparented directory and the NFS
protocol assumes a hierarchical organization, organized as
a single-rooted tree.
Note that this procedure does not follow symbolic links.
The client is responsible for all parsing of filenames
including filenames that are modified by symbolic links
encountered during the lookup process.
ERRORS
NFS3ERR_IO
NFS3ERR_NOENT
NFS3ERR_ACCES
NFS3ERR_NOTDIR
NFS3ERR_NAMETOOLONG
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_SERVERFAULT
SEE ALSO
CREATE, MKDIR, SYMLINK, MKNOD, READDIRPLUS, and PATHCONF.
3.3.4 Procedure 4: ACCESS - Check Access Permission
SYNOPSIS
ACCESS3res NFSPROC3_ACCESS(ACCESS3args) = 4;
const ACCESS3_READ = 0x0001;
const ACCESS3_LOOKUP = 0x0002;
const ACCESS3_MODIFY = 0x0004;
const ACCESS3_EXTEND = 0x0008;
const ACCESS3_DELETE = 0x0010;
const ACCESS3_EXECUTE = 0x0020;
struct ACCESS3args {
nfs_fh3 object;
uint32 access;
};
struct ACCESS3resok {
post_op_attr obj_attributes;
uint32 access;
};
struct ACCESS3resfail {
post_op_attr obj_attributes;
};
union ACCESS3res switch (nfsstat3 status) {
case NFS3_OK:
ACCESS3resok resok;
default:
ACCESS3resfail resfail;
};
DESCRIPTION
Procedure ACCESS determines the access rights that a user,
as identified by the credentials in the request, has with
respect to a file system object. The client encodes the
set of permissions that are to be checked in a bit mask.
The server checks the permissions encoded in the bit mask.
A status of NFS3_OK is returned along with a bit mask
encoded with the permissions that the client is allowed.
The results of this procedure are necessarily advisory in
nature. That is, a return status of NFS3_OK and the
appropriate bit set in the bit mask does not imply that
such access will be allowed to the file system object in
the future, as access rights can be revoked by the server
at any time.
On entry, the arguments in ACCESS3args are:
object
The file handle for the file system object to which
access is to be checked.
access
A bit mask of access permissions to check.
The following access permissions may be requested:
ACCESS3_READ
Read data from file or read a directory.
ACCESS3_LOOKUP
Look up a name in a directory (no meaning for
non-directory objects).
ACCESS3_MODIFY
Rewrite existing file data or modify existing
directory entries.
ACCESS3_EXTEND
Write new data or add directory entries.
ACCESS3_DELETE
Delete an existing directory entry.
ACCESS3_EXECUTE
Execute file (no meaning for a directory).
On successful return, ACCESS3res.status is NFS3_OK. The
server should return a status of NFS3_OK if no errors
occurred that prevented the server from making the
required access checks. The results in ACCESS3res.resok
are:
obj_attributes
The post-operation attributes of object.
access
A bit mask of access permissions indicating access
rights for the authentication credentials provided with
the request.
Otherwise, ACCESS3res.status contains the error on failure
and ACCESS3res.resfail contains the following:
obj_attributes
The attributes of object - if access to attributes is
permitted.
IMPLEMENTATION
In general, it is not sufficient for the client to attempt
to deduce access permissions by inspecting the uid, gid,
and mode fields in the file attributes, since the server
may perform uid or gid mapping or enforce additional
access control restrictions. It is also possible that the
NFS version 3 protocol server may not be in the same ID
space as the NFS version 3 protocol client. In these cases
(and perhaps others), the NFS version 3 protocol client
can not reliably perform an access check with only current
file attributes.
In the NFS version 2 protocol, the only reliable way to
determine whether an operation was allowed was to try it
and see if it succeeded or failed. Using the ACCESS
procedure in the NFS version 3 protocol, the client can
ask the server to indicate whether or not one or more
classes of operations are permitted. The ACCESS operation
is provided to allow clients to check before doing a
series of operations. This is useful in operating systems
(such as UNIX) where permission checking is done only when
a file or directory is opened. This procedure is also
invoked by NFS client access procedure (called possibly
through access(2)). The intent is to make the behavior of
opening a remote file more consistent with the behavior of
opening a local file.
The information returned by the server in response to an
ACCESS call is not permanent. It was correct at the exact
time that the server performed the checks, but not
necessarily afterwards. The server can revoke access
permission at any time.
The NFS version 3 protocol client should use the effective
credentials of the user to build the authentication
information in the ACCESS request used to determine access
rights. It is the effective user and group credentials
that are used in subsequent read and write operations. See
the comments in Permission issues on page 98 for more
information on this topic.
Many implementations do not directly support the
ACCESS3_DELETE permission. Operating systems like UNIX
will ignore the ACCESS3_DELETE bit if set on an access
request on a non-directory object. In these systems,
delete permission on a file is determined by the access
permissions on the directory in which the file resides,
instead of being determined by the permissions of the file
itself. Thus, the bit mask returned for such a request
will have the ACCESS3_DELETE bit set to 0, indicating that
the client does not have this permission.
ERRORS
NFS3ERR_IO
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_SERVERFAULT
SEE ALSO
GETATTR.
3.3.5 Procedure 5: READLINK - Read from symbolic link
SYNOPSIS
READLINK3res NFSPROC3_READLINK(READLINK3args) = 5;
struct READLINK3args {
nfs_fh3 symlink;
};
struct READLINK3resok {
post_op_attr symlink_attributes;
nfspath3 data;
};
struct READLINK3resfail {
post_op_attr symlink_attributes;
};
union READLINK3res switch (nfsstat3 status) {
case NFS3_OK:
READLINK3resok resok;
default:
READLINK3resfail resfail;
};
DESCRIPTION
Procedure READLINK reads the data associated with a
symbolic link. The data is an ASCII string that is opaque
to the server. That is, whether created by the NFS
version 3 protocol software from a client or created
locally on the server, the data in a symbolic link is not
interpreted when created, but is simply stored. On entry,
the arguments in READLINK3args are:
symlink
The file handle for a symbolic link (file system object
of type NF3LNK).
On successful return, READLINK3res.status is NFS3_OK and
READLINK3res.resok contains:
data
The data associated with the symbolic link.
symlink_attributes
The post-operation attributes for the symbolic link.
Otherwise, READLINK3res.status contains the error on
failure and READLINK3res.resfail contains the following:
symlink_attributes
The post-operation attributes for the symbolic link.
IMPLEMENTATION
A symbolic link is nominally a pointer to another file.
The data is not necessarily interpreted by the server,
just stored in the file. It is possible for a client
implementation to store a path name that is not meaningful
to the server operating system in a symbolic link. A
READLINK operation returns the data to the client for
interpretation. If different implementations want to share
access to symbolic links, then they must agree on the
interpretation of the data in the symbolic link.
The READLINK operation is only allowed on objects of type,
NF3LNK. The server should return the error,
NFS3ERR_INVAL, if the object is not of type, NF3LNK.
(Note: The X/Open XNFS Specification for the NFS version 2
protocol defined the error status in this case as
NFSERR_NXIO. This is inconsistent with existing server
practice.)
ERRORS
NFS3ERR_IO
NFS3ERR_INVAL
NFS3ERR_ACCES
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_NOTSUPP
NFS3ERR_SERVERFAULT
SEE ALSO
READLINK, SYMLINK.
3.3.6 Procedure 6: READ - ファイルから読み込み
SYNOPSIS
READ3res NFSPROC3_READ(READ3args) = 6;
struct READ3args {
nfs_fh3 file;
offset3 offset;
count3 count;
};
struct READ3resok {
post_op_attr file_attributes;
count3 count;
bool eof;
opaque data<>;
};
struct READ3resfail {
post_op_attr file_attributes;
};
union READ3res switch (nfsstat3 status) {
case NFS3_OK:
READ3resok resok;
default:
READ3resfail resfail;
};
DESCRIPTION
Procedure READ reads data from a file. On entry, the arguments in READ3args are:
file
The file handle of the file from which data is to be read. This must identify a file system object of type, NF3REG.
offset
The position within the file at which the read is to begin. An offset of 0 means to read data starting at
the beginning of the file. If offset is greater than or equal to the size of the file, the status, NFS3_OK, is
returned with count set to 0 and eof set to TRUE, subject to access permissions checking.
count
The number of bytes of data that are to be read. If count is 0, the READ will succeed and return 0 bytes of
data, subject to access permissions checking. count must be less than or equal to the value of the rtmax
field in the FSINFO reply structure for the file system that contains file. If greater, the server may return
only rtmax bytes, resulting in a short read.
On successful return, READ3res.status is NFS3_OK and READ3res.resok contains:
file_attributes
The attributes of the file on completion of the read.
count
The number of bytes of data returned by the read.
eof
If the read ended at the end-of-file (formally, in a correctly formed READ request, if READ3args.offset plus
READ3resok.count is equal to the size of the file), eof is returned as TRUE; otherwise it is FALSE. A
successful READ of an empty file will always return eof as TRUE.
data
The counted data read from the file.
Otherwise, READ3res.status contains the error on failure and READ3res.resfail contains the following:
file_attributes
The post-operation attributes of the file.
IMPLEMENTATION
NFSバージョンでREADとWRITE操作に使用されるnfsdataタイプは、
要求または応答のデータ部分を定義する2プロトコルは、可変長の不透明なバイト配列に変更されました。
プロトコルによって許容される最大サイズは現在、XDRと基本的な輸送が許容するものによって制限されています。
NFSv3プロトコルによって課されたどんな人工の限界はありません。詳細については、FSINFO手順の説明を参照してください。
サーバはデータのcountバイト未満を返すことが可能です。サーバがFALSEに要求されたカウントとEOFセット未満を返した場合、クライアントは、発行する必要があります。
もう一つは残りのデータを取得するためにお読みください。サーバは、いくつかの状況下で要求されたより少ないデータを返す可能性があります。
ファイルが要求しているクライアントがケースであると信じているからファイルサイズを変更し、
サーバ自体におそらく別のクライアントまたはによって切り捨てられている可能性があります。
これは、クライアントが利用可能な実際のデータ量を減らすことができます。
それは、サーバが転送サイズをオフにバックアップし、読み出し要求リターンを減少させる可能性があります。
サーバ·リソースの枯渇も小さく、読み取りの戻り値を必要とする可能性があります。
いくつかのNFSバージョン2プロトコルクライアント実装は、EOFを示すように、短いリードの応答を解釈することにしました。
NFSv3プロトコルのEOFフラグの追加は、EOFを処理する正しい方法を提供します。
ファイル·システム·オブジェクト·タイプは、通常のファイルではありませんでした場合、
いくつかのNFSバージョン2プロトコルサーバ実装が間違ってNFSERR_ISDIRを返しました。
NFSバージョン3プロトコルの正しい戻り値はNFS3ERR_INVALです。
ERRORS
NFS3ERR_IO
NFS3ERR_NXIO
NFS3ERR_ACCES
NFS3ERR_INVAL
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_SERVERFAULT
SEE ALSO
READLINK.
3.3.7 Procedure 7: WRITE - Write to file
SYNOPSIS
WRITE3res NFSPROC3_WRITE(WRITE3args) = 7;
enum stable_how {
UNSTABLE = 0,
DATA_SYNC = 1,
FILE_SYNC = 2
};
struct WRITE3args {
nfs_fh3 file;
offset3 offset;
count3 count;
stable_how stable;
opaque data<>;
};
struct WRITE3resok {
wcc_data file_wcc;
count3 count;
stable_how committed;
writeverf3 verf;
};
struct WRITE3resfail {
wcc_data file_wcc;
};
union WRITE3res switch (nfsstat3 status) {
case NFS3_OK:
WRITE3resok resok;
default:
WRITE3resfail resfail;
};
DESCRIPTION
Procedure WRITE writes data to a file. On entry, the
arguments in WRITE3args are:
file
The file handle for the file to which data is to be
written. This must identify a file system object of
type, NF3REG.
offset
The position within the file at which the write is to
begin. An offset of 0 means to write data starting at
the beginning of the file.
count
The number of bytes of data to be written. If count is
0, the WRITE will succeed and return a count of 0,
barring errors due to permissions checking. The size of
data must be less than or equal to the value of the
wtmax field in the FSINFO reply structure for the file
system that contains file. If greater, the server may
write only wtmax bytes, resulting in a short write.
stable
If stable is FILE_SYNC, the server must commit the data written plus all file system metadata to stable storage
before returning results. This corresponds to the NFS version 2 protocol semantics. Any other behavior
constitutes a protocol violation. If stable is DATA_SYNC, then the server must commit all of the data
to stable storage and enough of the metadata to retrieve the data before returning. The server
implementor is free to implement DATA_SYNC in the same fashion as FILE_SYNC, but with a possible performance
drop. If stable is UNSTABLE, the server is free to commit any part of the data and the metadata to stable
storage, including all or none, before returning a reply to the client. There is no guarantee whether or
when any uncommitted data will subsequently be committed to stable storage. The only guarantees made
by the server are that it will not destroy any data without changing the value of verf and that it will not
commit the data and metadata at a level less than that requested by the client. See the discussion on COMMIT
on page 92 for more information on if and when data is committed to stable storage.
data
The data to be written to the file.
On successful return, WRITE3res.status is NFS3_OK and
WRITE3res.resok contains:
file_wcc
Weak cache consistency data for the file. For a client
that requires only the post-write file attributes,
these can be found in file_wcc.after.
count
The number of bytes of data written to the file. The
server may write fewer bytes than requested. If so, the
actual number of bytes written starting at location,
offset, is returned.
committed
The server should return an indication of the level of commitment of the data and metadata via committed. If
the server committed all data and metadata to stable storage, committed should be set to FILE_SYNC. If the
level of commitment was at least as strong as DATA_SYNC, then committed should be set to DATA_SYNC.
Otherwise, committed must be returned as UNSTABLE. If stable was FILE_SYNC, then committed must also be
FILE_SYNC: anything else constitutes a protocol violation. If stable was DATA_SYNC, then committed may
be FILE_SYNC or DATA_SYNC: anything else constitutes a protocol violation. If stable was UNSTABLE, then
committed may be either FILE_SYNC, DATA_SYNC, or UNSTABLE.
verf
This is a cookie that the client can use to determine
whether the server has changed state between a call to
WRITE and a subsequent call to either WRITE or COMMIT.
This cookie must be consistent during a single instance
of the NFS version 3 protocol service and must be
unique between instances of the NFS version 3 protocol
server, where uncommitted data may be lost.
Otherwise, WRITE3res.status contains the error on failure
and WRITE3res.resfail contains the following:
file_wcc
Weak cache consistency data for the file. For a client
that requires only the post-write file attributes,
these can be found in file_wcc.after. Even though the
write failed, full wcc_data is returned to allow the
client to determine whether the failed write resulted
in any change to the file.
If a client writes data to the server with the stable
argument set to UNSTABLE and the reply yields a committed
response of DATA_SYNC or UNSTABLE, the client will follow
up some time in the future with a COMMIT operation to
synchronize outstanding asynchronous data and metadata
with the server's stable storage, barring client error. It
is possible that due to client crash or other error that a
subsequent COMMIT will not be received by the server.
IMPLEMENTATION
NFSバージョンでREADとWRITE操作に使用されるnfsdataタイプは、要求または応答のデータ部分を定義する2プロトコルは、
可変長の不透明なバイト配列に変更されました。プロトコルによって許容される最大サイズは現在、
XDRと基本的な輸送が許容するものによって制限されています。
NFSv3プロトコルによって課されたどんな人工の限界はありません。詳細については、FSINFO手順の説明を参照してください。
サーバはデータのcountバイト未満を書き込みすることが可能です。データが全く書かれない限り、このケースでは、
サーバーがエラーを返すべきではありません。サーバはカウントバイト未満を書き込みした場合、
クライアントは残りのデータを書き込むために別のWRITEを発行する必要があります。
これは、ファイルにデータを書き込むという行為は、ファイルのmtimeが更新されるようになりますことを想定しています。
ファイルの内容が変更されない限り、ファイルのmtimeは変更すべきではありません。したがって、0に設定したカウントによるWRITE要求は、
更新するファイルのmtimeを引き起こすべきではありません。
NFSv3プロトコルでは、安全な非同期書き込みが導入されています。 COMMITが続く不安定版（unstable）に安定集合があるWRITEの組み合わせは、
NFSバージョン2プロトコル、同期はすべて安定したストレージへの書き込みはコミットする必要がで見つかった、
パフォーマンスのボトルネックに対処しています。
安定貯蔵の定義は歴史的に競合のポイントされています。安定したストレージは、次の予想されるプロパティは、
実装では、設計上の問題の解決に役立つ可能性があります。安定貯蔵は生き残る永続的なストレージです。
1。繰り返される停電。
2。ハードウェア障害（どんなボード、電源などの）。
3。リブートサイクルを含んでいて繰り返されるソフトウェアのクラッシュ、。
この定義は安定貯蔵モジュール自体の故障には対応していません。
クッキー、VERFは、クライアントはキャッシュされ、コミットされていないデータが失われる可能性があります
その上のNFSバージョン3プロトコルサーバの異なるインスタンスを検出できるように定義されています。
ほとんどのケースでは、verfはクライアントがサーバの再起動を検出することができます。
この情報は、クライアントが安全にサーバがキャッシュされたデータを失っているかどうかを判断できるようにする必要があります。
サーバーが予期せず失敗し、クライアントはそれが安定したストレージにキャッシュされたデータをフラッシュしていない可能性があります
前のWRITE要求（UNSTABLEに設定された安定した引数で、どのにコミット結果が同様にUNSTABLEとして返された行われます）
からのデータをコミットしている場合。回復の負担は、クライアント上にあり、クライアントはサーバにデータを再送する必要があります。
提案されVERFクッキーはサーバが起動された時刻、またはサーバーが最後に起動された時刻を
（もしあれば失われたバッファ内のリブートなしでサーバを再起動する）を使用することになります。
結果にコミットされたフィールドは、クライアントがより効果的なキャッシュを行うことができます。
サーバが安定したストレージへのすべてのWRITE要求をコミットしている場合、それは関係なく、
引数の安定したフィールドの値の、FILE_SYNCへのコミットセットを返す必要があります。
NVRAMアクセラレータを使用するサーバーは、このポリシーを実装するために選択することができます。
クライアントが既にサーバー上でコミットされたキャッシュされたデータを捨てることによってキャッシュの効果を高めるためにこれを使用することができます。
ユーザーのクォータを超過したとき、いくつかの実装がNFS3ERR_NOSPCの代わりにNFS3ERR_DQUOTを返す可能性があります。
ファイル·システム·オブジェクト·タイプは、通常のファイルではありませんでした場合、
いくつかのNFSバージョン2プロトコルサーバ実装が間違ってNFSERR_ISDIRを返しました。
NFSバージョン3プロトコルの正しい戻り値はNFS3ERR_INVALです。
ERRORS
NFS3ERR_IO
NFS3ERR_ACCES
NFS3ERR_FBIG
NFS3ERR_DQUOT
NFS3ERR_NOSPC
NFS3ERR_ROFS
NFS3ERR_INVAL
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_SERVERFAULT
SEE ALSO
COMMIT.
3.3.8 Procedure 8: CREATE - ファイル作成
SYNOPSIS
CREATE3res NFSPROC3_CREATE(CREATE3args) = 8;
enum createmode3 {
UNCHECKED = 0,
GUARDED = 1,
EXCLUSIVE = 2
};
union createhow3 switch (createmode3 mode) {
case UNCHECKED:
case GUARDED:
sattr3 obj_attributes;
case EXCLUSIVE:
createverf3 verf;
};
struct CREATE3args {
diropargs3 where;
createhow3 how;
};
struct CREATE3resok {
post_op_fh3 obj;
post_op_attr obj_attributes;
wcc_data dir_wcc;
};
struct CREATE3resfail {
wcc_data dir_wcc;
};
union CREATE3res switch (nfsstat3 status) {
case NFS3_OK:
CREATE3resok resok;
default:
CREATE3resfail resfail;
};
DESCRIPTION
Procedure CREATE creates a regular file. On entry, the arguments in CREATE3args are:
where
The location of the file to be created:
dir
The file handle for the directory in which the file is to be created.
name
The name that is to be associated with the created file. Refer to General comments on filenames on page 30.
When creating a regular file, there are three ways to create the file as defined by:
how
A discriminated union describing how the server is to
handle the file creation along with the appropriate
attributes:
mode
One of UNCHECKED, GUARDED, and EXCLUSIVE. UNCHECKED means that the file should be created without checking
for the existence of a duplicate file in the same directory. In this case, how.obj_attributes is a sattr3
describing the initial attributes for the file. GUARDED specifies that the server should check for the presence
of a duplicate file before performing the create and should fail the request with NFS3ERR_EXIST if a
duplicate file exists. If the file does not exist, the request is performed as described for UNCHECKED.
EXCLUSIVE specifies that the server is to follow exclusive creation semantics, using the verifier to
ensure exclusive creation of the target. No attributes may be provided in this case, since the server may use
the target file metadata to store the createverf3 verifier.
On successful return, CREATE3res.status is NFS3_OK and the
results in CREATE3res.resok are:
obj
The file handle of the newly created regular file.
obj_attributes
The attributes of the regular file just created.
dir_wcc
Weak cache consistency data for the directory,
where.dir. For a client that requires on the
post-CREATE directory attributes, these can be found in
dir_wcc.after.
Otherwise, CREATE3res.status contains the error on failure
and CREATE3res.resfail contains the following:
dir_wcc
Weak cache consistency data for the directory,
where.dir. For a client that requires only the
post-CREATE directory attributes, these can be found in
dir_wcc.after. Even though the CREATE failed, full
wcc_data is returned to allow the client to determine
whether the failing CREATE resulted in any change to
the directory.
IMPLEMENTATION
最初の属性構造内の特定のフィールドは、通常のファイルに加えて、
デバイスとFIFOの作成を示すためにオーバーロードされたNFSバージョン2プロトコルとは異なり、
この手順は、通常のファイルの作成をサポートしています。 MKNOD手順は、
デバイスとFIFOの作成を処理するNFSバージョン3プロトコルで導入されました。
実装では、過負荷のセマンティクスを作成する方法NFSバージョン3プロトコルには理由があるべきではありません。
NFSバージョン3プロトコルの一つの側面は、特に慎重な検討手順を保証します。
CREATE機構は、通常のファイルの信頼性のある排他的な作成をサポートするために導入されています。
how.modeがexclusiveの場合機構が場に出る。このケースでは、how.verfは、
合理的に一意であることが予想されるベリファイアが含まれています。
クライアント識別子、恐らくクライアントネットワークアドレス、
およびクライアントによって生成される一意の番号の組み合わせは、
おそらくRPCトランザクション識別子は、適切であるかもしれません。
ファイルが存在しない場合、サーバーはファイルを作成し、安定したストレージ内のベリファイアを格納します。
任意のファイルの属性を格納するためのメカニズムを提供していないファイルシステムの場合、
サーバーはベリファイアを格納するファイルのメタデータの1つまたは複数の要素を使用することができます。
検証は、要求の再送信に誤ったエラーを防ぐために、安定したストレージに格納する必要があります。
排他的なセマンティクスはアプリケーションにとって重要であるので、
それは排他的な作成が実行されていることを想定しています。ため予想使用量の、排他的なCREATEは、
ベリファイアを格納するための通常揮発性の重複要求キャッシュだけに頼ることはありません。
揮発性記憶装置内の重複要求キャッシュは、クラッシュを生き延びるないし、
実際に障害のウィンドウを開く、長いネットワークパーティションにフラッシュすることがあります。
UNIXローカルファイルシステム環境では、作成時にベリファイアの期待保管場所は、
ファイルのメタデータ（タイムスタンプ）です。この理由のために、排他的ファイルを作成、
サーバーが検証を保存するためにどこにもないであろうため、初期の属性を含めることはできません。
サーバーは、可能性のため安定したストレージに検証をコミットするための要件
これらの排他的な作成のセマンティクスをサポートできない場合は、
NFS3ERR_NOTSUPP、エラーでCREATE要求を失敗する必要があります。
ファイルが既に存在する場合、排他的なCREATE要求時に、サーバはファイルのベリファイアを再構築し、
要求の検証とそれを比較します。それらが一致すれば、サーバは成功として要求を扱います。
要求は、応答が失われ、サーバーの重複要求キャッシュメカニズムが検出されなかったこととなる以前では、
成功したリクエストの重複であると推定される。検証が一致しない場合、要求はステータス、NFS3ERR_EXISTで拒否されます。
クライアントが成功した排他的な作成を実行した後は、正しいファイル属性を設定するためにSETATTRを発行する必要があります。
それがそうするまで、サーバの実装では、ベリファイアを格納するために過負荷ファイルのメタデータに必要になる場合がありますので、
それは、ファイルの属性のいずれかに頼るべきではありません。
ガード属性の使用は必ず1回のセマンティクスを提供していません。
応答が失われ、サーバはリクエストの再送を検出しない場合、特に、プロシージャは作成が正常に実行されているにもかかわらず、
NFS3ERR_EXISTで失敗することができます。
30ページのファイル名の一般コメントを参照してください。
ERRORS
NFS3ERR_IO
NFS3ERR_ACCES
NFS3ERR_EXIST
NFS3ERR_NOTDIR
NFS3ERR_NOSPC
NFS3ERR_ROFS
NFS3ERR_NAMETOOLONG
NFS3ERR_DQUOT
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_NOTSUPP
NFS3ERR_SERVERFAULT
SEE ALSO
MKDIR, SYMLINK, MKNOD, and PATHCONF.
3.3.9 Procedure 9: MKDIR - Create a directory
SYNOPSIS
MKDIR3res NFSPROC3_MKDIR(MKDIR3args) = 9;
struct MKDIR3args {
diropargs3 where;
sattr3 attributes;
};
struct MKDIR3resok {
post_op_fh3 obj;
post_op_attr obj_attributes;
wcc_data dir_wcc;
};
struct MKDIR3resfail {
wcc_data dir_wcc;
};
union MKDIR3res switch (nfsstat3 status) {
case NFS3_OK:
MKDIR3resok resok;
default:
MKDIR3resfail resfail;
};
DESCRIPTION
Procedure MKDIR creates a new subdirectory. On entry, the
arguments in MKDIR3args are:
where
The location of the subdirectory to be created:
dir
The file handle for the directory in which the
subdirectory is to be created.
name
The name that is to be associated with the created
subdirectory. Refer to General comments on filenames
on page 30.
attributes
The initial attributes for the subdirectory.
On successful return, MKDIR3res.status is NFS3_OK and the
results in MKDIR3res.resok are:
obj
The file handle for the newly created directory.
obj_attributes
The attributes for the newly created subdirectory.
dir_wcc
Weak cache consistency data for the directory,
where.dir. For a client that requires only the
post-MKDIR directory attributes, these can be found in
dir_wcc.after.
Otherwise, MKDIR3res.status contains the error on failure
and MKDIR3res.resfail contains the following:
dir_wcc
Weak cache consistency data for the directory,
where.dir. For a client that requires only the
post-MKDIR directory attributes, these can be found in
dir_wcc.after. Even though the MKDIR failed, full
wcc_data is returned to allow the client to determine
whether the failing MKDIR resulted in any change to the
directory.
IMPLEMENTATION
Many server implementations will not allow the filenames,
"." or "..", to be used as targets in a MKDIR operation.
In this case, the server should return NFS3ERR_EXIST.
Refer to General comments on filenames on page 30.
ERRORS
NFS3ERR_IO
NFS3ERR_ACCES
NFS3ERR_EXIST
NFS3ERR_NOTDIR
NFS3ERR_NOSPC
NFS3ERR_ROFS
NFS3ERR_NAMETOOLONG
NFS3ERR_DQUOT
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_NOTSUPP
NFS3ERR_SERVERFAULT
SEE ALSO
CREATE, SYMLINK, MKNOD, and PATHCONF.
3.3.10 Procedure 10: SYMLINK - Create a symbolic link
SYNOPSIS
SYMLINK3res NFSPROC3_SYMLINK(SYMLINK3args) = 10;
struct symlinkdata3 {
sattr3 symlink_attributes;
nfspath3 symlink_data;
};
struct SYMLINK3args {
diropargs3 where;
symlinkdata3 symlink;
};
struct SYMLINK3resok {
post_op_fh3 obj;
post_op_attr obj_attributes;
wcc_data dir_wcc;
};
struct SYMLINK3resfail {
wcc_data dir_wcc;
};
union SYMLINK3res switch (nfsstat3 status) {
case NFS3_OK:
SYMLINK3resok resok;
default:
SYMLINK3resfail resfail;
};
DESCRIPTION
Procedure SYMLINK creates a new symbolic link. On entry,
the arguments in SYMLINK3args are:
where
The location of the symbolic link to be created:
dir
The file handle for the directory in which the
symbolic link is to be created.
name
The name that is to be associated with the created
symbolic link. Refer to General comments on
filenames on page 30.
symlink
The symbolic link to create:
symlink_attributes
The initial attributes for the symbolic link.
symlink_data
The string containing the symbolic link data.
On successful return, SYMLINK3res.status is NFS3_OK and
SYMLINK3res.resok contains:
obj
The file handle for the newly created symbolic link.
obj_attributes
The attributes for the newly created symbolic link.
dir_wcc
Weak cache consistency data for the directory,
where.dir. For a client that requires only the
post-SYMLINK directory attributes, these can be found
in dir_wcc.after.
Otherwise, SYMLINK3res.status contains the error on
failure and SYMLINK3res.resfail contains the following:
dir_wcc
Weak cache consistency data for the directory,
where.dir. For a client that requires only the
post-SYMLINK directory attributes, these can be found
in dir_wcc.after. Even though the SYMLINK failed, full
wcc_data is returned to allow the client to determine
whether the failing SYMLINK changed the directory.
IMPLEMENTATION
Refer to General comments on filenames on page 30.
For symbolic links, the actual file system node and its
contents are expected to be created in a single atomic
operation. That is, once the symbolic link is visible,
there must not be a window where a READLINK would fail or
return incorrect data.
ERRORS
NFS3ERR_IO
NFS3ERR_ACCES
NFS3ERR_EXIST
NFS3ERR_NOTDIR
NFS3ERR_NOSPC
NFS3ERR_ROFS
NFS3ERR_NAMETOOLONG
NFS3ERR_DQUOT
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_NOTSUPP
NFS3ERR_SERVERFAULT
SEE ALSO
READLINK, CREATE, MKDIR, MKNOD, FSINFO, and PATHCONF.
3.3.11 Procedure 11: MKNOD - Create a special device
SYNOPSIS
MKNOD3res NFSPROC3_MKNOD(MKNOD3args) = 11;
struct devicedata3 {
sattr3 dev_attributes;
specdata3 spec;
};
union mknoddata3 switch (ftype3 type) {
case NF3CHR:
case NF3BLK:
devicedata3 device;
case NF3SOCK:
case NF3FIFO:
sattr3 pipe_attributes;
default:
void;
};
struct MKNOD3args {
diropargs3 where;
mknoddata3 what;
};
struct MKNOD3resok {
post_op_fh3 obj;
post_op_attr obj_attributes;
wcc_data dir_wcc;
};
struct MKNOD3resfail {
wcc_data dir_wcc;
};
union MKNOD3res switch (nfsstat3 status) {
case NFS3_OK:
MKNOD3resok resok;
default:
MKNOD3resfail resfail;
};
DESCRIPTION
Procedure MKNOD creates a new special file of the type,
what.type. Special files can be device files or named
pipes. On entry, the arguments in MKNOD3args are:
where
The location of the special file to be created:
dir
The file handle for the directory in which the
special file is to be created.
name
The name that is to be associated with the created
special file. Refer to General comments on filenames
on page 30.
what
A discriminated union identifying the type of the
special file to be created along with the data and
attributes appropriate to the type of the special
file:
type
The type of the object to be created.
When creating a character special file (what.type is
NF3CHR) or a block special file (what.type is NF3BLK),
what includes:
device
A structure devicedata3 with the following components:
dev_attributes
The initial attributes for the special file.
spec
The major number stored in device.spec.specdata1 and
the minor number stored in device.spec.specdata2.
When creating a socket (what.type is NF3SOCK) or a FIFO
(what.type is NF3FIFO), what includes:
pipe_attributes
The initial attributes for the special file.
On successful return, MKNOD3res.status is NFS3_OK and
MKNOD3res.resok contains:
obj
The file handle for the newly created special file.
obj_attributes
The attributes for the newly created special file.
dir_wcc
Weak cache consistency data for the directory,
where.dir. For a client that requires only the
post-MKNOD directory attributes, these can be found in
dir_wcc.after.
Otherwise, MKNOD3res.status contains the error on failure
and MKNOD3res.resfail contains the following:
dir_wcc
Weak cache consistency data for the directory,
where.dir. For a client that requires only the
post-MKNOD directory attributes, these can be found in
dir_wcc.after. Even though the MKNOD failed, full
wcc_data is returned to allow the client to determine
whether the failing MKNOD changed the directory.
IMPLEMENTATION
Refer to General comments on filenames on page 30.
Without explicit support for special file type creation in
the NFS version 2 protocol, fields in the CREATE arguments
were overloaded to indicate creation of certain types of
objects. This overloading is not necessary in the NFS
version 3 protocol.
If the server does not support any of the defined types,
the error, NFS3ERR_NOTSUPP, should be returned. Otherwise,
if the server does not support the target type or the
target type is illegal, the error, NFS3ERR_BADTYPE, should
be returned. Note that NF3REG, NF3DIR, and NF3LNK are
illegal types for MKNOD. The procedures, CREATE, MKDIR,
and SYMLINK should be used to create these file types,
respectively, instead of MKNOD.
ERRORS
NFS3ERR_IO
NFS3ERR_ACCES
NFS3ERR_EXIST
NFS3ERR_NOTDIR
NFS3ERR_NOSPC
NFS3ERR_ROFS
NFS3ERR_NAMETOOLONG
NFS3ERR_DQUOT
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_NOTSUPP
NFS3ERR_SERVERFAULT
NFS3ERR_BADTYPE
SEE ALSO
CREATE, MKDIR, SYMLINK, and PATHCONF.
3.3.12 Procedure 12: REMOVE - Remove a File
SYNOPSIS
REMOVE3res NFSPROC3_REMOVE(REMOVE3args) = 12;
struct REMOVE3args {
diropargs3 object;
};
struct REMOVE3resok {
wcc_data dir_wcc;
};
struct REMOVE3resfail {
wcc_data dir_wcc;
};
union REMOVE3res switch (nfsstat3 status) {
case NFS3_OK:
REMOVE3resok resok;
default:
REMOVE3resfail resfail;
};
DESCRIPTION
Procedure REMOVE removes (deletes) an entry from a
directory. If the entry in the directory was the last
reference to the corresponding file system object, the
object may be destroyed. On entry, the arguments in
REMOVE3args are:
object
A diropargs3 structure identifying the entry to be
removed:
dir
The file handle for the directory from which the entry
is to be removed.
name
The name of the entry to be removed. Refer to General
comments on filenames on page 30.
On successful return, REMOVE3res.status is NFS3_OK and
REMOVE3res.resok contains:
dir_wcc
Weak cache consistency data for the directory,
object.dir. For a client that requires only the
post-REMOVE directory attributes, these can be found in
dir_wcc.after.
Otherwise, REMOVE3res.status contains the error on failure
and REMOVE3res.resfail contains the following:
dir_wcc
Weak cache consistency data for the directory,
object.dir. For a client that requires only the
post-REMOVE directory attributes, these can be found in
dir_wcc.after. Even though the REMOVE failed, full
wcc_data is returned to allow the client to determine
whether the failing REMOVE changed the directory.
IMPLEMENTATION
In general, REMOVE is intended to remove non-directory
file objects and RMDIR is to be used to remove
directories. However, REMOVE can be used to remove
directories, subject to restrictions imposed by either the
client or server interfaces. This had been a source of
confusion in the NFS version 2 protocol.
The concept of last reference is server specific. However,
if the nlink field in the previous attributes of the
object had the value 1, the client should not rely on
referring to the object via a file handle. Likewise, the
client should not rely on the resources (disk space,
directory entry, and so on.) formerly associated with the
object becoming immediately available. Thus, if a client
needs to be able to continue to access a file after using
REMOVE to remove it, the client should take steps to make
sure that the file will still be accessible. The usual
mechanism used is to use RENAME to rename the file from
its old name to a new hidden name.
Refer to General comments on filenames on page 30.
ERRORS
NFS3ERR_NOENT
NFS3ERR_IO
NFS3ERR_ACCES
NFS3ERR_NOTDIR
NFS3ERR_NAMETOOLONG
NFS3ERR_ROFS
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_SERVERFAULT
SEE ALSO
RMDIR and RENAME.
3.3.13 Procedure 13: RMDIR - Remove a Directory
SYNOPSIS
RMDIR3res NFSPROC3_RMDIR(RMDIR3args) = 13;
struct RMDIR3args {
diropargs3 object;
};
struct RMDIR3resok {
wcc_data dir_wcc;
};
struct RMDIR3resfail {
wcc_data dir_wcc;
};
union RMDIR3res switch (nfsstat3 status) {
case NFS3_OK:
RMDIR3resok resok;
default:
RMDIR3resfail resfail;
};
DESCRIPTION
Procedure RMDIR removes (deletes) a subdirectory from a
directory. If the directory entry of the subdirectory is
the last reference to the subdirectory, the subdirectory
may be destroyed. On entry, the arguments in RMDIR3args
are:
object
A diropargs3 structure identifying the directory entry
to be removed:
dir
The file handle for the directory from which the
subdirectory is to be removed.
name
The name of the subdirectory to be removed. Refer to
General comments on filenames on page 30.
On successful return, RMDIR3res.status is NFS3_OK and
RMDIR3res.resok contains:
dir_wcc
Weak cache consistency data for the directory,
object.dir. For a client that requires only the
post-RMDIR directory attributes, these can be found in
dir_wcc.after.
Otherwise, RMDIR3res.status contains the error on failure
and RMDIR3res.resfail contains the following:
dir_wcc
Weak cache consistency data for the directory,
object.dir. For a client that requires only the
post-RMDIR directory attributes, these can be found in
dir_wcc.after. Note that even though the RMDIR failed,
full wcc_data is returned to allow the client to
determine whether the failing RMDIR changed the
directory.
IMPLEMENTATION
Note that on some servers, removal of a non-empty
directory is disallowed.
On some servers, the filename, ".", is illegal. These
servers will return the error, NFS3ERR_INVAL. On some
servers, the filename, "..", is illegal. These servers
will return the error, NFS3ERR_EXIST. This would seem
inconsistent, but allows these servers to comply with
their own specific interface definitions. Clients should
be prepared to handle both cases.
The client should not rely on the resources (disk space,
directory entry, and so on.) formerly associated with the
directory becoming immediately available.
ERRORS
NFS3ERR_NOENT
NFS3ERR_IO
NFS3ERR_ACCES
NFS3ERR_INVAL
NFS3ERR_EXIST
NFS3ERR_NOTDIR
NFS3ERR_NAMETOOLONG
NFS3ERR_ROFS
NFS3ERR_NOTEMPTY
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_NOTSUPP
NFS3ERR_SERVERFAULT
SEE ALSO
REMOVE.
3.3.14 Procedure 14: RENAME - Rename a File or Directory
SYNOPSIS
RENAME3res NFSPROC3_RENAME(RENAME3args) = 14;
struct RENAME3args {
diropargs3 from;
diropargs3 to;
};
struct RENAME3resok {
wcc_data fromdir_wcc;
wcc_data todir_wcc;
};
struct RENAME3resfail {
wcc_data fromdir_wcc;
wcc_data todir_wcc;
};
union RENAME3res switch (nfsstat3 status) {
case NFS3_OK:
RENAME3resok resok;
default:
RENAME3resfail resfail;
};
DESCRIPTION
Procedure RENAME renames the file identified by from.name
in the directory, from.dir, to to.name in the di- rectory,
to.dir. The operation is required to be atomic to the
client. To.dir and from.dir must reside on the same file
system and server. On entry, the arguments in RENAME3args
are:
from
A diropargs3 structure identifying the source (the file
system object to be re-named):
from.dir
The file handle for the directory from which the
entry is to be renamed.
from.name
The name of the entry that identifies the object to
be renamed. Refer to General comments on filenames
on page 30.
to
A diropargs3 structure identifying the target (the new
name of the object):
to.dir
The file handle for the directory to which the
object is to be renamed.
to.name
The new name for the object. Refer to General
comments on filenames on page 30.
If the directory, to.dir, already contains an entry with
the name, to.name, the source object must be compatible
with the target: either both are non-directories or both
are directories and the target must be empty. If
compatible, the existing target is removed before the
rename occurs. If they are not compatible or if the target
is a directory but not empty, the server should return the
error, NFS3ERR_EXIST.
On successful return, RENAME3res.status is NFS3_OK and
RENAME3res.resok contains:
fromdir_wcc
Weak cache consistency data for the directory,
from.dir.
todir_wcc
Weak cache consistency data for the directory, to.dir.
Otherwise, RENAME3res.status contains the error on failure
and RENAME3res.resfail contains the following:
fromdir_wcc
Weak cache consistency data for the directory,
from.dir.
todir_wcc
Weak cache consistency data for the directory, to.dir.
IMPLEMENTATION
The RENAME operation must be atomic to the client. The
message "to.dir and from.dir must reside on the same file
system on the server, [or the operation will fail]" means
that the fsid fields in the attributes for the directories
are the same. If they reside on different file systems,
the error, NFS3ERR_XDEV, is returned. Even though the
operation is atomic, the status, NFS3ERR_MLINK, may be
returned if the server used a "unlink/link/unlink"
sequence internally.
A file handle may or may not become stale on a rename.
However, server implementors are strongly encouraged to
attempt to keep file handles from becoming stale in this
fashion.
On some servers, the filenames, "." and "..", are illegal
as either from.name or to.name. In addition, neither
from.name nor to.name can be an alias for from.dir. These
servers will return the error, NFS3ERR_INVAL, in these
cases.
If from and to both refer to the same file (they might
be hard links of each other), then RENAME should perform
no action and return NFS3_OK.
Refer to General comments on filenames on page 30.
ERRORS
NFS3ERR_NOENT
NFS3ERR_IO
NFS3ERR_ACCES
NFS3ERR_EXIST
NFS3ERR_XDEV
NFS3ERR_NOTDIR
NFS3ERR_ISDIR
NFS3ERR_INVAL
NFS3ERR_NOSPC
NFS3ERR_ROFS
NFS3ERR_MLINK
NFS3ERR_NAMETOOLONG
NFS3ERR_NOTEMPTY
NFS3ERR_DQUOT
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_NOTSUPP
NFS3ERR_SERVERFAULT
SEE ALSO
REMOVE and LINK.
3.3.15 Procedure 15: LINK - Create Link to an object
SYNOPSIS
LINK3res NFSPROC3_LINK(LINK3args) = 15;
struct LINK3args {
nfs_fh3 file;
diropargs3 link;
};
struct LINK3resok {
post_op_attr file_attributes;
wcc_data linkdir_wcc;
};
struct LINK3resfail {
post_op_attr file_attributes;
wcc_data linkdir_wcc;
};
union LINK3res switch (nfsstat3 status) {
case NFS3_OK:
LINK3resok resok;
default:
LINK3resfail resfail;
};
DESCRIPTION
Procedure LINK creates a hard link from file to link.name,
in the directory, link.dir. file and link.dir must reside
on the same file system and server. On entry, the
arguments in LINK3args are:
file
The file handle for the existing file system object.
link
The location of the link to be created:
link.dir
The file handle for the directory in which the link
is to be created.
link.name
The name that is to be associated with the created
link. Refer to General comments on filenames on page
17.
On successful return, LINK3res.status is NFS3_OK and
LINK3res.resok contains:
file_attributes
The post-operation attributes of the file system object
identified by file.
linkdir_wcc
Weak cache consistency data for the directory,
link.dir.
Otherwise, LINK3res.status contains the error on failure
and LINK3res.resfail contains the following:
file_attributes
The post-operation attributes of the file system object
identified by file.
linkdir_wcc
Weak cache consistency data for the directory,
link.dir.
IMPLEMENTATION
Changes to any property of the hard-linked files are
reflected in all of the linked files. When a hard link is
made to a file, the attributes for the file should have a
value for nlink that is one greater than the value before
the LINK.
The comments under RENAME regarding object and target
residing on the same file system apply here as well. The
comments regarding the target name applies as well. Refer
to General comments on filenames on page 30.
ERRORS
NFS3ERR_IO
NFS3ERR_ACCES
NFS3ERR_EXIST
NFS3ERR_XDEV
NFS3ERR_NOTDIR
NFS3ERR_INVAL
NFS3ERR_NOSPC
NFS3ERR_ROFS
NFS3ERR_MLINK
NFS3ERR_NAMETOOLONG
NFS3ERR_DQUOT
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_NOTSUPP
NFS3ERR_SERVERFAULT
SEE ALSO
SYMLINK, RENAME and FSINFO.
3.3.16 Procedure 16: READDIR - Read From Directory
SYNOPSIS
READDIR3res NFSPROC3_READDIR(READDIR3args) = 16;
struct READDIR3args {
nfs_fh3 dir;
cookie3 cookie;
cookieverf3 cookieverf;
count3 count;
};
struct entry3 {
fileid3 fileid;
filename3 name;
cookie3 cookie;
entry3 *nextentry;
};
struct dirlist3 {
entry3 *entries;
bool eof;
};
struct READDIR3resok {
post_op_attr dir_attributes;
cookieverf3 cookieverf;
dirlist3 reply;
};
struct READDIR3resfail {
post_op_attr dir_attributes;
};
union READDIR3res switch (nfsstat3 status) {
case NFS3_OK:
READDIR3resok resok;
default:
READDIR3resfail resfail;
};
DESCRIPTION
Procedure READDIR retrieves a variable number of entries,
in sequence, from a directory and returns the name and
file identifier for each, with information to allow the
client to request additional directory entries in a
subsequent READDIR request. On entry, the arguments in
READDIR3args are:
dir
The file handle for the directory to be read.
cookie
This should be set to 0 in the first request to read
the directory. On subsequent requests, it should be a
cookie as returned by the server.
cookieverf
This should be set to 0 in the first request to read
the directory. On subsequent requests, it should be a
cookieverf as returned by the server. The cookieverf
must match that returned by the READDIR in which the
cookie was acquired.
count
The maximum size of the READDIR3resok structure, in
bytes. The size must include all XDR overhead. The
server is free to return less than count bytes of
data.
On successful return, READDIR3res.status is NFS3_OK and
READDIR3res.resok contains:
dir_attributes
The attributes of the directory, dir.
cookieverf
The cookie verifier.
reply
The directory list:
entries
Zero or more directory (entry3) entries.
eof
TRUE if the last member of reply.entries is the last
entry in the directory or the list reply.entries is
empty and the cookie corresponded to the end of the
directory. If FALSE, there may be more entries to
read.
Otherwise, READDIR3res.status contains the error on
failure and READDIR3res.resfail contains the following:
dir_attributes
The attributes of the directory, dir.
IMPLEMENTATION
In the NFS version 2 protocol, each directory entry
returned included a cookie identifying a point in the
directory. By including this cookie in a subsequent
READDIR, the client could resume the directory read at any
point in the directory. One problem with this scheme was
that there was no easy way for a server to verify that a
cookie was valid. If two READDIRs were separated by one or
more operations that changed the directory in some way
(for example, reordering or compressing it), it was
possible that the second READDIR could miss entries, or
process entries more than once. If the cookie was no
longer usable, for example, pointing into the middle of a
directory entry, the server would have to either round the
cookie down to the cookie of the previous entry or round
it up to the cookie of the next entry in the directory.
Either way would possibly lead to incorrect results and
the client would be unaware that any problem existed.
In the NFS version 3 protocol, each READDIR request
includes both a cookie and a cookie verifier. For the
first call, both are set to 0. The response includes a
new cookie verifier, with a cookie per entry. For
subsequent READDIRs, the client must present both the
cookie and the corresponding cookie verifier. If the
server detects that the cookie is no longer valid, the
server will reject the READDIR request with the status,
NFS3ERR_BAD_COOKIE. The client should be careful to
avoid holding directory entry cookies across operations
that modify the directory contents, such as REMOVE and
CREATE.
One implementation of the cookie-verifier mechanism might
be for the server to use the modification time of the
directory. This might be overly restrictive, however. A
better approach would be to record the time of the last
directory modification that changed the directory
organization in a way that would make it impossible to
reliably interpret a cookie. Servers in which directory
cookies are always valid are free to use zero as the
verifier always.
The server may return fewer than count bytes of
XDR-encoded entries. The count specified by the client in
the request should be greater than or equal to FSINFO
dtpref.
Since UNIX clients give a special meaning to the fileid
value zero, UNIX clients should be careful to map zero
fileid values to some other value and servers should try
to avoid sending a zero fileid.
ERRORS
NFS3ERR_IO
NFS3ERR_ACCES
NFS3ERR_NOTDIR
NFS3ERR_BAD_COOKIE
NFS3ERR_TOOSMALL
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_SERVERFAULT
SEE ALSO
READDIRPLUS and FSINFO.
3.3.17 Procedure 17: READDIRPLUS - Extended read from directory
SYNOPSIS
READDIRPLUS3res NFSPROC3_READDIRPLUS(READDIRPLUS3args) = 17;
struct READDIRPLUS3args {
nfs_fh3 dir;
cookie3 cookie;
cookieverf3 cookieverf;
count3 dircount;
count3 maxcount;
};
struct entryplus3 {
fileid3 fileid;
filename3 name;
cookie3 cookie;
post_op_attr name_attributes;
post_op_fh3 name_handle;
entryplus3 *nextentry;
};
struct dirlistplus3 {
entryplus3 *entries;
bool eof;
};
struct READDIRPLUS3resok {
post_op_attr dir_attributes;
cookieverf3 cookieverf;
dirlistplus3 reply;
};
struct READDIRPLUS3resfail {
post_op_attr dir_attributes;
};
union READDIRPLUS3res switch (nfsstat3 status) {
case NFS3_OK:
READDIRPLUS3resok resok;
default:
READDIRPLUS3resfail resfail;
};
DESCRIPTION
Procedure READDIRPLUS retrieves a variable number of
entries from a file system directory and returns complete
information about each along with information to allow the
client to request additional directory entries in a
subsequent READDIRPLUS. READDIRPLUS differs from READDIR
only in the amount of information returned for each
entry. In READDIR, each entry returns the filename and
the fileid. In READDIRPLUS, each entry returns the name,
the fileid, attributes (including the fileid), and file
handle. On entry, the arguments in READDIRPLUS3args are:
dir
The file handle for the directory to be read.
cookie
This should be set to 0 on the first request to read a
directory. On subsequent requests, it should be a
cookie as returned by the server.
cookieverf
This should be set to 0 on the first request to read a
directory. On subsequent requests, it should be a
cookieverf as returned by the server. The cookieverf
must match that returned by the READDIRPLUS call in
which the cookie was acquired.
dircount
The maximum number of bytes of directory information
returned. This number should not include the size of
the attributes and file handle portions of the result.
maxcount
The maximum size of the READDIRPLUS3resok structure, in
bytes. The size must include all XDR overhead. The
server is free to return fewer than maxcount bytes of
data.
On successful return, READDIRPLUS3res.status is NFS3_OK
and READDIRPLUS3res.resok contains:
dir_attributes
The attributes of the directory, dir.
cookieverf
The cookie verifier.
reply
The directory list:
entries
Zero or more directory (entryplus3) entries.
eof
TRUE if the last member of reply.entries is the last
entry in the directory or the list reply.entries is
empty and the cookie corresponded to the end of the
directory. If FALSE, there may be more entries to
read.
Otherwise, READDIRPLUS3res.status contains the error on
failure and READDIRPLUS3res.resfail contains the following:
dir_attributes
The attributes of the directory, dir.
IMPLEMENTATION
Issues that need to be understood for this procedure
include increased cache flushing activity on the client
(as new file handles are returned with names which are
entered into caches) and over-the-wire overhead versus
expected subsequent LOOKUP elimination. It is thought that
this procedure may improve performance for directory
browsing where attributes are always required as on the
Apple Macintosh operating system and for MS-DOS.
The dircount and maxcount fields are included as an
optimization. Consider a READDIRPLUS call on a UNIX
operating system implementation for 1048 bytes; the reply
does not contain many entries because of the overhead due
to attributes and file handles. An alternative is to issue
a READDIRPLUS call for 8192 bytes and then only use the
first 1048 bytes of directory information. However, the
server doesn't know that all that is needed is 1048 bytes
of directory information (as would be returned by
READDIR). It sees the 8192 byte request and issues a
VOP_READDIR for 8192 bytes. It then steps through all of
those directory entries, obtaining attributes and file
handles for each entry. When it encodes the result, the
server only encodes until it gets 8192 bytes of results
which include the attributes and file handles. Thus, it
has done a larger VOP_READDIR and many more attribute
fetches than it needed to. The ratio of the directory
entry size to the size of the attributes plus the size of
the file handle is usually at least 8 to 1. The server has
done much more work than it needed to.
The solution to this problem is for the client to provide
two counts to the server. The first is the number of bytes
of directory information that the client really wants,
dircount. The second is the maximum number of bytes in
the result, including the attributes and file handles,
maxcount. Thus, the server will issue a VOP_READDIR for
only the number of bytes that the client really wants to
get, not an inflated number. This should help to reduce
the size of VOP_READDIR requests on the server, thus
reducing the amount of work done there, and to reduce the
number of VOP_LOOKUP, VOP_GETATTR, and other calls done by
the server to construct attributes and file handles.
ERRORS
NFS3ERR_IO
NFS3ERR_ACCES
NFS3ERR_NOTDIR
NFS3ERR_BAD_COOKIE
NFS3ERR_TOOSMALL
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_NOTSUPP
NFS3ERR_SERVERFAULT
SEE ALSO
READDIR.
3.3.18 Procedure 18: FSSTAT - Get dynamic file system information
SYNOPSIS
FSSTAT3res NFSPROC3_FSSTAT(FSSTAT3args) = 18;
struct FSSTAT3args {
nfs_fh3 fsroot;
};
struct FSSTAT3resok {
post_op_attr obj_attributes;
size3 tbytes;
size3 fbytes;
size3 abytes;
size3 tfiles;
size3 ffiles;
size3 afiles;
uint32 invarsec;
};
struct FSSTAT3resfail {
post_op_attr obj_attributes;
};
union FSSTAT3res switch (nfsstat3 status) {
case NFS3_OK:
FSSTAT3resok resok;
default:
FSSTAT3resfail resfail;
};
DESCRIPTION
Procedure FSSTAT retrieves volatile file system state
information. On entry, the arguments in FSSTAT3args are:
fsroot
A file handle identifying a object in the file system.
This is normally a file handle for a mount point for a
file system, as originally obtained from the MOUNT
service on the server.
On successful return, FSSTAT3res.status is NFS3_OK and
FSSTAT3res.resok contains:
obj_attributes
The attributes of the file system object specified in
fsroot.
tbytes
The total size, in bytes, of the file system.
fbytes
The amount of free space, in bytes, in the file
system.
abytes
The amount of free space, in bytes, available to the
user identified by the authentication information in
the RPC. (This reflects space that is reserved by the
file system; it does not reflect any quota system
implemented by the server.)
tfiles
The total number of file slots in the file system. (On
a UNIX server, this often corresponds to the number of
inodes configured.)
ffiles
The number of free file slots in the file system.
afiles
The number of free file slots that are available to the
user corresponding to the authentication information in
the RPC. (This reflects slots that are reserved by the
file system; it does not reflect any quota system
implemented by the server.)
invarsec
A measure of file system volatility: this is the number
of seconds for which the file system is not expected to
change. For a volatile, frequently updated file system,
this will be 0. For an immutable file system, such as a
CD-ROM, this would be the largest unsigned integer. For
file systems that are infrequently modified, for
example, one containing local executable programs and
on-line documentation, a value corresponding to a few
hours or days might be used. The client may use this as
a hint in tuning its cache management. Note however,
this measure is assumed to be dynamic and may change at
any time.
Otherwise, FSSTAT3res.status contains the error on failure
and FSSTAT3res.resfail contains the following:
obj_attributes
The attributes of the file system object specified in
fsroot.
IMPLEMENTATION
Not all implementations can support the entire list of
attributes. It is expected that servers will make a best
effort at supporting all the attributes.
ERRORS
NFS3ERR_IO
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_SERVERFAULT
SEE ALSO
FSINFO.
3.3.19 Procedure 19: FSINFO - Get static file system Information
SYNOPSIS
FSINFO3res NFSPROC3_FSINFO(FSINFO3args) = 19;
const FSF3_LINK = 0x0001;
const FSF3_SYMLINK = 0x0002;
const FSF3_HOMOGENEOUS = 0x0008;
const FSF3_CANSETTIME = 0x0010;
struct FSINFOargs {
nfs_fh3 fsroot;
};
struct FSINFO3resok {
post_op_attr obj_attributes;
uint32 rtmax;
uint32 rtpref;
uint32 rtmult;
uint32 wtmax;
uint32 wtpref;
uint32 wtmult;
uint32 dtpref;
size3 maxfilesize;
nfstime3 time_delta;
uint32 properties;
};
struct FSINFO3resfail {
post_op_attr obj_attributes;
};
union FSINFO3res switch (nfsstat3 status) {
case NFS3_OK:
FSINFO3resok resok;
default:
FSINFO3resfail resfail;
};
DESCRIPTION
Procedure FSINFO retrieves nonvolatile file system state
information and general information about the NFS version
3 protocol server implementation. On entry, the arguments
in FSINFO3args are:
fsroot
A file handle identifying a file object. Normal usage
is to provide a file handle for a mount point for a
file system, as originally obtained from the MOUNT
service on the server.
On successful return, FSINFO3res.status is NFS3_OK and
FSINFO3res.resok contains:
obj_attributes
The attributes of the file system object specified in
fsroot.
rtmax
The maximum size in bytes of a READ request supported
by the server. Any READ with a number greater than
rtmax will result in a short read of rtmax bytes or
less.
rtpref
The preferred size of a READ request. This should be
the same as rtmax unless there is a clear benefit in
performance or efficiency.
rtmult
The suggested multiple for the size of a READ request.
wtmax
The maximum size of a WRITE request supported by the
server. In general, the client is limited by wtmax
since there is no guarantee that a server can handle a
larger write. Any WRITE with a count greater than wtmax
will result in a short write of at most wtmax bytes.
wtpref
The preferred size of a WRITE request. This should be
the same as wtmax unless there is a clear benefit in
performance or efficiency.
wtmult
The suggested multiple for the size of a WRITE
request.
dtpref
The preferred size of a READDIR request.
maxfilesize
The maximum size of a file on the file system.
time_delta
The server time granularity. When setting a file time
using SETATTR, the server guarantees only to preserve
times to this accuracy. If this is {0, 1}, the server
can support nanosecond times, {0, 1000000} denotes
millisecond precision, and {1, 0} indicates that times
are accurate only to the nearest second.
properties
A bit mask of file system properties. The following
values are defined:
FSF_LINK
If this bit is 1 (TRUE), the file system supports
hard links.
FSF_SYMLINK
If this bit is 1 (TRUE), the file system supports
symbolic links.
FSF_HOMOGENEOUS
If this bit is 1 (TRUE), the information returned by
PATHCONF is identical for every file and directory
in the file system. If it is 0 (FALSE), the client
should retrieve PATHCONF information for each file
and directory as required.
FSF_CANSETTIME
If this bit is 1 (TRUE), the server will set the
times for a file via SETATTR if requested (to the
accuracy indicated by time_delta). If it is 0
(FALSE), the server cannot set times as requested.
Otherwise, FSINFO3res.status contains the error on failure
and FSINFO3res.resfail contains the following:
attributes
The attributes of the file system object specified in
fsroot.
IMPLEMENTATION
Not all implementations can support the entire list of
attributes. It is expected that a server will make a best
effort at supporting all the attributes.
The file handle provided is expected to be the file handle
of the file system root, as returned to the MOUNT
operation. Since mounts may occur anywhere within an
exported tree, the server should expect FSINFO requests
specifying file handles within the exported file system.
A server may export different types of file systems with
different attributes returned to the FSINFO call. The
client should retrieve FSINFO information for each mount
completed. Though a server may return different FSINFO
information for different files within a file system,
there is no requirement that a client obtain FSINFO
information for other than the file handle returned at
mount.
The maxfilesize field determines whether a server's
particular file system uses 32 bit sizes and offsets or 64
bit file sizes and offsets. This may affect a client's
processing.
The preferred sizes for requests are nominally tied to an
exported file system mounted by a client. A surmountable
issue arises in that the transfer size for an NFS version
3 protocol request is not only dependent on
characteristics of the file system but also on
characteristics of the network interface, particularly the
maximum transfer unit (MTU). A server implementation can
advertise different transfer sizes (for the fields, rtmax,
rtpref, wtmax, wtpref, and dtpref) depending on the
interface on which the FSINFO request is received. This is
an implementation issue.
ERRORS
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_SERVERFAULT
SEE ALSO
READLINK, WRITE, READDIR, FSSTAT and PATHCONF.
3.3.20 Procedure 20: PATHCONF - Retrieve POSIX information
SYNOPSIS
PATHCONF3res NFSPROC3_PATHCONF(PATHCONF3args) = 20;
struct PATHCONF3args {
nfs_fh3 object;
};
struct PATHCONF3resok {
post_op_attr obj_attributes;
uint32 linkmax;
uint32 name_max;
bool no_trunc;
bool chown_restricted;
bool case_insensitive;
bool case_preserving;
};
struct PATHCONF3resfail {
post_op_attr obj_attributes;
};
union PATHCONF3res switch (nfsstat3 status) {
case NFS3_OK:
PATHCONF3resok resok;
default:
PATHCONF3resfail resfail;
};
DESCRIPTION
Procedure PATHCONF retrieves the pathconf information for
a file or directory. If the FSF_HOMOGENEOUS bit is set in
FSFINFO3resok.properties, the pathconf information will be
the same for all files and directories in the exported
file system in which this file or directory resides. On
entry, the arguments in PATHCONF3args are:
object
The file handle for the file system object.
On successful return, PATHCONF3res.status is NFS3_OK and
PATHCONF3res.resok contains:
obj_attributes
The attributes of the object specified by object.
linkmax
The maximum number of hard links to an object.
name_max
The maximum length of a component of a filename.
no_trunc
If TRUE, the server will reject any request that
includes a name longer than name_max with the error,
NFS3ERR_NAMETOOLONG. If FALSE, any length name over
name_max bytes will be silently truncated to name_max
bytes.
chown_restricted
If TRUE, the server will reject any request to change
either the owner or the group associated with a file if
the caller is not the privileged user. (Uid 0.)
case_insensitive
If TRUE, the server file system does not distinguish
case when interpreting filenames.
case_preserving
If TRUE, the server file system will preserve the case
of a name during a CREATE, MKDIR, MKNOD, SYMLINK,
RENAME, or LINK operation.
Otherwise, PATHCONF3res.status contains the error on
failure and PATHCONF3res.resfail contains the following:
obj_attributes
The attributes of the object specified by object.
IMPLEMENTATION
In some implementations of the NFS version 2 protocol,
pathconf information was obtained at mount time through
the MOUNT protocol. The proper place to obtain it, is as
here, in the NFS version 3 protocol itself.
ERRORS
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_SERVERFAULT
SEE ALSO
LOOKUP, CREATE, MKDIR, SYMLINK, MKNOD, RENAME, LINK and FSINFO.
3.3.21 Procedure 21: COMMIT - Commit cached data on a server to stable storage
SYNOPSIS
COMMIT3res NFSPROC3_COMMIT(COMMIT3args) = 21;
struct COMMIT3args {
nfs_fh3 file;
offset3 offset;
count3 count;
};
struct COMMIT3resok {
wcc_data file_wcc;
writeverf3 verf;
};
struct COMMIT3resfail {
wcc_data file_wcc;
};
union COMMIT3res switch (nfsstat3 status) {
case NFS3_OK:
COMMIT3resok resok;
default:
COMMIT3resfail resfail;
};
DESCRIPTION
プロシージャは、以前UNSTABLEに設定された安定したフィールドを持つWRITEプロシージャの呼び出しで書かれた力や安定したストレージにデータをフラッシュをコミットします。エントリでは、COMMIT3argsの引数は次のとおりです。
file
The file handle for the file to which data is to be
flushed (committed). This must identify a file system
object of type, NF3REG.
offset
The position within the file at which the flush is to
begin. An offset of 0 means to flush data starting at
the beginning of the file.
count
The number of bytes of data to flush. If count is 0, a
flush from offset to the end of file is done.
On successful return, COMMIT3res.status is NFS3_OK and
COMMIT3res.resok contains:
file_wcc
Weak cache consistency data for the file. For a client
that requires only the post-operation file attributes,
these can be found in file_wcc.after.
verf
This is a cookie that the client can use to determine
whether the server has rebooted between a call to WRITE
and a subsequent call to COMMIT. This cookie must be
consistent during a single boot session and must be
unique between instances of the NFS version 3 protocol
server where uncommitted data may be lost.
Otherwise, COMMIT3res.status contains the error on failure
and COMMIT3res.resfail contains the following:
file_wcc
Weak cache consistency data for the file. For a client
that requires only the post-write file attributes,
these can be found in file_wcc.after. Even though the
COMMIT failed, full wcc_data is returned to allow the
client to determine whether the file changed on the
server between calls to WRITE and COMMIT.
IMPLEMENTATION
手順COMMITが操作と意味論でそれをフラッシュし、
ファイルのデータとメタデータのディスクへのディスクを使用してファイルの状態を同期させる
POSIX fsync（2）システムコールに似ています。COMMITが指定されたファイルは、サーバーのディスクに、
サーバー上の任意の非同期データとメタデータをフラッシュし、クライアントに対して同じ操作を実行します。
fsync（2）を同じように、それはいくつか変更されたデータまたは同期させる変更されたデータがあることかもしれません。
データは、サーバーの通常の定期的なバッファ同期活動によって同期されている場合があります。
予期しないエラーが発生した場合を除き、COMMITは常に、NFS3_OKを返します。
COMMITは、（ファイルが完全に書かれている前に、ほとんどのクライアント上のバッファ再生スキームによってトリガされる）ファイルの範囲をフラッシュするためにクライアントのために可能であるという点ではfsync（2）とは異なります。
COMMITのサーバ実装は、合理的に簡単です。
サーバは0とカウントのオフセット0から始まるされている完全なファイルCOMMIT要求を受信した場合、
それはfsyncと同等のものを（）すべき "るファイルです。それ以外の場合は、
オフセットと安定記憶にフラッシュされるようにcountで指定した範囲内でキャッシュされたデータを持っているように手配する必要があります。
両方のケースでは、ファイルに関連付けられたすべてのメタデータは、
返す前に、安定したストレージにフラッシュする必要があります。
サーバ上でフラッシュするものが何もなくなってすることはエラーではありません。
これがフラッシュされるために必要なデータおよびメタデータが既にフラッシュされたり、
最後のサーバー障害時に失われていることを意味します。
COMMITのクライアント実装はもう少し複雑です。安定したストレージにクライアントバッファをコミットしたい理由は2つあります。
最初にクライアントがバッファを再利用したいということです。
このケースでは、オフセットとバッファのカウントがCOMMIT要求時にサーバーに送信されます。
その後、サーバーにフラッシュのオフセットおよびカウントに基づいてキャッシュされたデータを、
フラッシュし、ファイルに関連付けられたメタデータ。
その後、フラッシュとVERF検証のステータスを返します。
COMMITを生成するためのクライアントの他の理由は、終了時に行うことができるよう、
フラッシュの完全なファイルのためのものです。この場合、
クライアントはコミットされていないデータが含まれているこのファイルのバッファのすべてを集めるだろう、
オフセット0と0のカウント、およびそれらのバッファのすべてを、無料でCOMMIT操作を行います。
他のダーティバッファは、通常の方法でサーバに送信されます。
この実装は、クライアント上のバッファ·キャッシュへのいくつかの変更が必要になります。
バッファが安定したUNSTABLEで書き込まれた後、
それがコミット操作によってフラッシュまたはFILE_SYNCまたはDATA_SYNCに安定集合があるWRITE操作で書き込まれるまで、
それはクライアントシステムでダーティとして考慮する必要があります。
これは、データがサーバー上で安定したストレージにフラッシュされる前に解放され再利用されてからバッファを防ぐために行われます。
応答がWRITEまたは予期しないVERFが含まれているCOMMIT操作のいずれかから戻ってきたときに、
クライアントはサーバーにコミットされていないキャッシュされたデータを含むバッファのすべてを再送する必要があります。
実装者にどのようにこれが実行されるまでです。興味のある唯一つのバッファがある場合、
それはおそらく、適切な安定したフラグ付きのWRITE要求に戻って上に送信する必要があります。
複数存在する場合は、それが安定したストレージにサーバー上のすべてのデータをフラッシュするためにCOMMIT操作を再送信して
不安定との安定したセットでのWRITE要求内のバッファのすべてを再送信することができるかもしれません。
これらの再送のタイミングは、実装者に任されている。
上記の説明は、ページキャッシュベースのシステムと同様にバッファ·キャッシュベースのシステムに適用されます。
これらのシステムでは、仮想メモリシステムは、バッファ·キャッシュの代わりに変更する必要があります。
49ページのWRITEの追加コメントを参照してください。
ERRORS
NFS3ERR_IO
NFS3ERR_STALE
NFS3ERR_BADHANDLE
NFS3ERR_SERVERFAULT
SEE ALSO
WRITE.
4. Implementation issues
NFSバージョン3プロトコルは、異なるオペレーティングシステムがファイルを共有できるように設計されています。
しかし、それはUNIX環境で設計されて以来、多くの操作は、UNIXファイルシステムの操作に類似したセマンティクスを持っています。
このセクションでは、一般的な実装固有の詳細と意味問題のいくつかを説明します。
手順の説明は、そのプロシージャの特定の実装のコメントを持っています。
論文の数は、NFSバージョン2プロトコルの実装を構築するときに発生する問題を記述する書かれています。
最高の概要紙はまだある[Sandberg]。 [Israel]、[Macklem]、および[Pawlowski]他の実装について説明します。
[X / OpenNFS] NFSバージョン2プロトコルとサポートプロトコルの完全な説明と同様に、
実装の問題と手順やエラー·意味論についての議論を提供しています。
NFSバージョン3プロトコルの実装を構築するときに、NFSバージョン2プロトコルの実装が検出されます。
構築するときの問題の多くが発生しました。
4.1 Multiple version support
The RPC protocol provides explicit support for versioning of
a service. Client and server implementations of NFS version 3
protocol should support both versions, for full backwards
compatibility, when possible. Default behavior of the RPC
binding protocol is the client and server bind using the
highest version number they both support. Client or server
implementations that cannot easily support both versions (for
example, because of memory restrictions) will have to choose
what version to support. The NFS version 2 protocol would be
a safe choice since fully capable clients and servers should
support both versions. However, this choice would need to be
made keeping all requirements in mind.
4.2 Server/client relationship
The NFS version 3 protocol is designed to allow servers to be
as simple and general as possible. Sometimes the simplicity
of the server can be a problem, if the client implements
complicated file system semantics.
For example, some operating systems allow removal of open
files. A process can open a file and, while it is open,
remove it from the directory. The file can be read and
written as long as the process keeps it open, even though the
file has no name in the file system. It is impossible for a
stateless server to implement these semantics. The client
can do some tricks such as renaming the file on remove (to a
hidden name), and only physically deleting it on close. The
NFS version 3 protocol provides sufficient functionality to
implement most file system semantics on a client.
Every NFS version 3 protocol client can also potentially be a
server, and remote and local mounted file systems can be
freely mixed. This leads to some problems when a client
travels down the directory tree of a remote file system and
reaches the mount point on the server for another remote file
system. Allowing the server to follow the second remote mount
would require loop detection, server lookup, and user
revalidation. Instead, both NFS version 2 protocol and NFS
version 3 protocol implementations do not typically let
clients cross a server's mount point. When a client does a
LOOKUP on a directory on which the server has mounted a file
system, the client sees the underlying directory instead of
the mounted directory.
For example, if a server has a file system called /usr and
mounts another file system on /usr/src, if a client mounts
/usr, it does not see the mounted version of /usr/src. A
client could do remote mounts that match the server's mount
points to maintain the server's view. In this example, the
client would also have to mount /usr/src in addition to /usr,
even if they are from the same server.
4.3 Path name interpretation
There are a few complications to the rule that path names are
always parsed on the client. For example, symbolic links
could have different interpretations on different clients.
There is no answer to this problem in this specification.
Another common problem for non-UNIX implementations is the
special interpretation of the pathname, "..", to mean the
parent of a given directory. A future revision of the
protocol may use an explicit flag to indicate the parent
instead - however it is not a problem as many working
non-UNIX implementations exist.
4.4 Permission issues
The NFS version 3 protocol, strictly speaking, does not
define the permission checking used by servers. However, it
is expected that a server will do normal operating system
permission checking using AUTH_UNIX style authentication as
the basis of its protection mechanism, or another stronger
form of authentication such as AUTH_DES or AUTH_KERB. With
AUTH_UNIX authentication, the server gets the client's
effective uid, effective gid, and groups on each call and
uses them to check permission. These are the so-called UNIX
credentials. AUTH_DES and AUTH_KERB use a network name, or
netname, as the basis for identification (from which a UNIX
server derives the necessary standard UNIX credentials).
There are problems with this method that have been solved.
Using uid and gid implies that the client and server share
the same uid list. Every server and client pair must have the
same mapping from user to uid and from group to gid. Since
every client can also be a server, this tends to imply that
the whole network shares the same uid/gid space. If this is
not the case, then it usually falls upon the server to
perform some custom mapping of credentials from one
authentication domain into another. A discussion of
techniques for managing a shared user space or for providing
mechanisms for user ID mapping is beyond the scope of this
specification.
Another problem arises due to the usually stateful open
operation. Most operating systems check permission at open
time, and then check that the file is open on each read and
write request. With stateless servers, the server cannot
detect that the file is open and must do permission checking
on each read and write call. UNIX client semantics of access
permission checking on open can be provided with the ACCESS
procedure call in this revision, which allows a client to
explicitly check access permissions without resorting to
trying the operation. On a local file system, a user can open
a file and then change the permissions so that no one is
allowed to touch it, but will still be able to write to the
file because it is open. On a remote file system, by
contrast, the write would fail. To get around this problem,
the server's permission checking algorithm should allow the
owner of a file to access it regardless of the permission
setting. This is needed in a practical NFS version 3 protocol
server implementation, but it does depart from correct local
file system semantics. This should not affect the return
result of access permissions as returned by the ACCESS
procedure, however.
A similar problem has to do with paging in an executable
program over the network. The operating system usually checks
for execute permission before opening a file for demand
paging, and then reads blocks from the open file. In a local
UNIX file system, an executable file does not need read
permission to execute (pagein). An NFS version 3 protocol
server can not tell the difference between a normal file read
(where the read permission bit is meaningful) and a demand
pagein read (where the server should allow access to the
executable file if the execute bit is set for that user or
group or public). To make this work, the server allows
reading of files if the uid given in the call has either
execute or read permission on the file, through ownership,
group membership or public access. Again, this departs from
correct local file system semantics.
In most operating systems, a particular user (on UNIX, the
uid 0) has access to all files, no matter what permission and
ownership they have. This superuser permission may not be
allowed on the server, since anyone who can become superuser
on their client could gain access to all remote files. A UNIX
server by default maps uid 0 to a distinguished value
(UID_NOBODY), as well as mapping the groups list, before
doing its access checking. A server implementation may
provide a mechanism to change this mapping. This works except
for NFS version 3 protocol root file systems (required for
diskless NFS version 3 protocol client support), where
superuser access cannot be avoided. Export options are used,
on the server, to restrict the set of clients allowed
superuser access.
4.5 Duplicate request cache
典型的なNFSバージョン3プロトコルの障害復旧モデルは、クライアントのタイムアウトを使用し、
サーバーのクラッシュ、ネットワークパーティション、および失われたサーバの応答を処理するために再試行します。
再試行された要求は、元の重複と呼ばれています。
ファイルサーバーのコンテキストで使用される場合において、「冪」とは、操作の種類を区別するために使用することができます。
冪等要求は、サーバが同等の結果（これは実際の変更には、副作用として、ファイルのアクセス時間は、READのために言うかもしれませんが）
で複数回実行することができているものです。いくつかのNFS操作が明らかに非多重呼び出し不変である。
二度目にしようとした場合、彼らが失敗する可能性がありますので、彼らは、
単に特別な注意なしで再処理することはできません。
CREATE要求は、例えば、所有者が書き込み権限を持っていないためにファイルを作成するために使用することができます。
オリジナルが成功した場合は、この要求の複製は成功しません。同様に、ファイルは一度だけ削除することができます。
重複した非べき等の要求を実行することによって引き起こされる副作用（例えば、失われた原因と切り捨て操作は書き込み）
破壊することができます。信頼できないネットワーク·トランスポート（UDP）の一般的な選択肢とステートレス設計の組み合わせにより、
非べき等の要求の破壊的な再生の可能性を意味します。より正確になるが、それは上でもNFSバージョン3プロトコル実装であるため、
非べき等の要求の破壊的な再生の可能性を得られる信頼性のRPCメカニズムの上にNFSバージョン3プロトコルの
本質的なステートレスな設計です。信頼性の高い接続指向のトランスポートは、
自動再確立と接続の切断は、重複する要求の処理（クライアントが要求を再送信し、サーバは潜在的な重複した非べき等の要求に対処する必要があります）が必要です。
ほとんどのNFSv3プロトコルサーバ実装が重複し非べき等の要求の処理のための最近のリクエストのキャッシュを（重複要求キャッシュと呼ばれる）を使用します。
重複要求キャッシュは、リクエストの元の完成状態が記憶された短期記憶のメカニズムを提供し、操作は一度だけ試みた。
このリクエストの重複コピーが受信された場合、元の完了ステータスが返されます。
重複要求キャッシュのメカニズムは、重複するNFSバージョン3プロトコルのリクエストによって引き起こされる破壊的な副作用を減らすのに役立っています。
このメカニズムは、しかしながら、すべての故障モードでこれらの破壊的な副作用に対して保証するものではありません。
ほとんどのサーバーは、RAM内の重複要求キャッシュを格納するので、内容はサーバがクラッシュした場合失われます。
この例外は、おそらくファイルシステム自体は、重複要求キャッシュの状態を共有するために使用される高可用性、
冗長サーバへのアプローチで発生する可能性があります。
キャッシュがサーバの再起動（または高可用性の場合のフェールオーバー）を存続しても、その効果は、そのサイズの関数である。
ネットワークパーティションは、クライアントが対応する要求に対する応答を受信する前にキャッシュ·エントリが再利用されることがあります。
この問題が発生した場合は、重複した要求は、おそらく破壊的な副作用は、新しいものとして処理されます。
重複要求キャッシュの実装および使用の適切な説明は[Juszczak]で見つけることができます。
4.6 File name component handling
Server implementations of NFS version 3 protocol will frequently impose restrictions on the names which can be created. Many servers will also forbid the use of names that
contain certain characters, such as the path component separator used by the server operating system. For example, the UFS file system will reject a name which contains "/",
while "." and ".." are distinguished in UFS, and may not be specified as the name when creating a file system object. The exact error status values return for these errors is
specified in the description of each procedure argument. The values (which conform to NFS version 2 protocol server practice) are not necessarily obvious, nor are they
consistent from one procedure to the next.
4.7 Synchronous modifying operations
Data-modifying operations in the NFS version 3 protocol are synchronous. When a procedure returns to the client, the client can assume that the operation has completed and any
data associated with the request is now on stable storage.
4.8 Stable storage
NFS version 3 protocol servers must be able to recover without data loss from multiple power failures (including cascading power failures, that is, several power failures in
quick succession), operating system failures, and hardware failure of components other than the storage medium itself (for example, disk, nonvolatile RAM).
Some examples of stable storage that are allowable for an NFS server include:
1. Media commit of data, that is, the modified data has
been successfully written to the disk media, for example,
the disk platter.
2. An immediate reply disk drive with battery-backed
on-drive intermediate storage or uninterruptible power
system (UPS).
3. Server commit of data with battery-backed intermediate
storage and recovery software.
4. Cache commit with uninterruptible power system (UPS) and
recovery software.
Conversely, the following are not examples of stable storage:
1. An immediate reply disk drive without battery-backed
on-drive intermediate storage or uninterruptible power
system (UPS).
2. Cache commit without both uninterruptible power system
(UPS) and recovery software.
The only exception to this (introduced in this protocol
revision) is as described under the WRITE procedure on the
handling of the stable bit, and the use of the COMMIT
procedure. It is the use of the synchronous COMMIT procedure
that provides the necessary semantic support in the NFS
version 3 protocol.
4.9 Lookups and name resolution
A common objection to the NFS version 3 protocol is the
philosophy of component-by-component LOOKUP by the client in
resolving a name. The objection is that this is inefficient,
as latencies for component-by-component LOOKUP would be
unbearable.
Implementation practice solves this issue. A name cache,
providing component to file-handle mapping, is kept on the
client to short circuit actual LOOKUP invocations over the
wire. The cache is subject to cache timeout parameters that
bound attributes.
4.10 Adaptive retransmission
Most client implementations use either an exponential
back-off strategy to some maximum retransmission value, or a
more adaptive strategy that attempts congestion avoidance.
Congestion avoidance schemes in NFS request retransmission
are modelled on the work presented in [Jacobson]. [Nowicki]
and [Macklem] describe congestion avoidance schemes to be
applied to the NFS protocol over UDP.
4.11 Caching policies
NFSバージョン3プロトコルは、クライアントまたはサーバー上のキャッシュのポリシーを定義していません。特にありません
クライアントとサーバの間の、また別のクライアントの間に厳密なキャッシュの一貫性を保つためにサポートされています。
いくつかの分散ファイルシステムのキャッシュの同期化とメカニズムの問題についての議論のための[Kazar]を参照してください。
4.12 Stable versus unstable writes
The setting of the stable field in the WRITE arguments, that
is whether or not to do asynchronous WRITE requests, is
straightforward on a UNIX client. If the NFS version 3
protocol client receives a write request that is not marked
as being asynchronous, it should generate the RPC with stable
set to TRUE. If the request is marked as being asynchronous,
the RPC should be generated with stable set to FALSE. If the
response comes back with the committed field set to TRUE, the
client should just mark the write request as done and no
further action is required. If committed is set to FALSE,
indicating that the buffer was not synchronized with the
server's disk, the client will need to mark the buffer in
some way which indicates that a copy of the buffer lives on
the server and that a new copy does not need to be sent to
the server, but that a commit is required.
Note that this algorithm introduces a new state for buffers,
thus there are now three states for buffers. The three states
are dirty, done but needs to be committed, and done. This
extra state on the client will likely require modifications
to the system outside of the NFS version 3 protocol client.
One proposal that was rejected was the addition of a boolean
commit argument to the WRITE operation. It would be used to
indicate whether the server should do a full file commit
after doing the write. This seems as if it could be useful if
the client knew that it was doing the last write on the file.
It is difficult to see how this could be used, given existing
client architectures though.
The asynchronous write opens up the window of problems
associated with write sharing. For example: client A writes
some data asynchronously. Client A is still holding the
buffers cached, waiting to commit them later. Client B reads
the modified data and writes it back to the server. The
server then crashes. When it comes back up, client A issues a
COMMIT operation which returns with a different cookie as
well as changed attributes. In this case, the correct action
may or may not be to retransmit the cached buffers.
Unfortunately, client A can't tell for sure, so it will need
to retransmit the buffers, thus overwriting the changes from
client B. Fortunately, write sharing is rare and the
solution matches the current write sharing situation. Without
using locking for synchronization, the behaviour will be
indeterminate.
In a high availability (redundant system) server
implementation, two cases exist which relate to the verf
changing. If the high availability server implementation
does not use a shared-memory scheme, then the verf should
change on failover, since the unsynchronized data is not
available to the second processor and there is no guarantee
that the system which had the data cached was able to flush
it to stable storage before going down. The client will need
to retransmit the data to be safe. In a shared-memory high
availability server implementation, the verf would not need
to change because the server would still have the cached data
available to it to be flushed. The exact policy regarding the
verf in a shared memory high availability implementation,
however, is up to the server implementor.
4.13 32 bit clients/servers and 64 bit clients/servers
The 64 bit nature of the NFS version 3 protocol introduces
several compatibility problems. The most notable two are
mismatched clients and servers, that is, a 32 bit client and
a 64 bit server or a 64 bit client and a 32 bit server.
The problems of a 64 bit client and a 32 bit server are easy
to handle. The client will never encounter a file that it can
not handle. If it sends a request to the server that the
server can not handle, the server should reject the request
with an appropriate error.
The problems of a 32 bit client and a 64 bit server are much
harder to handle. In this situation, the server does not have
a problem because it can handle anything that the client can
generate. However, the client may encounter a file that it
can not handle. The client will not be able to handle a file
whose size can not be expressed in 32 bits. Thus, the client
will not be able to properly decode the size of the file into
its local attributes structure. Also, a file can grow beyond
the limit of the client while the client is accessing the
file.
The solutions to these problems are left up to the individual
implementor. However, there are two common approaches used to
resolve this situation. The implementor can choose between
them or even can invent a new solution altogether.
The most common solution is for the client to deny access to
any file whose size can not be expressed in 32 bits. This is
probably the safest, but does introduce some strange
semantics when the file grows beyond the limit of the client
while it is being access by that client. The file becomes
inaccessible even while it is being accessed.
The second solution is for the client to map any size greater
than it can handle to the maximum size that it can handle.
Effectively, it is lying to the application program. This
allows the application access as much of the file as possible
given the 32 bit offset restriction. This eliminates the
strange semantic of the file effectively disappearing after
it has been accessed, but does introduce other problems. The
client will not be able to access the entire file.
Currently, the first solution is the recommended solution.
However, client implementors are encouraged to do the best
that they can to reduce the effects of this situation.
5.0 Appendix I: Mount protocol
The changes from the NFS version 2 protocol to the NFS version 3
protocol have required some changes to be made in the MOUNT
protocol. To meet the needs of the NFS version 3 protocol, a
new version of the MOUNT protocol has been defined. This new
protocol satisfies the requirements of the NFS version 3
protocol and addresses several other current market
requirements.
5.1 RPC Information
5.1.1 Authentication
The MOUNT service uses AUTH_NONE in the NULL procedure.
AUTH_UNIX, AUTH_SHORT, AUTH_DES, or AUTH_KERB are used for all other procedures. Other authentication types may be supported in the future.
5.1.2 Constants
These are the RPC constants needed to call the MOUNT service.
They are given in decimal.
PROGRAM 100005
VERSION 3
5.1.3 Transport address
The MOUNT service is normally supported over the TCP and UDP protocols. The rpcbind daemon should be queried for the correct transport address.
5.1.4 Sizes
const MNTPATHLEN = 1024; /* Maximum bytes in a path name */
const MNTNAMLEN = 255; /* Maximum bytes in a name */
const FHSIZE3 = 64; /* Maximum bytes in a V3 file handle */
5.1.5 Basic Data Types
typedef opaque fhandle3<FHSIZE3>;
typedef string dirpath<MNTPATHLEN>;
typedef string name<MNTNAMLEN>;
enum mountstat3 {
MNT3_OK = 0, /* no error */
MNT3ERR_PERM = 1, /* Not owner */
MNT3ERR_NOENT = 2, /* No such file or directory */
MNT3ERR_IO = 5, /* I/O error */
MNT3ERR_ACCES = 13, /* Permission denied */
MNT3ERR_NOTDIR = 20, /* Not a directory */
MNT3ERR_INVAL = 22, /* Invalid argument */
MNT3ERR_NAMETOOLONG = 63, /* Filename too long */
MNT3ERR_NOTSUPP = 10004, /* Operation not supported */
MNT3ERR_SERVERFAULT = 10006 /* A failure on the server */
};
5.2 Server Procedures
The following sections define the RPC procedures supplied by a MOUNT version 3 protocol server. The RPC procedure number is given at the top of the page with the name and version. The SYNOPSIS provides the name of the procedure, the list of the names of the arguments, the list of the names of the results, followed by the XDR argument declarations and results declarations. The information in the SYNOPSIS is specified in RPC Data Description Language as defined in [RFC1014]. The
DESCRIPTION section tells what the procedure is expected to do and how its arguments and results are used. The ERRORS section lists the errors returned for specific types of failures. The IMPLEMENTATION field describes how the procedure is expected to work and how it should be used by clients.
program MOUNT_PROGRAM {
version MOUNT_V3 {
void MOUNTPROC3_NULL(void) = 0;
mountres3 MOUNTPROC3_MNT(dirpath) = 1;
mountlist MOUNTPROC3_DUMP(void) = 2;
void MOUNTPROC3_UMNT(dirpath) = 3;
void MOUNTPROC3_UMNTALL(void) = 4;
exports MOUNTPROC3_EXPORT(void) = 5;
} = 3;
} = 100005;
5.2.0 Procedure 0: Null - Do nothing
SYNOPSIS
void MOUNTPROC3_NULL(void) = 0;
DESCRIPTION
Procedure NULL does not do any work. It is made available
to allow server response testing and timing.
IMPLEMENTATION
It is important that this procedure do no work at all so
that it can be used to measure the overhead of processing
a service request. By convention, the NULL procedure
should never require any authentication. A server may
choose to ignore this convention, in a more secure
implementation, where responding to the NULL procedure
call acknowledges the existence of a resource to an
unauthenticated client.
ERRORS
Since the NULL procedure takes no MOUNT protocol arguments
and returns no MOUNT protocol response, it can not return
a MOUNT protocol error. However, it is possible that some
server implementations may return RPC errors based on
security and authentication requirements.
5.2.1 Procedure 1: MNT - Add mount entry
SYNOPSIS
mountres3 MOUNTPROC3_MNT(dirpath) = 1;
struct mountres3_ok {
fhandle3 fhandle;
int auth_flavors<>;
};
union mountres3 switch (mountstat3 fhs_status) {
case MNT_OK:
mountres3_ok mountinfo;
default:
void;
};
DESCRIPTION
Procedure MNT maps a pathname on the server to a file
handle. The pathname is an ASCII string that describes a
directory on the server. If the call is successful
(MNT3_OK), the server returns an NFS version 3 protocol
file handle and a vector of RPC authentication flavors
that are supported with the client's use of the file
handle (or any file handles derived from it). The
authentication flavors are defined in Section 7.2 and
section 9 of [RFC1057].
IMPLEMENTATION
If mountres3.fhs_status is MNT3_OK, then
mountres3.mountinfo contains the file handle for the
directory and a list of acceptable authentication
flavors. This file handle may only be used in the NFS
version 3 protocol. This procedure also results in the
server adding a new entry to its mount list recording that
this client has mounted the directory. AUTH_UNIX
authentication or better is required.
ERRORS
MNT3ERR_NOENT
MNT3ERR_IO
MNT3ERR_ACCES
MNT3ERR_NOTDIR
MNT3ERR_NAMETOOLONG
5.2.2 Procedure 2: DUMP - Return mount entries
SYNOPSIS
mountlist MOUNTPROC3_DUMP(void) = 2;
typedef struct mountbody *mountlist;
struct mountbody {
name ml_hostname;
dirpath ml_directory;
mountlist ml_next;
};
DESCRIPTION
Procedure DUMP returns the list of remotely mounted file
systems. The mountlist contains one entry for each client
host name and directory pair.
IMPLEMENTATION
This list is derived from a list maintained on the server
of clients that have requested file handles with the MNT
procedure. Entries are removed from this list only when a
client calls the UMNT or UMNTALL procedure. Entries may
become stale if a client crashes and does not issue either
UMNT calls for all of the file systems that it had
previously mounted or a UMNTALL to remove all entries that
existed for it on the server.
ERRORS
There are no MOUNT protocol errors which can be returned
from this procedure. However, RPC errors may be returned
for authentication or other RPC failures.
5.2.3 Procedure 3: UMNT - Remove mount entry
SYNOPSIS
void MOUNTPROC3_UMNT(dirpath) = 3;
DESCRIPTION
Procedure UMNT removes the mount list entry for the
directory that was previously the subject of a MNT call
from this client. AUTH_UNIX authentication or better is
required.
IMPLEMENTATION
Typically, server implementations have maintained a list
of clients which have file systems mounted. In the past,
this list has been used to inform clients that the server
was going to be shutdown.
ERRORS
There are no MOUNT protocol errors which can be returned
from this procedure. However, RPC errors may be returned
for authentication or other RPC failures.
5.2.4 Procedure 4: UMNTALL - Remove all mount entries
SYNOPSIS
void MOUNTPROC3_UMNTALL(void) = 4;
DESCRIPTION
Procedure UMNTALL removes all of the mount entries for
this client previously recorded by calls to MNT. AUTH_UNIX
authentication or better is required.
IMPLEMENTATION
This procedure should be used by clients when they are
recovering after a system shutdown. If the client could
not successfully unmount all of its file systems before
being shutdown or the client crashed because of a software
or hardware problem, there may be servers which still have
mount entries for this client. This is an easy way for the
client to inform all servers at once that it does not have
any mounted file systems. However, since this procedure
is generally implemented using broadcast RPC, it is only
of limited usefullness.
ERRORS
There are no MOUNT protocol errors which can be returned
from this procedure. However, RPC errors may be returned
for authentication or other RPC failures.
5.2.5 Procedure 5: EXPORT - Return export list
SYNOPSIS
exports MOUNTPROC3_EXPORT(void) = 5;
typedef struct groupnode *groups;
struct groupnode {
name gr_name;
groups gr_next;
};
typedef struct exportnode *exports;
struct exportnode {
dirpath ex_dir;
groups ex_groups;
exports ex_next;
};
DESCRIPTION
Procedure EXPORT returns a list of all the exported file
systems and which clients are allowed to mount each one.
The names in the group list are implementation-specific
and cannot be directly interpreted by clients. These names
can represent hosts or groups of hosts.
IMPLEMENTATION
This procedure generally returns the contents of a list of
shared or exported file systems. These are the file
systems which are made available to NFS version 3 protocol
clients.
ERRORS
There are no MOUNT protocol errors which can be returned
from this procedure. However, RPC errors may be returned
for authentication or other RPC failures.
6.0 Appendix II: Lock manager protocol
Because the NFS version 2 protocol as well as the NFS version 3
protocol is stateless, an additional Network Lock Manager (NLM)
protocol is required to support locking of NFS-mounted files.
The NLM version 3 protocol, which is used with the NFS version 2
protocol, is documented in [X/OpenNFS].
Some of the changes in the NFS version 3 protocol require a
new version of the NLM protocol. This new protocol is the NLM
version 4 protocol. The following table summarizes the
correspondence between versions of the NFS protocol and NLM
protocol.
NFS and NLM protocol compatibility
+---------+---------+
| NFS | NLM |
| Version | Version |
+===================+
| 2 | 1,3 |
+---------+---------+
| 3 | 4 |
+---------+---------+
This appendix only discusses the differences between the NLM
version 3 protocol and the NLM version 4 protocol. As in the
NFS version 3 protocol, almost all the names in the NLM version
4 protocol have been changed to include a version number. This
appendix does not discuss changes that consist solely of a name
change.
6.1 RPC Information
6.1.1 Authentication
The NLM service uses AUTH_NONE in the NULL procedure.
AUTH_UNIX, AUTH_SHORT, AUTH_DES, and AUTH_KERB are used for all other procedures. Other authentication types may be supported in the future.
6.1.2 Constants
These are the RPC constants needed to call the NLM service.
They are given in decimal.
PROGRAM 100021
VERSION 4
6.1.3 Transport Address
The NLM service is normally supported over the TCP and UDP
protocols. The rpcbind daemon should be queried for the
correct transport address.
6.1.4 Basic Data Types
uint64
typedef unsigned hyper uint64;
int64
typedef hyper int64;
uint32
typedef unsigned long uint32;
int32
typedef long int32;
These types are new for the NLM version 4 protocol. They are
the same as in the NFS version 3 protocol.
nlm4_stats
enum nlm4_stats {
NLM4_GRANTED = 0,
NLM4_DENIED = 1,
NLM4_DENIED_NOLOCKS = 2,
NLM4_BLOCKED = 3,
NLM4_DENIED_GRACE_PERIOD = 4,
NLM4_DEADLCK = 5,
NLM4_ROFS = 6,
NLM4_STALE_FH = 7,
NLM4_FBIG = 8,
NLM4_FAILED = 9
};
Nlm4_stats indicates the success or failure of a call. This
version contains several new error codes, so that clients can
provide more precise failure information to applications.
NLM4_GRANTED
The call completed successfully.
NLM4_DENIED
The call failed. For attempts to set a lock, this status
implies that if the client retries the call later, it may
succeed.
NLM4_DENIED_NOLOCKS
The call failed because the server could not allocate the
necessary resources.
NLM4_BLOCKED
Indicates that a blocking request cannot be granted
immediately. The server will issue an NLMPROC4_GRANTED
callback to the client when the lock is granted.
NLM4_DENIED_GRACE_PERIOD
The call failed because the server is reestablishing old
locks after a reboot and is not yet ready to resume normal
service.
NLM4_DEADLCK
The request could not be granted and blocking would cause
a deadlock.
NLM4_ROFS
The call failed because the remote file system is
read-only. For example, some server implementations might
not support exclusive locks on read-only file systems.
NLM4_STALE_FH
The call failed because it uses an invalid file handle.
This can happen if the file has been removed or if access
to the file has been revoked on the server.
NLM4_FBIG
The call failed because it specified a length or offset
that exceeds the range supported by the server.
NLM4_FAILED
The call failed for some reason not already listed. The
client should take this status as a strong hint not to
retry the request.
nlm4_holder
struct nlm4_holder {
bool exclusive;
int32 svid;
netobj oh;
uint64 l_offset;
uint64 l_len;
};
This structure indicates the holder of a lock. The exclusive
field tells whether the holder has an exclusive lock or a
shared lock. The svid field identifies the process that is
holding the lock. The oh field is an opaque object that
identifies the host or process that is holding the lock. The
l_len and l_offset fields identify the region that is locked.
The only difference between the NLM version 3 protocol and
the NLM version 4 protocol is that in the NLM version 3
protocol, the l_len and l_offset fields are 32 bits wide,
while they are 64 bits wide in the NLM version 4 protocol.
nlm4_lock
struct nlm4_lock {
string caller_name<LM_MAXSTRLEN>;
netobj fh;
netobj oh;
int32 svid;
uint64 l_offset;
uint64 l_len;
};
This structure describes a lock request. The caller_name
field identifies the host that is making the request. The fh
field identifies the file to lock. The oh field is an opaque
object that identifies the host or process that is making the
request, and the svid field identifies the process that is
making the request. The l_offset and l_len fields identify
the region of the file that the lock controls. A l_len of 0
means "to end of file".
There are two differences between the NLM version 3 protocol
and the NLM version 4 protocol versions of this structure.
First, in the NLM version 3 protocol, the length and offset
are 32 bits wide, while they are 64 bits wide in the NLM
version 4 protocol. Second, in the NLM version 3 protocol,
the file handle is a fixed-length NFS version 2 protocol file
handle, which is encoded as a byte count followed by a byte
array. In the NFS version 3 protocol, the file handle is
already variable-length, so it is copied directly into the fh
field. That is, the first four bytes of the fh field are the
same as the byte count in an NFS version 3 protocol nfs_fh3.
The rest of the fh field contains the byte array from the NFS
version 3 protocol nfs_fh3.
nlm4_share
struct nlm4_share {
string caller_name<LM_MAXSTRLEN>;
netobj fh;
netobj oh;
fsh4_mode mode;
fsh4_access access;
};
This structure is used to support DOS file sharing. The
caller_name field identifies the host making the request.
The fh field identifies the file to be operated on. The oh
field is an opaque object that identifies the host or process
that is making the request. The mode and access fields
specify the file-sharing and access modes. The encoding of fh
is a byte count, followed by the file handle byte array. See
the description of nlm4_lock for more details.
6.2 NLM Procedures
The procedures in the NLM version 4 protocol are semantically the same as those in the NLM version 3 protocol. The only
semantic difference is the addition of a NULL procedure that can be used to test for server responsiveness. The procedure
names with _MSG and _RES suffixes denote asynchronous messages; for these the void response implies no reply. A
syntactic change is that the procedures were renamed to avoid name conflicts with the values of nlm4_stats. Thus the
procedure definition is as follows.
version NLM4_VERS {
void
NLMPROC4_NULL(void) = 0;
nlm4_testres
NLMPROC4_TEST(nlm4_testargs) = 1;
nlm4_res
NLMPROC4_LOCK(nlm4_lockargs) = 2;
nlm4_res
NLMPROC4_CANCEL(nlm4_cancargs) = 3;
nlm4_res
NLMPROC4_UNLOCK(nlm4_unlockargs) = 4;
nlm4_res
NLMPROC4_GRANTED(nlm4_testargs) = 5;
void
NLMPROC4_TEST_MSG(nlm4_testargs) = 6;
void
NLMPROC4_LOCK_MSG(nlm4_lockargs) = 7;
void
NLMPROC4_CANCEL_MSG(nlm4_cancargs) = 8;
void
NLMPROC4_UNLOCK_MSG(nlm4_unlockargs) = 9;
void
NLMPROC4_GRANTED_MSG(nlm4_testargs) = 10;
void
NLMPROC4_TEST_RES(nlm4_testres) = 11;
void
NLMPROC4_LOCK_RES(nlm4_res) = 12;
void
NLMPROC4_CANCEL_RES(nlm4_res) = 13;
void
NLMPROC4_UNLOCK_RES(nlm4_res) = 14;
void
NLMPROC4_GRANTED_RES(nlm4_res) = 15;
nlm4_shareres
NLMPROC4_SHARE(nlm4_shareargs) = 20;
nlm4_shareres
NLMPROC4_UNSHARE(nlm4_shareargs) = 21;
nlm4_res
NLMPROC4_NM_LOCK(nlm4_lockargs) = 22;
void
NLMPROC4_FREE_ALL(nlm4_notify) = 23;
} = 4;
6.2.0 Procedure 0: NULL - Do nothing
SYNOPSIS
void NLMPROC4_NULL(void) = 0;
DESCRIPTION
The NULL procedure does no work. It is made available in
all RPC services to allow server response testing and
timing.
IMPLEMENTATION
It is important that this procedure do no work at all so
that it can be used to measure the overhead of processing
a service request. By convention, the NULL procedure
should never require any authentication.
ERRORS
It is possible that some server implementations may return
RPC errors based on security and authentication
requirements.
6.3 Implementation issues
6.3.1 64-bit offsets and lengths
Some NFS version 3 protocol servers can only support requests where the file offset or length fits in 32 or
fewer bits. For these servers, the lock manager will have the same restriction. If such a lock manager receives a
request that it cannot handle (because the offset or length uses more than 32 bits), it should return the error, NLM4_FBIG.
6.3.2 File handles
The change in the file handle format from the NFS version 2 protocol to the NFS version 3 protocol complicates the
lock manager. First, the lock manager needs some way to tell when an NFS version 2 protocol file handle refers to
the same file as an NFS version 3 protocol file handle.
(This is assuming that the lock manager supports both NLM version 3 protocol clients and NLM version 4 protocol
clients.) Second, if the lock manager runs the file handle through a hashing function, the hashing function may need
to be retuned to work with NFS version 3 protocol file handles as well as NFS version 2 protocol file handles.
7.0 Appendix III: Bibliography
[Corbin] Corbin, John, "The Art of Distributed
Programming-Programming Techniques for Remote
Procedure Calls." Springer-Verlag, New York, New
York. 1991. Basic description of RPC and XDR
and how to program distributed applications
using them.
[Glover] Glover, Fred, "TNFS Protocol Specification,"
Trusted System Interest Group, Work in
Progress.
[Israel] Israel, Robert K., Sandra Jett, James Pownell,
George M. Ericson, "Eliminating Data Copies in
UNIX-based NFS Servers," Uniforum Conference
Proceedings, San Francisco, CA,
February 27 - March 2, 1989. Describes two
methods for reducing data copies in NFS server
code.
[Jacobson] Jacobson, V., "Congestion Control and
Avoidance," Proc. ACM SIGCOMM `88, Stanford, CA,
August 1988. The paper describing improvements
to TCP to allow use over Wide Area Networks and
through gateways connecting networks of varying
capacity. This work was a starting point for the
NFS Dynamic Retransmission work.
[Juszczak] Juszczak, Chet, "Improving the Performance and
Correctness of an NFS Server," USENIX Conference
Proceedings, USENIX Association, Berkeley, CA,
June 1990, pages 53-63. Describes reply cache
implementation that avoids work in the server by
handling duplicate requests. More important,
though listed as a side-effect, the reply cache
aids in the avoidance of destructive
non-idempotent operation re-application --
improving correctness.
[Kazar] Kazar, Michael Leon, "Synchronization and Caching
Issues in the Andrew File System," USENIX Conference
Proceedings, USENIX Association, Berkeley, CA,
Dallas Winter 1988, pages 27-36. A description
of the cache consistency scheme in AFS.
Contrasted with other distributed file systems.
[Macklem] Macklem, Rick, "Lessons Learned Tuning the
4.3BSD Reno Implementation of the NFS Protocol,"
Winter USENIX Conference Proceedings, USENIX
Association, Berkeley, CA, January 1991.
Describes performance work in tuning the 4.3BSD
Reno NFS implementation. Describes performance
improvement (reduced CPU loading) through
elimination of data copies.
[Mogul] Mogul, Jeffrey C., "A Recovery Protocol for Spritely
NFS," USENIX File System Workshop Proceedings,
Ann Arbor, MI, USENIX Association, Berkeley, CA,
May 1992. Second paper on Spritely NFS proposes
a lease-based scheme for recovering state of
consistency protocol.
[Nowicki] Nowicki, Bill, "Transport Issues in the Network
File System," ACM SIGCOMM newsletter Computer
Communication Review, April 1989. A brief
description of the basis for the dynamic
retransmission work.
[Pawlowski] Pawlowski, Brian, Ron Hixon, Mark Stein, Joseph
Tumminaro, "Network Computing in the UNIX and
IBM Mainframe Environment," Uniforum `89 Conf.
Proc., (1989) Description of an NFS server
implementation for IBM's MVS operating system.
[RFC1014] Sun Microsystems, Inc., "XDR: External Data
Representation Standard", RFC 1014,
Sun Microsystems, Inc., June 1987.
Specification for canonical format for data
exchange, used with RPC.
[RFC1057] Sun Microsystems, Inc., "RPC: Remote Procedure
Call Protocol Specification", RFC 1057,
Sun Microsystems, Inc., June 1988.
Remote procedure protocol specification.
[RFC1094] Sun Microsystems, Inc., "Network Filesystem
Specification", RFC 1094, Sun Microsystems, Inc.,
March 1989. NFS version 2 protocol
specification.
[Sandberg] Sandberg, R., D. Goldberg, S. Kleiman, D. Walsh,
B. Lyon, "Design and Implementation of the Sun
Network Filesystem," USENIX Conference
Proceedings, USENIX Association, Berkeley, CA,
Summer 1985. The basic paper describing the
SunOS implementation of the NFS version 2
protocol, and discusses the goals, protocol
specification and trade-offs.
[Srinivasan] Srinivasan, V., Jeffrey C. Mogul, "Spritely
NFS: Implementation and Performance of Cache
Consistency Protocols", WRL Research Report
89/5, Digital Equipment Corporation Western
Research Laboratory, 100 Hamilton Ave., Palo
Alto, CA, 94301, May 1989. This paper analyzes
the effect of applying a Sprite-like consistency
protocol applied to standard NFS. The issues of
recovery in a stateful environment are covered
in [Mogul].
[X/OpenNFS] X/Open Company, Ltd., X/Open CAE Specification:
Protocols for X/Open Internetworking: XNFS,
X/Open Company, Ltd., Apex Plaza, Forbury Road,
Reading Berkshire, RG1 1AX, United Kingdom,
1991. This is an indispensable reference for
NFS version 2 protocol and accompanying
protocols, including the Lock Manager and the
Portmapper.
[X/OpenPCNFS] X/Open Company, Ltd., X/Open CAE Specification:
Protocols for X/Open Internetworking: (PC)NFS,
Developer's Specification, X/Open Company, Ltd.,
Apex Plaza, Forbury Road, Reading Berkshire, RG1
1AX, United Kingdom, 1991. This is an
indispensable reference for NFS version 2
protocol and accompanying protocols, including
the Lock Manager and the Portmapper.
8. Security Considerations
Since sensitive file data may be transmitted or received
from a server by the NFS protocol, authentication, privacy,
and data integrity issues should be addressed by implementations
of this protocol.
As with the previous protocol revision (version 2), NFS
version 3 defers to the authentication provisions of the
supporting RPC protocol [RFC1057], and assumes that data
privacy and integrity are provided by underlying transport
layers as available in each implementation of the protocol.
See section 4.4 for a discussion relating to file access
permissions.
9. Acknowledgements
This description of the protocol is derived from an original
document written by Brian Pawlowski and revised by Peter
Staubach. This protocol is the result of a co-operative
effort that comprises the contributions of Geoff Arnold,
Brent Callaghan, John Corbin, Fred Glover, Chet Juszczak,
Mike Eisler, John Gillono, Dave Hitz, Mike Kupfer, Rick
Macklem, Ron Minnich, Brian Pawlowski, David Robinson, Rusty
Sandberg, Craig Schamp, Spencer Shepler, Carl Smith, Mark
Stein, Peter Staubach, Tom Talpey, Rob Thurlow, and Mark
Wittle.
10. Authors' Addresses
Address comments related to this protocol to:
nfs3@eng.sun.com
Brent Callaghan
Sun Microsystems, Inc.
2550 Garcia Avenue
Mailstop UMTV05-44
Mountain View, CA 94043-1100
Phone: 1-415-336-1051
Fax: 1-415-336-6015
EMail: brent.callaghan@eng.sun.com
Brian Pawlowski
Network Appliance Corp.
319 North Bernardo Ave.
Mountain View, CA 94043
Phone: 1-415-428-5136
Fax: 1-415-428-5151
EMail: beepy@netapp.com
Peter Staubach
Sun Microsystems, Inc.
2550 Garcia Avenue
Mailstop UMTV05-44
Mountain View, CA 94043-1100
Phone: 1-415-336-5615
Fax: 1-415-336-6015
EMail: peter.staubach@eng.sun.com
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