NFS/トラブルシューティング
関連記事
よくある問題と解決法の記事。
サーバー側の問題
exportfs: /etc/exports:2: syntax error: bad option list
/etc/exports 内のオプションリストから空白を全て削除してください。
グループ/GID パーミッションの問題
If NFS shares mount fine, and are fully accessible to the owner, but not to group members; check the number of groups that user belongs to. NFS has a limit of 16 on the number of groups a user can belong to. If you have users with more than this, you need to enable the --manage-gids start-up flag for rpc.mountd on the NFS server.
/etc/conf.d/nfs-server.conf
# Options for rpc.mountd. # If you have a port-based firewall, you might want to set up # a fixed port here using the --port option. # See rpc.mountd(8) for more details. MOUNTD_OPTS="--manage-gids"
ファイルを書き込もうとしたときに "Permission denied"
- root で共有をマウントして、クライアントから完全に読み書きできるようにしたい場合、
/etc/exportsのエクスポートに no_root_squash オプションを追加してください:
/var/cache/pacman/pkg 192.168.1.0/24(rw,no_subtree_check,no_root_squash)
showmount -e コマンドを実行したときに "RPC: Program not registered"
サーバー側で nfs-server.service と rpcbind.service が実行していることを確認してください。systemd を参照。実行されてない場合、サービスを起動して有効化してください。
クライアント側の問題
mount.nfs4: No such device
nfs モジュールがロードされているか確認してください:
lsmod | grep nfs
上記コマンドで何も返ってこなかったり nfsd-stuff しか表示されない場合、次を実行:
# modprobe nfs
mount.nfs4: access denied by server while mounting
NFS shares have to reside in /srv - check your /etc/exports file and if necessary create the proper folder structure as described in the NFS#File_system page.
Check that the permissions on your client's folder are correct. Try using 755.
or try "exportfs -rav" reload /etc/exports file.
OS X クライアントから接続できない
When trying to connect from a OS X client, you will see that everything is ok at logs, but MacOS X refuses to mount your NFS share. You have to add insecure option to your share and re-run exportfs -r.
OS X クライアントからの接続が不安定
OS X の NFS クライアントは OS X サーバーに最適化されているため Linux サーバーでは複数の問題が存在します。パフォーマンスが出なかったり、頻繁に切断したり、日本語の文字に問題が起こる場合、デフォルトのマウントオプションを編集して Mac クライアントの /etc/nfs.conf に nfs.client.mount.options = intr,locallocks,nfc という行を追加してください。マウントオプションに関する詳細情報は こちら にあります。
巨大なファイルをコピーするときにクライアントが一時的にフリーズする
クライアントマシンから NFS サーバーに巨大なファイルをコピーする際、転送速度に非常に高速だと、数秒後に速度が落ちて、転送が完了するまで暫くの間、クライアントマシンが一時的にロックアップすることがあります。
クライアントの (/etc/fstab の) マウントオプションに sync を追加することで問題は解決します。
mount.nfs: Operation not permitted
nfs-utils 1.2.1-2 以上にアップデートすると、NFS 共有のマウントは機能を停止します。nfs-utils がデフォルトで NFSv3 ではなく NFSv4 を使うようになるからです。この問題はコマンドラインでマウントオプションとして 'vers=3' や 'nfsvers=3' を使うことで解決できます:
# mount.nfs remote target directory -o ...,vers=3,... # mount.nfs remote target directory -o ...,nfsvers=3,...
もしくは /etc/fstab でマウントする場合:
remote target directory nfs ...,vers=3,... 0 0 remote target directory nfs ...,nfsvers=3,... 0 0
mount.nfs: Protocol not supported
Check you are not mounting including the export root. Use:
# mount SERVER:/ /mnt
instead of, i.e.:
# mount SERVER:/srv/nfs4/ /mnt
Sometimes it could be the same problem with "Operation not permitted" : nfs-utils uses NFSv4 per default instead of NFSv3. Go and see the previons section
Vagrant と synced_folders の問題
Vagrant のスクリプトで NFS を通してフォルダをマウントできない場合、net-tools パッケージをインストールすることで問題は解決します。
パフォーマンスの問題
この NFS Howto ページ にパフォーマンスに関する有益な情報が載っています。以下はその他のヒントです:
問題の診断
- Htop should be your first port of call. The most obvious symptom will be a maxed-out CPU.
- Press F2, and under "Display options", enable "Detailed CPU time". Press F1 for an explanation of the colours used in the CPU bars. In particular, is the CPU spending most of its time responding to IRQs, or in Wait-IO (wio)?
サーバースレッド
Symptoms: Nothing seems to be very heavily loaded, but some operations on the client take a long time to complete for no apparent reason.
If your workload involves lots of small reads and writes (or if there are a lot of clients), there may not be enough threads running on the server to handle the quantity of queries. To check if this is the case, run the following command on one or more of the clients:
# nfsstat -rc
Client rpc stats: calls retrans authrefrsh 113482 0 113484
If the retrans column contains a number larger than 0, the server is failing to respond to some NFS requests, and the number of threads should be increased.
To increase the number of threads on the server, edit the file /etc/conf.d/nfs-server.conf and set the value in the NFSD_OPTS variable.
For example, to set the number of threads to 32:
/etc/conf.d/nfs-server.conf
NFSD_OPTS="32"
The default number of threads is 8. Try doubling this number until retrans remains consistently at zero. Don't be afraid of increasing the number quite substantially. 256 threads may be quite reasonable, depending on the workload. You will need to restart the NFS server daemon each time you modify the configuration file. Bear in mind that the client statistics will only be reset to zero when the client is rebooted.
Use htop (disable the hiding of kernel threads) to keep an eye on how much work each nfsd thread is doing. If you reach a point where the retrans values are non-zero, but you can see nfsd threads on the server doing no work, something different is now causing your bottleneck, and you'll need to re-diagnose this new problem.
Close-to-open/flush-on-close
Symptoms: Your clients are writing many small files. The server CPU is not maxed out, but there is very high wait-IO, and the server disk seems to be churning more than you might expect.
In order to ensure data consistency across clients, the NFS protocol requires that the client's cache is flushed (all data is pushed to the server) whenever a file is closed after writing. Because the server is not allowed to buffer disk writes (if it crashes, the client won't realise the data wasn't written properly), the data is written to disk immediately before the client's request is completed. When you're writing lots of small files from the client, this means that the server spends most of its time waiting for small files to be written to its disk, which can cause a significant reduction in throughput.
See this excellent article or the nfs manpage for more details on the close-to-open policy. There are several approaches to solving this problem:
nocto マウントオプション
Does your situation match these conditions?
- The export you have mounted on the client is only going to be used by the one client.
- It doesn't matter too much if a file written on one client doesn't immediately appear on other clients.
- It doesn't matter if after a client has written a file, and the client thinks the file has been saved, and then the client crashes, the file may be lost.
If you're happy with the above conditions, you can use the nocto mount option, which will disable the close-to-open behaviour. See the nfs manpage for details.
async エクスポートオプション
Does your situation match these conditions?
- It's important that when a file is closed after writing on one client, it is:
- Immediately visible on all the other clients.
- Safely stored on the server, even if the client crashes immediately after closing the file.
- It's not important to you that if the server crashes:
- You may loose the files that were most recently written by clients.
- When the server is restarted, the clients will believe their recent files exist, even though they were actually lost.
In this situation, you can use async instead of sync in the server's /etc/exports file for those specific exports. See the exports manual page for details. In this case, it does not make sense to use the nocto mount option on the client.
バッファキャッシュサイズと MTU
Symptoms: High kernel or IRQ CPU usage, a very high packet count through the network card.
This is a trickier optimisation. Make sure this is definitely the problem before spending too much time on this. The default values are usually fine for most situations.
See this excellent article for information about I/O buffering in NFS. Essentially, data is accumulated into buffers before being sent. The size of the buffer will affect the way data is transmitted over the network. The Maximum Transmission Unit (MTU) of the network equipment will also affect throughput, as the buffers need to be split into MTU-sized chunks before they're sent over the network. If your buffer size is too big, the kernel or hardware may spend too much time splitting it into MTU-sized chunks. If the buffer size is too small, there will be overhead involved in sending a very large number of small packets. You can use the rsize and wsize mount options on the client to alter the buffer cache size. To achieve the best throughput, you need to experiment and discover the best values for your setup.
It is possible to change the MTU of many network cards. If your clients are on a separate subnet (e.g. for a Beowulf cluster), it may be safe to configure all of the network cards to use a high MTU. This should be done in very-high-bandwidth environments.
rsize と wsize についての詳細は nfs の man ページを参照してください。
デバッグ
rpcdebug を使う
Using rpcdebug is the easiest way to manipulate the kernel interfaces in place of echoing bitmasks to /proc.
| オプション | 説明 |
|---|---|
| -c | Clear the given debug flags |
| -s | Set the given debug flags |
| -m module | Specify which module's flags to set or clear. |
| -v | Increase the verbosity of rpcdebug's output |
| -h | Print a help message and exit. When combined with the -v option, also prints the available debug flags. |
-m オプションでは、以下のモジュールが利用できます:
| モジュール | 説明 |
|---|---|
| nfsd | NFS サーバー |
| nfs | NFS クライアント |
| nlm | NFS クライアントあるいはサーバーの Network Lock Manager |
| rpc | NFS クライアントあるいはサーバーの Remote Procedure Call モジュール |
例:
rpcdebug -m rpc -s all # sets all debug flags for RPC rpcdebug -m rpc -c all # clears all debug flags for RPC rpcdebug -m nfsd -s all # sets all debug flags for NFS Server rpcdebug -m nfsd -c all # clears all debug flags for NFS Server
Once the flags are set you can tail the journal for the debug output, usually journalctl -fl or similar.
カーネルインターフェイス
A bitmask of the debug flags can be echoed into the interface to enable output to syslog; 0 is the default:
/proc/sys/sunrpc/nfsd_debug /proc/sys/sunrpc/nfs_debug /proc/sys/sunrpc/nlm_debug /proc/sys/sunrpc/rpc_debug
Sysctl controls are registered for these interfaces, so they can be used instead of echo:
sysctl -w sunrpc.rpc_debug=1023 sysctl -w sunrpc.rpc_debug=0 sysctl -w sunrpc.nfsd_debug=1023 sysctl -w sunrpc.nfsd_debug=0
At runtime the server holds information that can be examined:
grep . /proc/net/rpc/*/content cat /proc/fs/nfs/exports cat /proc/net/rpc/nfsd ls -l /proc/fs/nfsd
A rundown of /proc/net/rpc/nfsd (the userspace tool nfsstat pretty-prints this info):
* rc (reply cache): <hits> <misses> <nocache> - hits: client it's retransmitting - misses: a operation that requires caching - nocache: a operation that no requires caching * fh (filehandle): <stale> <total-lookups> <anonlookups> <dir-not-in-cache> <nodir-not-in-cache> - stale: file handle errors - total-lookups, anonlookups, dir-not-in-cache, nodir-not-in-cache . always seem to be zeros * io (input/output): <bytes-read> <bytes-written> - bytes-read: bytes read directly from disk - bytes-written: bytes written to disk * th (threads): <threads> <fullcnt> <10%-20%> <20%-30%> ... <90%-100%> <100%> - threads: number of nfsd threads - fullcnt: number of times that the last 10% of threads are busy - 10%-20%, 20%-30% ... 90%-100%: 10 numbers representing 10-20%, 20-30% to 100% . Counts the number of times a given interval are busy * ra (read-ahead): <cache-size> <10%> <20%> ... <100%> <not-found> - cache-size: always the double of number threads - 10%, 20% ... 100%: how deep it found what was looking for - not-found: not found in the read-ahead cache * net: <netcnt> <netudpcnt> <nettcpcnt> <nettcpconn> - netcnt: counts every read - netudpcnt: counts every UDP packet it receives - nettcpcnt: counts every time it receives data from a TCP connection - nettcpconn: count every TCP connection it receives * rpc: <rpccnt> <rpcbadfmt+rpcbadauth+rpcbadclnt> <rpcbadfmt> <rpcbadauth> <rpcbadclnt> - rpccnt: counts all rpc operations - rpcbadfmt: counts if while processing a RPC it encounters the following errors: . err_bad_dir, err_bad_rpc, err_bad_prog, err_bad_vers, err_bad_proc, err_bad - rpcbadauth: bad authentication . does not count if you try to mount from a machine that it's not in your exports file - rpcbadclnt: unused * procN (N = vers): <vs_nproc> <null> <getattr> <setattr> <lookup> <access> <readlink> <read> <write> <create> <mkdir> <symlink> <mknod> <remove> <rmdir> <rename> <link> <readdir> <readdirplus> <fsstat> <fsinfo> <pathconf> <commit> - vs_nproc: number of procedures for NFS version . v2: nfsproc.c, 18 . v3: nfs3proc.c, 22 - v4, nfs4proc.c, 2 - statistics: generated from NFS operations at runtime * proc4ops: <ops> <x..y> - ops: the definition of LAST_NFS4_OP, OP_RELEASE_LOCKOWNER = 39, plus 1 (so 40); defined in nfs4.h - x..y: the array of nfs_opcount up to LAST_NFS4_OP (nfsdstats.nfs4_opcount[i])
NFSD デバッグフラグ
/usr/include/linux/nfsd/debug.h
/* * knfsd debug flags */ #define NFSDDBG_SOCK 0x0001 #define NFSDDBG_FH 0x0002 #define NFSDDBG_EXPORT 0x0004 #define NFSDDBG_SVC 0x0008 #define NFSDDBG_PROC 0x0010 #define NFSDDBG_FILEOP 0x0020 #define NFSDDBG_AUTH 0x0040 #define NFSDDBG_REPCACHE 0x0080 #define NFSDDBG_XDR 0x0100 #define NFSDDBG_LOCKD 0x0200 #define NFSDDBG_ALL 0x7FFF #define NFSDDBG_NOCHANGE 0xFFFF
NFS デバッグフラグ
/usr/include/linux/nfs_fs.h
/* * NFS debug flags */ #define NFSDBG_VFS 0x0001 #define NFSDBG_DIRCACHE 0x0002 #define NFSDBG_LOOKUPCACHE 0x0004 #define NFSDBG_PAGECACHE 0x0008 #define NFSDBG_PROC 0x0010 #define NFSDBG_XDR 0x0020 #define NFSDBG_FILE 0x0040 #define NFSDBG_ROOT 0x0080 #define NFSDBG_CALLBACK 0x0100 #define NFSDBG_CLIENT 0x0200 #define NFSDBG_MOUNT 0x0400 #define NFSDBG_FSCACHE 0x0800 #define NFSDBG_PNFS 0x1000 #define NFSDBG_PNFS_LD 0x2000 #define NFSDBG_STATE 0x4000 #define NFSDBG_ALL 0xFFFF
NLM デバッグフラグ
/usr/include/linux/lockd/debug.h
/* * Debug flags */ #define NLMDBG_SVC 0x0001 #define NLMDBG_CLIENT 0x0002 #define NLMDBG_CLNTLOCK 0x0004 #define NLMDBG_SVCLOCK 0x0008 #define NLMDBG_MONITOR 0x0010 #define NLMDBG_CLNTSUBS 0x0020 #define NLMDBG_SVCSUBS 0x0040 #define NLMDBG_HOSTCACHE 0x0080 #define NLMDBG_XDR 0x0100 #define NLMDBG_ALL 0x7fff
RPC デバッグフラグ
/usr/include/linux/sunrpc/debug.h
/* * RPC debug facilities */ #define RPCDBG_XPRT 0x0001 #define RPCDBG_CALL 0x0002 #define RPCDBG_DEBUG 0x0004 #define RPCDBG_NFS 0x0008 #define RPCDBG_AUTH 0x0010 #define RPCDBG_BIND 0x0020 #define RPCDBG_SCHED 0x0040 #define RPCDBG_TRANS 0x0080 #define RPCDBG_SVCXPRT 0x0100 #define RPCDBG_SVCDSP 0x0200 #define RPCDBG_MISC 0x0400 #define RPCDBG_CACHE 0x0800 #define RPCDBG_ALL 0x7fff
一般注記事項
- While the number of threads can be increased at runtime via an echo to
/proc/fs/nfsd/threads, the cache size (double the threads, see the ra line of /proc/net/rpc/nfsd) is not dynamic. The NFS daemon must be restarted with the new thread size during initialization in order for the thread cache to properly adjust.
参照
- https://github.com/torvalds/linux/tree/master/include/linux
- http://linux.die.net/man/8/rpcdebug
- http://utcc.utoronto.ca/~cks/space/blog/linux/NFSClientDebuggingBits
- http://www.novell.com/support/kb/doc.php?id=7011571
- http://stromberg.dnsalias.org/~strombrg/NFS-troubleshooting-2.html
- http://www.opensubscriber.com/message/nfs@lists.sourceforge.net/7833588.html
他の問題
パーミッションの問題
If you find that you cannot set the permissions on files properly, make sure the user/group you are chowning are on both the client and server.
If all your files are owned by nobody, and you are using NFSv4, on both the client and server, you should:
- For systemd, ensure that the
nfs-idmapdservice has been started. - For initscripts, ensure that
NEED_IDMAPDis set toYESin/etc/conf.d/nfs-common.conf.
On some systems detecting the domain from FQDN minus hostname does not seem to work reliably. If files are still showing as nobody after the above changes, edit /etc/idmapd.conf, ensure that Domain is set to FQDN minus hostname. For example:
/etc/idmapd.conf
[General] Verbosity = 7 Pipefs-Directory = /var/lib/nfs/rpc_pipefs Domain = yourdomain.local [Mapping] Nobody-User = nobody Nobody-Group = nobody [Translation] Method = nsswitch
If nfs-idmapd.service refuses to start because it cannot open the Pipefs-directory (defined in /etc/idmapd.conf and appended with '/nfs'), issue a mkdir-command and restart the daemon.