Manual Pages for UNIX Darwin command on man mount

Manual Pages for UNIX Darwin command on man mount_nfs

MOUNTNFS(8) BSD System Manager's Manual MOUNTNFS(8)

NAME

mmoouunnttnnffss - mount NFS file systems

SYNOPSIS

mmoouunnttnnffss [-oo options] server:/path directory

DESCRIPTION

The mmoouunnttnnffss command calls the mount(2) system call to prepare and graft a remote NFS file system ( server:/path ) on to the file system tree at the point directory. This command is expected to be executed by the mount(8) command. Direct use of mmoouunnttnnffss to mount NFS file systems is strongly discouraged because there is little practical benefit of using it instead of mount(8). For NFS versions that use a separate mount protocol, mmoouunnttnnffss implements the mount protocol as described in RFC 1094, Appendix A and NFS: Network File System Version 3 Protocol Specification, RFC 1813, Appendix I. By default, mmoouunnttnnffss will attempt the mount twice before exiting with an

error. If the -oo bbgg option is given, it will attempt the mount once and

then background itself to continue trying another 10,000 times (pausing

for one minute between attempts). The option -oo rreettrryyccnntt= can be

used if a different retry behavior is desired for a mount. If the server becomes unresponsive while an NFS file system is mounted, any new or outstanding file operations on that file system will hang uninterruptibly until the server comes back (or that NFS file system is

forcibly unmounted). To modify this default behaviour, see the -oo iinnttrr

and -oo ssoofftt mount options.

Mount options are specified with a -oo flag followed by a comma separated

string of options. See the mount(8) man page for possible options and

their meanings. The following NFS-specific options are also available:

bbgg Retry mount in background. If an initial attempt to contact the server fails, fork off a child to keep trying the mount in the background. Useful for fstab(5), where the file system mount is not critical to multiuser operation. rreettrryyccnntt= Set the retry count for doing the mount to the specified value. The default is 1 for foreground mounts and 10,000 for background mounts. uuddpp Use UDP transport protocol. ttccpp Use the TCP transport protocol instead of UDP. The default is to

try TCP first, then fall back to UDP if the server doesn't sup-

port TCP. pprroottoo= Use the given transport protocol. Valid values are ttccpp and uuddpp. mmnnttuuddpp Force the mount protocol to use UDP transport, even for TCP NFS mounts. (Necessary for some old BSD servers.)

mmoouunnttppoorrtt=

Connect to the NFS server's mount daemon using the given port number.

ppoorrtt=

Connect to an NFS server at the given port number. nnooccoonnnn Do not connect UDP sockets. For UDP mount points, do not do a connect(2). This must be used for servers that do not reply to requests from the standard NFS port number 2049. It may also be required for servers with more than one IP address if replies come from an address other than the one specified in the requests. rreessvvppoorrtt Use a reserved socket port number. This is useful for mounting servers that require clients to use a reserved port number on the mistaken belief that this makes NFS more secure. (For the rare

case where the client has a trusted root account but untrustwor-

thy users and the network cables are in secure areas this does help, but for normal desktop clients this does not apply.) iinnttrr Make the mount interruptible, which implies that file system calls that are delayed due to an unresponsive server will fail with EINTR when a termination signal is posted for the process. ssoofftt Make the mount soft, which means that file system calls will fail after rreettrraannss round trip timeout intervals. Note: mounts which

are both soft and read-only will also have the llooccaalllloocckkss mount

option enabled by default - unless explicitly overridden with a

lock option (for example, nnoolloocckkss or nnoollooccaalllloocckkss ). vveerrss= nnffssvveerrss=

Set the NFS protocol version number - 2 for NFSv2, 3 for NFSv3

and 4 for NFSv4. The default is to try version 3 first, and fall back to version 2 if the mount fails. nnffssvv22 nnffssvv33

nnffssvv44 Deprecated. Use -oo vveerrss= to specify NFS protocol version.

sseecc= Force a specific security mechanism to be used for the mount, where mechanism is one of: krb5p, krb5i, krb5, or sys. When this option is not given the security mechanism will be negotiated transparently with the remote server. rrssiizzee= Set the read data size to the specified value. The default is 8192 for UDP mounts and 32768 for TCP mounts. It should normally be a power of 2 greater than or equal to 1024. Values greater than 4096 should be multiples of 4096. It may need to be lowered for UDP mounts when the ``fragments dropped due to timeout'' value is getting large while actively using a mount point. (Use

netstat(1) with the -ss option to see what the ``fragments dropped

due to timeout'' value is.) wwssiizzee=

Set the write data size to the specified value. Ditto the com-

ments w.r.t. the rrssiizzee option, but using the ``fragments dropped due to timeout'' value on the server instead of the client. Note that both the rrssiizzee and wwssiizzee options should only be used as a last ditch effort at improving performance when mounting servers that do not support TCP mounts. rrwwssiizzee= Set both the read data size and write data size to the specified value. ddssiizzee= Set the directory read size to the specified value. The value should normally be a multiple of DIRBLKSIZ that is <= the read size for the mount. rreeaaddaahheeaadd=

Set the maximum read-ahead count to the specified value. The

default is 4. This may be in the range of 0 - 16, and determines

how many blocks will be read ahead when a large file is being read sequentially. Trying larger values for this is suggested for mounts with a large bandwidth * delay product. rrddiirrpplluuss Used with NFS v3/v4 to specify that directory read operations should retrieve additional info about each entry (e.g. use the NFSv3 RReeaaddddiirrPPlluuss RPC). This option reduces RPC traffic for

cases such as ``ls -l'', but tends to flood the attribute and

name caches with prefetched entries. Try this option and see whether performance improves or degrades. Probably most useful for client to server network interconnects with a large bandwidth times delay product. aaccrreeggmmiinn= aaccrreeggmmaaxx= aaccddiirrmmiinn= aaccddiirrmmaaxx=

These options set the minimum and maximum attribute cache time-

outs for directories and "regular" (non-directory) files. The

default minimum is 5 seconds and the default maximum is 60 sec-

onds. Setting both the minimum and maximum to zero will disable attribute caching. The algorithm to calculate the timeout is based on the age of the file or directory. The older it is, the longer the attribute cache is considered valid, subject to the limits above. Note that the effectiveness of this algorithm

depends on how well the clocks on the client and server are syn-

chronized. aaccttiimmeeoo= Set all attribute cache timeouts to the same value. nnooaacc Disable attribute caching. Equivalent to setting aaccttiimmeeoo to 0. nnoonneeggnnaammeeccaacchhee Disable negative name caching. llooccaalllloocckkss Perform all file locking operations locally on the NFS client

instead of on the NFS server. This option can provide file lock-

ing support on an NFS file system for which the server does not support file locking. However, because the file locking is only performed on the client, the NFS server and other NFS clients will have no knowledge of the locks. Note: mounts which are both

soft and read-only will also have the llooccaalllloocckkss mount option

enabled by default - unless explicitly overridden with a lock

option (for example, nnoolloocckkss or nnoollooccaalllloocckkss ). nnoolloocckkss nnoolloocckkdd nnoolloocckk

nnoonnllmm Do not support NFS file locking operations. Any attempt to per-

form file locking operations on this mount will return the error ENOTSUP regardless of whether or not the NFS server supports NFS file locking. mmaaxxggrroouuppss= Set the maximum size of the group list for the credentials to the specified value. This should be used for mounts on old servers that cannot handle a group list size of 16, as specified in RFC 1057. Try 8, if users in a lot of groups cannot get a response from the mount point. dduummbbttiimmeerr Turn off the dynamic retransmit timeout estimator. This may be useful for UDP mounts that exhibit high retry rates, since it is possible that the dynamically estimated timeout interval is too short. ttiimmeeoo= Set the initial retransmit timeout to the specified value. May be useful for fine tuning UDP mounts over internetworks with high packet loss rates or an overloaded server. Try increasing the interval if nfsstat(1) shows high retransmit rates while the file

system is active or reducing the value if there is a low retrans-

mit rate but long response delay observed. (Normally, the dduummbbttiimmeerr option should be specified when using this option to manually tune the timeout interval.) rreettrraannss= Set the retransmit timeout count for soft mounts to the specified value. aassyynncc Assume that unstable write requests have actually been committed to stable storage on the server, and thus will not require resending in the event that the server crashes. Use of this option may improve performance but only at the risk of data loss

if the server crashes. Note: this mount option will only be hon-

ored if the nnffss..cclliieenntt..aalllloowwaassyynncc option in nfs.conf(5) is also enabled.

ssyynncc Perform I/O requests (specifically, write requests) syn-

chronously. The operation will not return until a response is received from the server. (The default, nnoossyynncc, behavior is to return once the I/O has been queued up.)

nfs.conf(5) can be used to configure some NFS client options. In partic-

ular, nnffss..cclliieenntt..mmoouunntt..ooppttiioonnss can be used to specify default mount

options. This can be useful in situations where it is not easy to con-

figure the command-line options. Some NFS client options in nfs.conf(5)

correspond to kernel configuration values which will get set by mmoouunnttnnffss when performing a mount. To update these values without performing a mount, use the command: mmoouunnttnnffss ccoonnffiigguuppddaattee. CCOOMMPPAATTIIBBIILLIITTYY

The following mmoouunnttnnffss command line flags have equivalent -oo option

forms (shown in parentheses) and their use is highly discouraged. The -oo

option forms should be used instead.

-22 (vers=2), -33 (vers=3), -44 (vers=4), -LL (nolocks), -PP (resvport), -TT

(tcp), -UU (mntudp), -bb (bg), -cc (noconn), -dd (dumbtimer), -ii (intr), -ll

(rdirplus), -ss (soft), -II readdirsize (dsize=#), -RR retrycnt

(retrycnt=#), -aa maxreadahead (readahead=#), -gg maxgroups (maxgroups=#),

-rr readsize (rsize=#), -tt timeout (timeo=#), -ww writesize (wsize=#), -xx

retrans (retrans=#).

EEXXAAMMPPLLEESS The simplest way to invoke mmoouunnttnnffss is with a command like: mmoouunntt rreemmootteehhoosstt:://ffiilleessyysstteemm //llooccaallmmoouunnttppooiinntt or:

mmoouunntt -tt nnffss rreemmootteehhoosstt:://ffiilleessyysstteemm //llooccaallmmoouunnttppooiinntt

It is also possible to automatically mount file systems at boot from your /etc/fstab by using a line like: remotehost:/home /home nfs rw 0 0 PPEERRFFOORRMMAANNCCEE As can be derived from the comments accompanying the options, performance

tuning of NFS can be a non-trivial task. Here are some common points to

watch: ++oo Use of the ssyynncc option will probably have a detrimental affect on

performance. Its use is discouraged as it provides little bene-

fit. ++oo Use of the aassyynncc option may improve performance, but only at the risk of losing data if the server crashes because the client will not be making sure that all data is committed to stable storage on the server. ++oo Increasing the read and write size with the rrssiizzee and wwssiizzee options respectively will increase throughput if the network interface can handle the larger packet sizes. The default read and write sizes are 8K when using UDP, and 32K when using TCP. Values over 16K are only supported for TCP, where 60K is the maximum. Any value over 32K is unlikely to get you more performance, unless you have a very fast network. ++oo If the network interface cannot handle larger packet sizes or a long train of back to back packets, you may see low performance figures or even temporary hangups during NFS activity. This can especially happen with lossy network connections (e.g. wireless networks) which can lead to a lot of dropped packets. In this case, decreasing the read and write size, using TCP, or a combination of both will usually lead to better throughput.

++oo For connections that are not on the same LAN, and/or may experi-

ence packet loss, using TCP is strongly recommended. EERRRROORRSS Some common problems with mmoouunnttnnffss can be difficult for first time users to understand. mountnfs: can't access /foo: Permission denied This message means that the remote host is either not exporting the file system you requested or is not exporting it to your host. If you believe the remote host is indeed exporting a file system to you, make sure the exports(5) file is exporting the proper directories. The program showmount(8) can be used to see a server's exports list. The command

``showmount -e remotehostname'' will display what file systems the remote

host is exporting. A common mistake is that mountd(8) will not export a file system with the

-aallllddiirrss option, unless it is a mount point on the exporting host. It is

not possible to remotely mount a subdirectory of an exported mount,

unless it is exported with the -aallllddiirrss option.

The following error: NFS Portmap: RPC: Program not registered means that the remote host is not running mountd(8). The program rpcinfo(8) can be used to determine if the remote host is running nfsd, and mountd by issuing the command:

rpcinfo -p remotehostname

If the remote host is running nfsd, mountd, rpc.statd, and rpc.lockd it would display: program vers proto port 100000 2 tcp 111 portmapper 100000 2 udp 111 portmapper 100005 1 udp 950 mountd 100005 3 udp 950 mountd 100005 1 tcp 884 mountd 100005 3 tcp 884 mountd 100003 2 udp 2049 nfs 100003 3 udp 2049 nfs 100003 2 tcp 2049 nfs 100003 3 tcp 2049 nfs 100024 1 udp 644 status 100024 1 tcp 918 status 100021 0 udp 630 nlockmgr 100021 1 udp 630 nlockmgr 100021 3 udp 630 nlockmgr 100021 4 udp 630 nlockmgr 100021 0 tcp 917 nlockmgr 100021 1 tcp 917 nlockmgr 100021 3 tcp 917 nlockmgr 100021 4 tcp 917 nlockmgr The error: mountnfs: can't get net id for host indicates that mmoouunnttnnffss cannot resolve the name of the remote host.