Name

mount, umount − mount and unmount a Network File System (NFS)

Syntax

/etc/mount [ −t nfs −f −r −v ] [ options ] device directory

/etc/umount [ −v ] directory

Description

The mount command allows you to mount a file system or directory onto a directory. Once a file system or directory has been mounted, it is treated as a file system.

The argument device can have one of the following forms:

host:remote_name

remote_name@host

The remote_name is the name of a file system or subtree of a file system that has been exported by host.  The file directory must exist and must be a directory.  It becomes the name of the newly mounted file system. 

General users can mount file systems with certain restrictions in addition to those listed in mount(.).

The umount command unmounts the remote file system that was previously mounted on the specified directory.

Options

See the mount() reference page for a description of the −t option. 

−fFast unmount.  The −f option has no meaning for local file systems and directories.  However, for remote file system types (such as NFS), the −f option causes the client to unmount the remotely mounted file systems and directories without notifying the server.  This can avoid the delay of waiting for acknowledgment from a server that is down. 

−rIndicates that the file system is to be mounted read only. 

−vTells what did or did not happen.  (Verbose flag)

−o optionsSpecifies options as a sequence of words, separated by commas, from the list that follows.  The default options are as follows: rw,hard,intr,retry=10,000,timeo=11,retrans=4, \
port=NFS_PORT,pgthresh=64 Defaults for rsize and wsize are set by the kernel.  The NFS options are as follows:

bgIf the first mount attempt fails, retry the mount in the background the number of times specified (the default is 10,000 times). 

hardRetry the NFS operation (not the mount) request until server responds.  The hard option applies after the mount has succeeded. Use the hard option when mounting rw (read-write) file systems.

intrAllow hard mounted file system operations to be interrupted. 

nintrDisallow hard mounted file system operations from being interrupted. 

noexecBinaries cannot be executed from this file system. 

nosuidThe setuid and setgid programs can not be executed from this file system.

pgthresh=##
Set the paging threshold for this file system in kilobytes.

port=nSet server IP port number to n. 

retrans=nSet number of NFS operation retransmissions (not the mount) to n.  The retrans= option applies after the mount has succeeded.

retry=nSet number of mount failure retries to n.  The retry= option applies to the mount command, itself.

roRead-only. 

rsize=nSet read buffer size to n bytes. 

rwRead/write. 

softReturn an error if the server does not respond to the NFS operation (not the mount) request.  The soft option applies after the mount has succeeded. Do not use the soft option to mount rw (read-write) file systems.

timeo=nSet NFS timeout to n tenths of a second. 

wsize=nSet write buffer size to n bytes. 

The following options affect how quickly you see updates to a file or directory that has been modified by another host.  Increasing these values will give you slightly better performance.  Decreasing these values decreases the time it takes for you to see modifications made on another host.  If you are the only modifier of files under this mount point, you can increase these values. 

acdirmin=nHold cached directory attributes for at least n seconds.  The default is 30 seconds. 

acdirmax=nHold cached directory attributes for no more than n seconds.  The default is 60 seconds.  The maximum value allowed is 3600. 

acregmin=nHold cached file attributes for at least n seconds.  The default is 3 seconds. 

acregmax=nHold cached file attributes for no more than n seconds.  The default is 60 seconds.  The maximum value allowed is 3600. 

actimeo=nSet all four attributes cache timeout values to n. 

noacDo not set attribute caching.  This is equivalent to actimeo=0. 

The bg option causes mount to run in the background if the server’s mountd daemon does not respond. The mount command attempts each request retry=n times before giving up.  Once the file system is mounted, each NFS request made in the kernel waits timeo=n tenths of a second for a response.  If no response arrives, the time-out is multiplied by 2 and the request is retransmitted. 

When retrans=n retransmissions have been sent with no reply, a soft mounted file system returns an error on the request and a hard mounted file system retries the request.  If a hard mounted file system was mounted with the intr option, an operation within that file system that is retrying (for example, the server is down) can be interrupted. File systems that are mounted rw (read-write) should use the hard option.  The number of bytes in a read or write request can be set with the rsize and wsize options. The values for rsize and wsize must be between 512 and 8192, and be a multiple of 512.

The option for umount is:

−vTells what did or did not happen.  (Verbose flag)

Restrictions

If the directory on which a file system is to be mounted is a symbolic link, the file system is mounted on the directory to which the symbolic link refers, rather than being mounted on top of the symbolic link itself. 

The /etc/nfs_mount and /etc/nfs_umount commands should only be invoked by the mount and umount commands. It is recommended that users (and superusers) do not invoke the nfs_mount and nfs_umount commands. An exception to this rule is the use of the nfs_umount −b command in the /etc/rc.local file. The nfs_umount −b command broadcasts a message informing NFS servers that this machine no longer has any NFS filesystems mounted. This is done in case the machine had crashed while it had NFS filesystems mounted. The servers use this information to clean up their rmtab tables. The nfssetup command automatically adds the nfs_umount −b line to the /etc/rc.local file on NFS client systems.

Examples

The mount command invokes nfs_mount to do its work. A sample mount command is:

# mount −t nfs −o hard,pgthresh=100 server:/usr /usr

To mount the remote file system /usr/src onto the local directory /mnt with 1k transfer size, type:

# mount −t nfs −o rsize=1024,wsize=1024 serv:/usr/src /mnt

To mount the remote directory /usr/src/code onto the local directory /usr/src, type:

# mount −t nfs serv:/usr/src/code /usr/src

To hard mount a remote file system called /usr/src onto the local directory /usr/src, type:

# mount −t nfs −o hard serv:/usr/src /usr/src

Files

/etc/fstab File system information file

/etc/nfs_mount NFS-specific mount program

/etc/nfs_umount NFS-specific unmount program

See Also

getmnt(2), mount(2), fstab(5), exports(5nfs), mount(8), umount(8), mountd(8nfs), rmtab(5nfs), nfssetup(8nfs)