mount(8nfs) mount(8nfs)
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 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
The command unmounts the remote file system that was previously mounted on the specified directory.
Options
See the reference page for a description of the -t option.
-f Fast 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.
-r Indicates that the file system is to be mounted read only.
-v Tells what did or did not happen. (Verbose flag)
-o options Specifies 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:
bg If the first mount attempt fails, retry the mount in the background the number of times specified (the default is
10,000 times).
hard Retry the NFS operation (not the mount) request until server responds. The hard option applies after the has
succeeded. Use the hard option when mounting (read-write) file systems.
intr Allow hard mounted file system operations to be interrupted.
nintr Disallow hard mounted file system operations from being interrupted.
noexec Binaries cannot be executed from this file system.
nosuid The and programs can not be executed from this file system.
pgthresh=## Set the paging threshold for this file system in kilobytes.
port=n Set server IP port number to n.
retrans=n Set number of NFS operation retransmissions (not the mount) to n. The retrans= option applies after the has suc-
ceeded.
retry=n Set number of mount failure retries to n. The retry= option applies to the command, itself.
ro Read-only.
rsize=n Set read buffer size to n bytes.
rw Read/write.
soft Return an error if the server does not respond to the NFS operation (not the mount) request. The soft option
applies after the has succeeded. Do not use the soft option to mount (read-write) file systems.
timeo=n Set NFS timeout to n tenths of a second.
wsize=n Set 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=n Hold cached directory attributes for at least n seconds. The default is 30 seconds.
acdirmax=n Hold cached directory attributes for no more than n seconds. The default is 60 seconds. The maximum value
allowed is 3600.
acregmin=n Hold cached file attributes for at least n seconds. The default is 3 seconds.
acregmax=n Hold cached file attributes for no more than n seconds. The default is 60 seconds. The maximum value allowed is
3600.
actimeo=n Set all four attributes cache timeout values to n.
noac Do not set attribute caching. This is equivalent to actimeo=0.
The option causes to run in the background if the server's daemon does not respond. The 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 option, an operation within that file system that is
retrying (for example, the server is down) can be interrupted. File systems that are mounted (read-write) should use the hard option. The
number of bytes in a read or write request can be set with the and options. The values for and must be between 512 and 8192, and be a mul-
tiple of 512.
The option for is:
-v Tells 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 sym-
bolic link refers, rather than being mounted on top of the symbolic link itself.
The and commands should only be invoked by the and commands. It is recommended that users (and superusers) do not invoke the and commands.
An exception to this rule is the use of the -b command in the file. The -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 tables. The command automatically adds the -b line to the file on NFS client systems.
Examples
The command invokes to do its work. A sample command is:
# mount -t nfs -o hard,pgthresh=100 server:/usr /usr
To mount the remote file system onto the local directory with 1k transfer size, type:
# mount -t nfs -o rsize=1024,wsize=1024 serv:/usr/src /mnt
To mount the remote directory onto the local directory type:
# mount -t nfs serv:/usr/src/code /usr/src
To hard mount a remote file system called onto the local directory type:
# mount -t nfs -o hard serv:/usr/src /usr/src
Files
File system information file
NFS-specific mount program
NFS-specific unmount program
See Also
getmnt(2), mount(2), fstab(5), exports(5nfs), mount(8), umount(8), mountd(8nfs), rmtab(5nfs), nfssetup(8nfs)
mount(8nfs)