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Manual page for MOUNT(8)

mount, umount - mount and dismount filesystems

SYNOPSIS

/usr/etc/mount [ -p ]
/usr/etc/mount -a [ vd [ f | n ]] [ -t type ]
/usr/etc/mount [ -rvd [ f | n ]] [ -t type ] [ -o options ] fsname dir
/usr/etc/mount [ -vd [ f | n ]] [ -o options ] fsname | dir

/usr/etc/umount [ -t type ] [ -h host ]
/usr/etc/umount -a[v]
/usr/etc/umount [ -v ] fsname | dir

DESCRIPTION

The mount command attaches a filesystem fsname to the file tree at the directory dir. The directory dir may or may not already exist. If dir already exists, its contents are hidden until the filesystem is unmounted, and dir becomes the name of the newly mounted root. If fsname is of the form host:path the filesystem type is assumed to be nfs.

The umount command detaches the filesystem fsname previously mounted on directory dir. Either the filesystem name or the mounted-on directory may be used.

The mount and umount commands maintain a table of mounted filesystems in /etc/mtab, described in mtab.5 The mount command mounts entries onto the filesystem from data it finds in one of two places. If NetInfo is running, it comes from netinfo.5 Otherwise, the entries are stored in /etc/fstab.5 Note that boot time mounts of type "4.3" filesystems always occur before NetInfo is running, and so must be stored in /etc/fstab to be seen by the system. If invoked without an argument, mount displays the table from /etc/mtab. If invoked with only one of fsname or dir mount searches the filesystem table for an entry whose dir or fsname field matches the given argument. For example, if this line is in /etc/fstab:

: /dev/sd1a /usr 4.3 rw 1 1

then the commands mount /usr and mount /dev/sd1a are short for mount /dev/sd1a /usr

MOUNT OPTIONS

-p: Print the list of mounted filesystems in a format suitable for use in /etc/fstab.
-a: Attempt to mount all the filesystems described in the filesystem table. (In this case, fsname and dir are taken from the filesystem table.) If a type is specified all of the filesystems in the filesystem table with that type are mounted. Filesystems are not necessarily mounted in the order listed in the table.
-f: Fake a new /etc/mtab entry, but do not actually mount any filesystems.
-n: Mount the filesystems without updating /etc/mtab. (This can be useful for recovering from an overly full disk.)
-v: Verbose -- mount displays a message indicating the filesystem being mounted.
-d: Don't check if NFS mount appears to be mounting a directory on top of itself. Otherwise, mount ignores such requests. Since the NFS daemon on a machine might not have the same filesystem root as the mount process, this option may be necessary in a chroot'ed environment.
-t: The next argument is the filesystem type. The accepted types are 4.3, nfs, dos, macintosh, and cfs (CD-ROM file system). See fstab.5 for a description of these filesystem types.
-r: Mount the specified filesystem read-only. This is short for:

: mount -o ro fsname dir

: Physically write-protected and magnetic tape filesystems must be mounted read-only, or errors occur when access times are updated whether or not any explicit write is attempted.
-o: Specify options, a list of comma-separated words from the list below. Some options are valid for all filesystem types, while others apply to a specific type only.
: The following is a list of options valid on all file systems (the default is rw,suid if the filesystem is mounted by root and rw,nosuid if the filesystem is not mounted by root):

rw: read/write.
ro: read-only.
suid: set-uid execution allowed (cannot be specified; default if root mounts the filesystem).
nosuid: set-uid execution not allowed.
noauto: do not mount this file system automatically (mount -a).
remount: change the mount options on this file system without unmounting it first.

: options specific to nfs (NFS) file systems. The defaults are:
fg,mnttimeo=20,retry=1,timeo=7,retrans=3,port=NFS_PORT,hard
The defaults for rsize and wsize set by the kernel.

bg: if the first mount attempt fails, retry in the background.
fg: retry in foreground.
mnttimeo=n: set mount timeout to n seconds.
retry=n: set number times to retry mount to n.
rsize=n: set read buffer size to n bytes.
wsize=n: set write buffer size to n bytes.
timeo=n: set NFS timeout to n tenths of a second.
retrans=n: set number of NFS retransmissions to n.
port=n: set server IP port number to n.
soft: return error if server doesn't respond. Do not use this option with the rw option.
hard: retry request until server responds.
intr: allow keyboard interrupts on hard mounts.
net: Tell the NFS automounter to recognize this as a "network" mount. The mount command will ignore these entries and allow the autonfsmount(8) to take care of them. This option allows one to create a uniform view of the network from all machines. Typically, the mount point specified is "/Net". A mount of the form "mount -o net MACHINE:PATH /Net" translates to "mount MACHINE:PATH /Net/MACHINE/PATH". If the mount is performed on the machine serving the file system, then no actual mount occurs. Instead, a symbolic link is created from "/Net/MACHINE" to "/".
acregmin=n: set minimum time interval (in seconds) for file entry caching
acregmax=n: set maximum time interval (in seconds) for file entry caching
acdirmin=n: set minimum time interval for directory entry caching
acdirmax=n: set maximum time interval for directory entry caching
noac: set no file attribute caching

: The bg option causes mount to run in the background if the server's mountd.8 does not respond. mount attempts each request retry=n times before giving up. Once the filesystem 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 filesystem returns an error on the request and a hard mounted filesystem prints a message and retries the request. Filesystems that are mounted rw (read-write) should use the hard option. The intr option allows keyboard interrupts to kill a process that is hung waiting for a response on a hard mounted filesystem. The number of bytes in a read or write request can be set with the rsize and wsize options.

The attribute caching options can be used to defeat or modify client-side caching of attributes relating to objects accessed via NFS from a server. Changing these options can have a severe impact on the client-side performance of an NFS filesystem. A typical scenario where changing the parameters is beneficial is a multi-workstation development environment, where multiple clients are performing read/write file access to a common source file set.

UMOUNT OPTIONS

-h host: Unmount all filesystems listed in /etc/mtab that are remote-mounted from host.
-a: Attempt to unmount all the filesystems currently mounted (listed in /etc/mtab). In this case, fsname is taken from /etc/mtab.
-v: Verbose -- umount displays a message indicating the filesystem being unmounted.

EXAMPLES

mount /dev/sd1a /usr            	mount a local disk
mount -ft 4.3 /dev/nd0 /       	fake an entry for nd root
mount -at 4.3                  	mount all 4.3 filesystems
mount -t nfs serv:/usr/src /usr/src	mount remote filesystem
mount serv:/usr/src /usr/src    	same as above
mount -o hard serv:/usr/src /usr/src	same as above but hard mount
mount -p > /etc/fstab          	save current mount state

FILES

/etc/mtab table of mounted filesystems
/etc/fstab table of filesystems mounted at boot

BUGS

Mounting filesystems full of garbage crashes the system.

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