UMOUNT(8)
NAME
umount - unmount file systems
SYNOPSIS
umount [-hV] umount -a [-dflnrv] [-t vfstype] [-O options] umount [-dflnrv] {dir|device}...
DESCRIPTION
The umount command detaches the file system(s) mentioned from the file
hierarchy. A file system is specified by giving the directory where it
has been mounted. Giving the special device on which the file system
lives may also work, but is obsolete, mainly because it will fail in
case this device was mounted on more than one directory.
Note that a file system cannot be unmounted when it is `busy' - for
example, when there are open files on it, or when some process has its
working directory there, or when a swap file on it is in use. The
offending process could even be umount itself - it opens libc, and libc
in its turn may open for example locale files. A lazy unmount avoids
this problem.
Options for the umount command:
-V Print version and exit.
-h Print help message and exit.
-v Verbose mode.
-n Unmount without writing in /etc/mtab.
-r In case unmounting fails, try to remount read-only.
- -d In case the unmounted device was a loop device, also free this
- loop device.
- -i Don't call the /sbin/umount.<filesystem> helper even if it
- exists. By default /sbin/umount.<filesystem> helper is called if one exists.
- -a All of the file systems described in /etc/mtab are unmounted.
- (With umount version 2.7 and later: the proc filesystem is not unmounted.)
- -t vfstype
- Indicate that the actions should only be taken on file systems of the specified type. More than one type may be specified in a comma separated list. The list of file system types can be prefixed with no to specify the file system types on which no action should be taken.
- -O options
- Indicate that the actions should only be taken on file systems with the specified options in /etc/fstab. More than one option type may be specified in a comma separated list. Each option can be prefixed with no to specify options for which no action should be taken.
- -f Force unmount (in case of an unreachable NFS system). (Requires
- kernel 2.1.116 or later.)
- -l Lazy unmount. Detach the filesystem from the filesystem hierar
- chy now, and cleanup all references to the filesystem as soon as it is not busy anymore. (Requires kernel 2.4.11 or later.)
- --no-canonicalize
- Don't canonicalize paths. For more details about this option see the mount(8) man page.
THE LOOP DEVICE
The umount command will free the loop device (if any) associated with
the mount, in case it finds the option `loop=...' in /etc/mtab, or when
the -d option was given. Any pending loop devices can be freed using
`losetup -d', see losetup(8).
NOTES
The syntax of external umount helpers is:
/sbin/umount.<suffix> {dir|device} [-nlfvr]
where the <suffix> is filesystem type or a value from "uhelper=" mtab
option.
The uhelper (unprivileged umount helper) is possible to used when nonroot user wants to umount a mountpoint which is not defined in the
/etc/fstab file (e.g devices mounted by HAL).
FILES
/etc/mtab table of mounted file systems
SEE ALSO
umount(2), mount(8), losetup(8).
HISTORY
A umount command appeared in Version 6 AT&T UNIX.
AVAILABILITY
- The umount command is part of the util-linux-ng package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.