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lives may also work, but is obsolete, mainly because it will fail in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
hierarchy now, and cleanup all references to the filesystem as
soon as it is not busy anymore. (Requires kernel 2.4.11 or
later.)
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 non-
root 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/.