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but is obsolete, mainly because it will fail in case this device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> [-nlfvr] dir |
device
where the <suffix> is filesystem type or a value from
"uhelper=" mtab option.
The uhelper (unprivileged umount request helper) is possible
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.