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umount - Unix, Linux Command
umount - unmount file systems
umount -a [-dflnrv] [-t vfstype] [-O options]
umount [-dflnrv] dir | device [...]
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may also work, but is obsolete, mainly because it will fail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
A lazy unmount avoids this problem.
Options for the
Print version and exit.
Print help message and exit.
Unmount without writing in
In case unmounting fails, try to remount read-only.
In case the unmounted device was a loop device, also
free this loop device.
Dont call the /sbin/umount.<filesystem> helper even if it exists. By default /sbin/umount.<filesystem> helper is called if one exists.
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.
Force unmount (in case of an unreachable NFS system).
(Requires kernel 2.1.116 or later.)
Lazy unmount. Detach the filesystem from the filesystem hierarchy now,
and cleanup all references to the filesystem as soon as it is not busy
(Requires kernel 2.4.11 or later.)
THE LOOP DEVICE
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
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).
/etc/mtab table of mounted file systems
umount command appeared in Version 6 AT&T UNIX.