UMOUNT(8) System Administration UMOUNT(8)NAMEumount - unmount file systems
SYNOPSISumount [-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lives may also work, but is obsolete, mainly because it will fail in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-a, --all
All of the file systems described in /etc/mtab are unmounted.
(With umount version 2.7 and later: the proc filesystem is not
unmounted.)
-c, --no-canonicalize
Do not canonicalize paths. For more details about this option
see the mount(8) man page.
-d, --detach-loop
In case the unmounted device was a loop device, also free this
loop device.
--fake Causes everything to be done except for the actual system call;
this 'fakes' unmounting the filesystem. It can be used to
remove entries from /etc/mtab that were unmounted earlier with
the -n option.
-f, --force
Force unmount (in case of an unreachable NFS system). (Requires
kernel 2.1.116 or later.)
-i, --internal-only
Do not call the /sbin/umount.<filesystem> helper even if it
exists. By default /sbin/umount.<filesystem> helper is called
if one exists.
-n, --no-mtab
Unmount without writing in /etc/mtab.
-l, --lazy
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.)
-O, --test-opts options,list
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.
-r, --read-only
In case unmounting fails, try to remount read-only.
-t, --types vfstype,ext2,ext3
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 pre‐
fixed with no to specify the file system types on which no
action should be taken.
-v, --verbose
Verbose mode.
-h, --help
Print help message and exit.
-V, --version
Print version and exit.
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] [-t type.subtype]
where the <suffix> is filesystem type or a value from "uhelper=" or
"helper=" mtab option. The -t option is used for filesystems with sub‐
types support (for example /sbin/mount.fuse -t fuse.sshfs).
The uhelper= (unprivileged umount helper) is possible to use when non-
root user wants to umount a mountpoint which is not defined in the
/etc/fstab file (e.g. devices mounted by udisk).
The helper= mount option redirects all umount requests to the
/sbin/umount.<helper> independently on UID.
FILES
/etc/mtab table of mounted file systems
ENVIRONMENT
LIBMOUNT_FSTAB=<path>
overrides the default location of the fstab file
LIBMOUNT_MTAB=<path>
overrides the default location of the mtab file
LIBMOUNT_DEBUG=0xffff
enables debug output
SEE ALSOumount(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 package and is available
from Linux Kernel Archive ⟨ftp://ftp.kernel.org/pub/linux/utils/util-
linux/⟩.
util-linux August 2012 UMOUNT(8)
