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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | LOOP DEVICE | EXTERNAL HELPERS | FILES | ENVIRONMENT | SEE ALSO | HISTORY | AVAILABILITY | COLOPHON |
UMOUNT(8) System Administration UMOUNT(8)
umount - unmount file systems
umount -a [-dflnrv] [-t fstype] [-O option...]
umount [-dflnrv] {directory|device}...
umount -h|-V
The umount command detaches the mentioned file system(s) 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file system lives may also work, but is obsolete, mainly because it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.
-a, --all
All of the filesystems described in /proc/self/mountinfo (or
in deprecated /etc/mtab) are unmounted, except the proc,
devfs, devpts, sysfs, rpc_pipefs and nfsd filesystems. This
list of the filesystems may be replaced by --types umount
option.
-A, --all-targets
Unmount all mountpoints in the current namespace for the
specified filesystem. The filesystem can be specified by one
of the mountpoints or the device name (or UUID, etc.). When
this option is used together with --recursive, then all nested
mounts within the filesystem are recursively unmounted. This
option is only supported on systems where /etc/mtab is a
symlink to /proc/mounts.
-c, --no-canonicalize
Do not canonicalize paths. The paths canonicalization is
based on stat(2) and readlink(2) system calls. These system
calls may hang in some cases (for example on NFS if server is
not available). The option has to be used with canonical path
to the mount point.
For more details about this option see the mount(8) man page.
Note that umount does not pass this option to the
/sbin/umount.type helpers.
-d, --detach-loop
When the unmounted device was a loop device, also free this
loop device. This option is unnecessary for devices
initialized by mount(8), in this case "autoclear"
functionality is enabled by default.
--fake Causes everything to be done except for the actual system call
or umount helper execution; this 'fakes' unmounting the
filesystem. It can be used to remove entries from the
deprecated /etc/mtab that were unmounted earlier with the -n
option.
-f, --force
Force an unmount (in case of an unreachable NFS system).
Note that this option does not guarantee that umount command
does not hang. It's strongly recommended to use absolute
paths without symlinks to avoid unwanted readlink and stat
system calls on unreachable NFS in umount.
-i, --internal-only
Do not call the /sbin/umount.filesystem helper even if it
exists. By default such a helper program is called if it
exists.
-l, --lazy
Lazy unmount. Detach the filesystem from the file hierarchy
now, and clean up all references to this filesystem as soon as
it is not busy anymore.
-n, --no-mtab
Unmount without writing in /etc/mtab.
-O, --test-opts option...
Unmount only the filesystems that have the specified option
set in /etc/fstab. More than one option may be specified in a
comma-separated list. Each option can be prefixed with no to
indicate that no action should be taken for this option.
-R, --recursive
Recursively unmount each specified directory. Recursion for
each directory will stop if any unmount operation in the chain
fails for any reason. The relationship between mountpoints is
determined by /proc/self/mountinfo entries. The filesystem
must be specified by mountpoint path; a recursive unmount by
device name (or UUID) is unsupported.
-r, --read-only
When an unmount fails, try to remount the filesystem read-
only.
-t, --types type...
Indicate that the actions should only be taken on filesystems
of the specified type. More than one type may be specified in
a comma-separated list. The list of filesystem types can be
prefixed with no to indicate that no action should be taken
for all of the mentioned types. Note that umount reads
information about mounted filesystems from kernel
(/proc/mounts) and filesystem names may be different than
filesystem names used in the /etc/fstab (e.g. "nfs4" vs.
"nfs").
-v, --verbose
Verbose mode.
-V, --version
Display version information and exit.
-h, --help
Display help text and exit.
The umount command will automatically detach loop device previously
initialized by mount(8) command independently of /etc/mtab.
In this case the device is initialized with "autoclear" flag (see
losetup(8) output for more details), otherwise it's necessary to use
the option --detach-loop or call losetup -d <device>. The autoclear
feature is supported since Linux 2.6.25.
The syntax of external unmount helpers is:
umount.suffix {directory|device} [-flnrv] [-t type.subtype]
where suffix is the filesystem type (or the value from a uhelper= or
helper= marker in the mtab file). The -t option can be used for
filesystems that have subtype support. For example:
umount.fuse -t fuse.sshfs
A uhelper=something marker (unprivileged helper) can appear in the
/etc/mtab file when ordinary users need to be able to unmount a
mountpoint that is not defined in /etc/fstab (for example for a
device that was mounted by udisks(1)).
A helper=type marker in the mtab file will redirect all unmount
requests to the /sbin/umount.type helper independently of UID.
Note that /etc/mtab is currently deprecated and helper= and another
userspace mount options are maintained by libmount.
/etc/mtab
table of mounted filesystems (deprecated and usually replaced
by symlink to /proc/mounts)
/etc/fstab
table of known filesystems
/proc/self/mountinfo
table of mounted filesystems generated by kernel.
LIBMOUNT_FSTAB=<path>
overrides the default location of the fstab file (ignored for
suid)
LIBMOUNT_MTAB=<path>
overrides the default location of the mtab file (ignored for
suid)
LIBMOUNT_DEBUG=all
enables libmount debug output
umount(2), losetup(8), mount(8)
A umount command appeared in Version 6 AT&T UNIX.
The umount command is part of the util-linux package and is available
from Linux Kernel Archive
⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩.
This page is part of the util-linux (a random collection of Linux
utilities) project. Information about the project can be found at
⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you have a
bug report for this manual page, send it to
util-linux@vger.kernel.org. This page was obtained from the
project's upstream Git repository
⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
2017-07-05. If you discover any rendering problems in this HTML ver‐
sion of the page, or you believe there is a better or more up-to-date
source for the page, or you have corrections or improvements to the
information in this COLOPHON (which is not part of the original man‐
ual page), send a mail to man-pages@man7.org
util-linux July 2014 UMOUNT(8)
Pages that refer to this page: eject(1), unshare(1), mount(2), umount(2), fstab(5), nfs(5), systemd.mount(5), blkdeactivate(8), mount(8), pivot_root(8), umount.nfs(8), xfs_repair(8)