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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | NON-SUPERUSER UMOUNTS | LOOP DEVICE | EXIT STATUS | EXTERNAL HELPERS | ENVIRONMENT | FILES | HISTORY | SEE ALSO | REPORTING BUGS | AVAILABILITY |
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UMOUNT(8) System Administration UMOUNT(8)
umount - unmount filesystems
umount -a [-dflnrv] [-t fstype] [-O option...]
umount [-dflnrv] {directory|device}
umount -h|-V
The umount command detaches the mentioned filesystem(s) from the
file hierarchy. A filesystem is specified by giving the directory
where it has been mounted. Giving the special device on which the
filesystem lives may also work, but is obsolete, mainly because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 filesystem 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, but it may introduce
other issues. See --lazy description below.
-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 mount 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.
This option is silently ignored by umount for non-root users.
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(2) and
stat(2) 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.
A system reboot would be expected in near future if you’re
going to use this option for network filesystem or local
filesystem with submounts. The recommended use-case for
umount -l is to prevent hangs on shutdown due to an
unreachable network share where a normal umount will hang due
to a downed server or a network partition. Remounts of the
share will not be possible.
-N, --namespace ns
Perform umount in the mount namespace specified by ns. ns is
either PID of process running in that namespace or special
file representing that namespace.
umount switches to the namespace when it reads /etc/fstab,
writes /etc/mtab (or writes to /run/mount) and calls
umount(2) system call, otherwise it runs in the original
namespace. It means that the target mount namespace does not
have to contain any libraries or other requirements necessary
to execute umount(2) command.
See mount_namespaces(7) for more information.
-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.
-q, --quiet
Suppress "not mounted" error messages.
-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.
Since version 2.37 it umounts also all over-mounted
filesystems (more filesystems on the same mountpoint).
-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.
-h, --help
Display help text and exit.
-V, --version
Print version and exit.
Normally, only the superuser can umount filesystems. However,
when fstab contains the user option on a line, anybody can umount
the corresponding filesystem. For more details see mount(8) man
page.
Since version 2.34 the umount command can be used to perform
umount operation also for fuse filesystems if kernel mount table
contains user’s ID. In this case fstab user= mount option is not
required.
Since version 2.35 umount command does not exit when user
permissions are inadequate by internal libmount security rules.
It drops suid permissions and continue as regular non-root user.
This can be used to support use-cases where root permissions are
not necessary (e.g., fuse filesystems, user namespaces, etc).
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.
umount has the following exit status values (the bits can be
ORed):
0
success
1
incorrect invocation or permissions
2
system error (out of memory, cannot fork, no more loop
devices)
4
internal mount bug
8
user interrupt
16
problems writing or locking /etc/mtab
32
mount failure
64
some umount succeeded
The command umount -a returns 0 (all succeeded), 32 (all
failed), or 64 (some failed, some succeeded).
126
failed to execute external /sbin/umount.<type> mount helper
(since util-linux v2.41)
The syntax of external unmount helpers is:
umount.suffix {directory|device} [-flnrv] [-N namespace]
[-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 other
userspace mount options are maintained by libmount.
The exit status value of the helper is returned as the exit
status of umount(8). The value 126 is used if the mount helper
program is found, but the execl() failed.
LIBMOUNT_FSTAB=<path>
overrides the default location of the fstab file (ignored for
suid)
LIBMOUNT_DEBUG=all
enables libmount debug output
/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.
A umount command appeared in Version 6 AT&T UNIX.
umount(2), losetup(8), mount_namespaces(7), mount(8)
For bug reports, use the issue tracker at
https://github.com/util-linux/util-linux/issues.
The umount command is part of the util-linux package which can be
downloaded 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
[email protected]. This page was obtained from the
project's upstream Git repository
⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
2024-06-14. (At that time, the date of the most recent commit
that was found in the repository was 2024-06-10.) If you discover
any rendering problems in this HTML version 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 manual page),
send a mail to [email protected]
util-linux 2.41.devel-537-e... 2024-06-13 UMOUNT(8)
Pages that refer to this page: eject(1), systemd-dissect(1), unshare(1), mount(2), umount(2), fstab(5), nfs(5), systemd.mount(5), cgroups(7), mount_namespaces(7), blkdeactivate(8), mount(8), pivot_root(8), umount(8), umount.nfs(8), xfs_repair(8)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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