umount(8) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | NON-SUPERUSER UMOUNTS | LOOP DEVICE | EXTERNAL HELPERS | ENVIRONMENT | FILES | HISTORY | SEE ALSO | REPORTING BUGS | AVAILABILITY

UMOUNT(8)                 System Administration                UMOUNT(8)

NAME         top

       umount - unmount filesystems

SYNOPSIS         top

       umount -a [-dflnrv] [-t fstype] [-O option...]

       umount [-dflnrv] {directory|device}

       umount -h|-V

DESCRIPTION         top

       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       filesystem lives may also work, but is obsolete, mainly because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.

OPTIONS         top

       -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 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.

           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.

       -V, --version
           Display version information and exit.

       -h, --help
           Display help text and exit.

NON-SUPERUSER UMOUNTS         top

       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).

LOOP DEVICE         top

       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.

EXTERNAL HELPERS         top

       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.

ENVIRONMENT         top

       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

FILES         top

       /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.

HISTORY         top

       A umount command appeared in Version 6 AT&T UNIX.

SEE ALSO         top

       umount(2), losetup(8), mount_namespaces(7), mount(8)

REPORTING BUGS         top

       For bug reports, use the issue tracker at
       https://github.com/karelzak/util-linux/issues.

AVAILABILITY         top

       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
       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
       2021-06-20. (At that time, the date of the most recent commit
       that was found in the repository was 2021-06-18.) 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 man-pages@man7.org

util-linux 2.37.85-637cc       2021-04-02                      UMOUNT(8)

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