NAME | SYNOPSIS | DESCRIPTION | OPTIONS | LOOP DEVICE | EXTERNAL HELPERS | FILES | ENVIRONMENT | SEE ALSO | HISTORY | AVAILABILITY | COLOPHON

UMOUNT(8)                   System Administration                  UMOUNT(8)

NAME         top

       umount - unmount file systems

SYNOPSIS         top

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

       umount [-dflnrv] {directory|device}...

       umount -h|-V

DESCRIPTION         top

       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       file system lives may also work, but is obsolete, mainly because it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.

OPTIONS         top

       -a, --all
              All of the filesystems described in /etc/mtab are unmounted,
              except the proc filesystem.

       -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.  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.

       --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 /etc/mtab
              that were unmounted earlier with the -n option.

       -f, --force
              Force an unmount (in case of an unreachable NFS system).
              (Requires kernel 2.1.116 or later.)

              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
              syscalls 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.  (Requires kernel 2.4.11 or later.)

       -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.

LOOP DEVICE         top

       The umount command will free the loop device associated with a mount
       when it finds the option loop=... in /etc/mtab, or when the -d option
       was given.  Any still associated loop devices can be freed by using
       losetup -d; see losetup(8).

EXTERNAL HELPERS         top

       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.

FILES         top

       /etc/mtab
              table of mounted filesystems

       /etc/fstab
              table of known filesystems

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

SEE ALSO         top

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

HISTORY         top

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

AVAILABILITY         top

       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/⟩.

COLOPHON         top

       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
       2016-08-07.  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)