UMOUNT(8)                             System Administration                             UMOUNT(8)



NAME
       umount - unmount file systems

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

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

       umount -h|-V


DESCRIPTION
       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       device  on  which  the file system lives may also work, but is obsolete, mainly because it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 prob‐
       lem.

OPTIONS
       -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;  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.)

       -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.

       -v, --verbose
              Verbose mode.

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

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

LOOP DEVICE
       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
       The syntax of external unmount helpers is:

       /sbin/umount.suffix {directory|device} [-flnrv] [-t type.subtype]

       where suffix is the filesystem type or a value from a "uhelper=" or "helper=" mtab option.
       The  -t  option  can  be  used  for  filesystems  with  subtypes  support   (for   example
       /sbin/mount.fuse -t fuse.sshfs).

       The  uhelper=  (unprivileged  unmount helper) mount option can be used when non-root users
       need to be able to unmount a mountpoint which is not defined in /etc/fstab  (e.g.  devices
       mounted by udisk).

       The  helper=  mount  option redirects all unmount requests to the /sbin/umount.type helper
       independently of UID.

FILES
       /etc/mtab
              table of mounted filesystems

       /etc/fstab
              checked when option -O is given

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 ALSO
       umount(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                                  July 2014                                   UMOUNT(8)