umount

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       lives may also work, but is obsolete, mainly because it  will  fail  in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 problem.

OPTIONS
       -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 speci-
              fied 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 avail-
              able). 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 filesys-
              tem.  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  pre-
              fixed 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
       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  los-
       etup(8)  output  for more details), otherwise it's necessary to use the
       option  --detach-loop or call losetup -d <device>. The  autoclear  fea-
       ture is supported since Linux 2.6.25.

EXTERNAL HELPERS
       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  mount-
       point  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.

FILES
       /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.

ENVIRONMENT
       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
       umount(2), losetup(8), mount(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 <https://www.kernel.org/pub/linux/utils/util-
       linux/>.

util-linux                         July 2014                         UMOUNT(8)
Man Pages Copyright Respective Owners. Site Copyright (C) 1994 - 2021 Hurricane Electric. All Rights Reserved.