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       system lives may also work, but is obsolete, mainly because it will fail in case this device was  mounted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 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.

              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.

       -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

       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

       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.

       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.

util-linux                                          July 2014                                          UMOUNT(8)