Provided by: mount_2.27.1-6ubuntu3_amd64 bug


       umount - unmount file systems


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

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

       umount -h|-V


       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       device  on  which  the file system lives may also work, but is obsolete, mainly because it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


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

       -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.)

       -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.


       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).


       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

              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.


              table of mounted filesystems

              table of known filesystems


              overrides the default location of the fstab file (ignored for suid)

              overrides the default location of the mtab file (ignored for suid)

              enables libmount debug output


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


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


       The umount command is part of the util-linux package and is available  from  Linux  Kernel
       Archive ⟨⟩.