Provided by: mount_2.27.1-6ubuntu2_i386 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       lives may also work, but is obsolete, mainly because it  will  fail  in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 problem.


       -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

       -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

       --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

       -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 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.


              table of mounted filesystems

              table of known filesystems


              overrides  the  default  location of the fstab file (ignored for

              overrides the default location of the  mtab  file  (ignored  for

              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  ⟨