Provided by: mount_2.20.1-5.1ubuntu20.9_amd64 bug


       umount - unmount file systems


       umount [-hV]

       umount -a [-dflnrv] [-t vfstype] [-O options]
       umount [-dflnrv] {dir|device}...


       The  umount command detaches the file system(s) mentioned 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       device  on  which  the file system lives may also work, but is obsolete, mainly because it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

       Options for the umount command:

       -V     Print version and exit.

       -h     Print help message and exit.

       -v     Verbose mode.

       -n     Unmount without writing in /etc/mtab.

       -r     In case unmounting fails, try to remount read-only.

       -d     In case the unmounted device was a loop device, also free this loop device.

       -i     Don't call the /sbin/umount.<filesystem> helper  even  if  it  exists.  By  default
              /sbin/umount.<filesystem> helper is called if one exists.

       -a     All  of the file systems described in /etc/mtab are unmounted. (With umount version
              2.7 and later: the proc filesystem is not unmounted.)

       -t vfstype
              Indicate that the actions should only be taken on file  systems  of  the  specified
              type.   More than one type may be specified in a comma separated list.  The list of
              file system types can be prefixed with no to specify the file system types on which
              no action should be taken.

       -O options
              Indicate  that  the actions should only be taken on file systems with the specified
              options in /etc/fstab.  More than one option type  may  be  specified  in  a  comma
              separated  list.   Each option can be prefixed with no to specify options for which
              no action should be taken.

       -f     Force unmount (in case of an unreachable NFS system).  (Requires kernel 2.1.116  or

       -l     Lazy  unmount. Detach the filesystem from the filesystem hierarchy now, and cleanup
              all references to the filesystem as soon as it  is  not  busy  anymore.   (Requires
              kernel 2.4.11 or later.)

              Don't  canonicalize  paths. For more details about this option see the mount(8) man

       --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.


       The umount command will free the loop device (if any) associated with the mount,  in  case
       it finds the option `loop=...' in /etc/mtab, or when the -d option was given.  Any pending
       loop devices can be freed using `losetup -d', see losetup(8).


       The syntax of external umount helpers is:

       /sbin/umount.<suffix> {dir|device} [-nlfvr] [-t type.subtype]

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

       The uhelper= (unprivileged umount helper) is possible to use when non-root user  wants  to
       umount  a  mountpoint  which is not defined in the /etc/fstab file (e.g devices mounted by

       The helper= mount option  redirects  all  umount  requests  to  the  /sbin/umount.<helper>
       independently on UID.


       /etc/mtab table of mounted file systems


       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