NAME

       umount - unmount file systems

SYNOPSIS

       umount [-hV]

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

DESCRIPTION

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       system  lives may also work, but is obsolete, mainly because it will fail in case this device was mounted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

       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 later.)

       -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.)

       --no-canonicalize
              Don't canonicalize paths. For more details about this option see the mount(8) man page.

       --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 LOOP DEVICE

       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).

NOTES

       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 udisk).

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

FILES

       /etc/mtab table of mounted file systems

SEE ALSO

       umount(2), mount(8), losetup(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
       ftp://ftp.kernel.org/pub/linux/utils/util-linux/.

util-linux                                         March 2010                                          UMOUNT(8)