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UMOUNT(8)                  Linux Programmer's Manual                 UMOUNT(8)



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.  Giv-
       ing  the  special device on which the file system lives may also work, but is obso-
       lete, 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 speci-
              fied  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  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.


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=" 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 used when non-root user
       wants to umount a mountpoint which is not  defined  in  the  /etc/fstab  file  (e.g
       devices mounted by HAL).


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-ng package and is available from
       ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.



Linux 2.0                        26 July 1997                        UMOUNT(8)

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