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. Giving the special device on which the file system lives may also work,  but  is
       obsolete, mainly because it will fail in case this device was mounted on more than one directory.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 prob-
       lem.

       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  filesys-
              tem 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]

       where the <suffix> is filesystem type or a value from "uhelper=" mtab option.

       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)