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 sys-
       tem lives may also work, but is obsolete, mainly because it will	 fail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.  helper  even if it
	      exists. By default /sbin/umount. 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.  This  allows  an	 NFS-mounted filesystem to be
	      unmounted if the NFS server is unreachable.  Note:  when	using
	      umount  -f on an NFS filesystem, the filesystem must be mounted
	      using either the soft,  or  intr	options	 (see  nfs(5).	 This
	      option  will  not	 force	unmount	 a  'busy' filesystem (use -l
	      instead).	 (Requires kernel 2.1.116 or later.)

       -l     Lazy unmount. Detach the filesystem from the filesystem hierar-
	      chy  now,	 and cleanup all references to the filesystem as soon
	      as it is not busy anymore. This option allows a 'busy' filesys-
	      tem to be unmounted.  (Requires kernel 2.4.11 or later.)


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).


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.



Linux 2.0			 26 July 1997			    UMOUNT(8)

UNIX/Linux commands referenced on this page:

1. file
2. dir
3. which
4. more
5. locale
6. as
7. free
8. mount
9. losetup