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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.  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       lives may also work, but is obsolete, mainly because it	will  fail  in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 pre-
	      fixed 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  hierar-
	      chy now, and cleanup all references to the filesystem as soon as
	      it is not busy anymore.  (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).


NOTES
       The syntax of external umount helpers is:

       /sbin/umount.<suffix> [-nlfvr] dir | device

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

       The uhelper (unprivileged umount request helper) is possible 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.



Linux 2.0			 26 July 1997			     UMOUNT(8)
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