UMOUNT(8)						       System Administration							 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 Giving the special device on which the file system lives may also work, but is obsolete, mainly because it	will  fail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 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)