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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       lives may also work, but is obsolete, mainly because it	will  fail  in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
       -a, --all
	      All of the file systems described in  /etc/mtab  are  unmounted.
	      (With  umount  version 2.7 and later: the proc filesystem is not
	      unmounted.)

       -A, --all-targets
	      Unmount all mountpoints in the current namespace for the	speci-
	      fied  filesystem.	  The  filesystem could be specified by one of
	      the mountpoints or device name  (or  UUID,  etc.).  This	option
	      could  be	 used together with --recursive then all nested mounts
	      within the filesystem are recursively unmounted.

       -c, --no-canonicalize
	      Do not canonicalize paths.  For more details about  this	option
	      see the mount(8) man page.

       -d, --detach-loop
	      In  case	the unmounted device was a loop device, also free this
	      loop device.

       --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.

       -f, --force
	      Force unmount (in case of an unreachable NFS system).  (Requires
	      kernel 2.1.116 or later.)

       -i, --internal-only
	      Do not call the  /sbin/umount.<filesystem>  helper  even	if  it
	      exists.	By  default /sbin/umount.<filesystem> helper is called
	      if one exists.

       -n, --no-mtab
	      Unmount without writing in /etc/mtab.

       -l, --lazy
	      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.)

       -O, --test-opts options,list
	      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.

       -R, --recursive
	      Recursively unmount each directory specified. Recursion for each
	      directory	 will stop if any unmount operation in the chain fails
	      for any reason. The relationship between mountpoints  is	deter-
	      mined  by	 /proc/self/mountinfo  entries. The filesystem must be
	      specified by mountpoint path, recursive unmount by  device  name
	      (or UUID) is unsupported.

       -r, --read-only
	      In case unmounting fails, try to remount read-only.

       -t, --types vfstype,ext2,ext3
	      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.

       -v, --verbose
	      Verbose mode.

       -h, --help
	      Print help message and exit.

       -V, --version
	      Print version and exit.

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 sub-
       types 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

ENVIRONMENT
       LIBMOUNT_FSTAB=<path>
	      overrides the default location of the fstab file

       LIBMOUNT_MTAB=<path>
	      overrides the default location of the mtab file

       LIBMOUNT_DEBUG=0xffff
	      enables debug output

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 Linux Kernel  Archive  <ftp://ftp.kernel.org/pub/linux/utils/util-
       linux/>.



util-linux			  August 2012			     UMOUNT(8)