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Linux 2.6 - man page for umount (linux section 8)

UMOUNT(8)			    Linux Programmer's Manual				UMOUNT(8)

       umount - unmount file systems

       umount [-hV]

       umount -a [-dflnrv] [-t vfstype] [-O options]
       umount [-dflnrv] {dir|device}...

       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       device  on  which  the file system lives may also work, but is obsolete, mainly because it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-

       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 sepa-
	      rated  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

       -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 ker-
	      nel 2.4.11 or later.)

	      Don't  canonicalize  paths. For more details about this option see the mount(8) man

       --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 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).

       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="  mtab	option.   The  -t
       option  is  used   for  filesystems with subtypes support (for example /sbin/mount.fuse -t

       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

       /etc/mtab table of mounted file systems

       umount(2), mount(8), losetup(8).

       A umount command appeared in Version 6 AT&T UNIX.

       The umount command is part of the util-linux package and is available from  ftp://ftp.ker-

Linux 2.0				   26 July 1997 				UMOUNT(8)

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