UMOUNT linux command manual

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       tem lives may also work, but is obsolete, mainly because it will  fail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.

       -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 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).


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)