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       device  on  which  the file system lives may also work, but is obsolete, mainly because it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

       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. helper  even  if  it  exists.  By  default
              /sbin/umount. 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. This allows an NFS-mounted filesystem to be  unmounted  if  the  NFS
              server  is  unreachable.  Note:  when  using  umount  -f  on an NFS filesystem, the
              filesystem must be mounted using either the soft,  or  intr  options  (see  nfs(5).
              This option will not force unmount a 'busy' filesystem (use -l instead).  (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. This option
              allows a 'busy' filesystem to be unmounted.  (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)