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       lives may also work, but is obsolete, mainly because it  will  fail  in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

       -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 pre-
              fixed 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
              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 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=" 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.

       /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

util-linux                        March 2010                         UMOUNT(8)
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