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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       may  also  work, but is obsolete, mainly because it will fail in case this device was mounted on more than one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 specified 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.<filesys‐
              tem> 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 hierarchy 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
              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.

       -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 'los‐
       etup -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 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.

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/⟩.