umount

UMOUNT(8)                    System Administration                   UMOUNT(8)

NAME
       umount - unmount file systems

SYNOPSIS
       umount -a [-dflnrv] [-t fstype] [-O option...]

       umount [-dflnrv] {directory|device}...

       umount -h|-V

DESCRIPTION
       The  umount command detaches the mentioned file system(s) 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       lives may also work, but is obsolete, mainly because it  will  fail  in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 ex-
       ample, 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 of-
       fending 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, but it may introduce another issues. See --lazy  descrip-
       tion below.

OPTIONS
       -a, --all
              All  of the filesystems described in /proc/self/mountinfo (or in
              deprecated /etc/mtab) are unmounted, except the proc, devfs, de-
              vpts,  sysfs,  rpc_pipefs and nfsd filesystems. This list of the
              filesystems may be replaced by --types umount option.

       -A, --all-targets
              Unmount all mountpoints in the current namespace for the  speci-
              fied  filesystem.  The filesystem can be specified by one of the
              mountpoints or the device name (or UUID, etc.).  When  this  op-
              tion  is  used together with --recursive, then all nested mounts
              within the filesystem are recursively unmounted.  This option is
              only  supported  on  systems  where  /etc/mtab  is  a symlink to
              /proc/mounts.

       -c, --no-canonicalize
              Do not canonicalize paths.  The paths canonicalization is  based
              on  stat(2) and readlink(2) system calls. These system calls may
              hang in some cases (for example on NFS if server is  not  avail-
              able).  The  option  has  to  be used with canonical path to the
              mount point.

              For more details about this option see the  mount(8)  man  page.
              Note   that   umount   does   not   pass   this  option  to  the
              /sbin/umount.type helpers.

       -d, --detach-loop
              When the unmounted device was a loop device, also free this loop
              device.  This  option  is unnecessary for devices initialized by
              mount(8), in this case "autoclear" functionality is  enabled  by
              default.

       --fake Causes  everything  to be done except for the actual system call
              or umount helper execution; this 'fakes' unmounting the filesys-
              tem.   It  can  be  used  to  remove entries from the deprecated
              /etc/mtab that were unmounted earlier with the -n option.

       -f, --force
              Force an unmount (in case of an unreachable NFS system).

              Note that this option does not  guarantee  that  umount  command
              does  not hang.  It's strongly recommended to use absolute paths
              without symlinks to avoid  unwanted  readlink  and  stat  system
              calls on unreachable NFS in umount.

       -i, --internal-only
              Do  not  call  the /sbin/umount.filesystem helper even if it ex-
              ists.  By default such a helper program is called if it exists.

       -l, --lazy
              Lazy unmount.  Detach the filesystem  from  the  file  hierarchy
              now,  and  clean up all references to this filesystem as soon as
              it is not busy anymore.

              A system reboot would be expected in near future if you're going
              to  use  this  option for network filesystem or local filesystem
              with submounts.  The recommended use-case for umount  -l  is  to
              prevent  hangs  on  shutdown due to an unreachable network share
              where a normal umount will hang due to a downed server or a net-
              work partition. Remounts of the share will not be possible.

       -N, --namespace ns
              Perform  umount  in namespace specified by ns.  ns is either PID
              of process running in that namespace or special file  represent-
              ing that namespace.

              umount(8)  switches  to  the namespace when it reads /etc/fstab,
              writes /etc/mtab (or writes to /run/mount) and  calls  umount(2)
              system  call,  otherwise  it  runs in the original namespace. It
              means that the target namespace does not have to contain any li-
              braries  or  another requirements necessary to execute umount(2)
              command.

              See namespaces(7) for more information.

       -n, --no-mtab
              Unmount without writing in /etc/mtab.

       -O, --test-opts option...
              Unmount only the filesystems that have the specified option  set
              in  /etc/fstab.   More  than  one  option  may be specified in a
              comma-separated list.  Each option can be prefixed  with  no  to
              indicate that no action should be taken for this option.

       -q, --quiet
              Suppress "not mounted" error messages.

       -R, --recursive
              Recursively  unmount  each  specified  directory.  Recursion for
              each directory will stop if any unmount operation in  the  chain
              fails  for  any reason.  The relationship between mountpoints is
              determined by /proc/self/mountinfo entries.  The filesystem must
              be  specified  by mountpoint path; a recursive unmount by device
              name (or UUID) is unsupported.

       -r, --read-only
              When an unmount fails, try to remount the filesystem read-only.

       -t, --types type...
              Indicate that the actions should only be taken on filesystems of
              the  specified  type.   More than one type may be specified in a
              comma-separated list.  The list of filesystem types can be  pre-
              fixed with no to indicate that no action should be taken for all
              of the mentioned types.   Note  that  umount  reads  information
              about   mounted   filesystems  from  kernel  (/proc/mounts)  and
              filesystem names may be different than filesystem names used  in
              the /etc/fstab (e.g. "nfs4" vs. "nfs").

       -v, --verbose
              Verbose mode.

       -V, --version
              Display version information and exit.

       -h, --help
              Display help text and exit.

LOOP DEVICE
       The  umount  command  will  automatically detach loop device previously
       initialized by mount(8) command independently of /etc/mtab.

       In this case the device is initialized with "autoclear" flag (see  los-
       etup(8)  output  for more details), otherwise it's necessary to use the
       option  --detach-loop or call losetup -d <device>. The  autoclear  fea-
       ture is supported since Linux 2.6.25.

EXTERNAL HELPERS
       The syntax of external unmount helpers is:

              umount.suffix  {directory|device}  [-flnrv]  [-N  namespace] [-t
              type.subtype]

       where suffix is the filesystem type (or the value from  a  uhelper=  or
       helper=  marker  in  the  mtab  file).   The  -t option can be used for
       filesystems that have subtype support.  For example:

              umount.fuse -t fuse.sshfs

       A uhelper=something marker (unprivileged  helper)  can  appear  in  the
       /etc/mtab  file when ordinary users need to be able to unmount a mount-
       point that is not defined in /etc/fstab (for example for a device  that
       was mounted by udisks(1)).

       A  helper=type  marker  in  the mtab file will redirect all unmount re-
       quests to the /sbin/umount.type helper independently of UID.

       Note that /etc/mtab is currently deprecated  and  helper=  and  another
       userspace mount options are maintained by libmount.

FILES
       /etc/mtab
              table of mounted filesystems (deprecated and usually replaced by
              symlink to /proc/mounts)

       /etc/fstab
              table of known filesystems

       /proc/self/mountinfo
              table of mounted filesystems generated by kernel.

ENVIRONMENT
       LIBMOUNT_FSTAB=<path>
              overrides the default location of the fstab  file  (ignored  for
              suid)

       LIBMOUNT_MTAB=<path>
              overrides  the  default  location  of the mtab file (ignored for
              suid)

       LIBMOUNT_DEBUG=all
              enables libmount debug output

SEE ALSO
       umount(2), losetup(8), mount(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 <https://www.kernel.org/pub/linux/utils/util-
       linux/>.

util-linux                         July 2014                         UMOUNT(8)