NAME

       umount - unmount filesystems

SYNOPSIS

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

       umount [-dflnrv] {directory|device}

       umount -h|-V

DESCRIPTION

       The umount command detaches the mentioned filesystem(s) from the file hierarchy. A filesystem is
       specified by giving the directory where it has been mounted. Giving the special device on which the
       filesystem lives may also work, but is obsolete, mainly because it will fail in case this device was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 filesystem 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, but it may introduce other issues. See --lazy
       description below.

OPTIONS

       -a, --all
           All of the filesystems described in /proc/self/mountinfo (or in deprecated /etc/mtab) are unmounted,
           except the proc, devfs, devpts, 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 mount namespace for the specified filesystem. The filesystem
           can be specified by one of the mountpoints or the device name (or UUID, etc.). When this option 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 available). The
           option has to be used with canonical path to the mount point.

           This option is silently ignored by umount for non-root users.

           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 filesystem. 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(2) and stat(2) system calls on
           unreachable NFS in umount.

       -i, --internal-only
           Do not call the /sbin/umount.filesystem helper even if it exists. 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 network partition. Remounts of the share will not be possible.

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

           umount 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 mount namespace does not have to contain any libraries or other requirements necessary to
           execute umount(2) command.

           See mount_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. Since version 2.37 it umounts also all over-mounted
           filesystems (more filesystems on the same mountpoint).

       -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 prefixed 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.

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

       -V, --version
           Print version and exit.

NON-SUPERUSER UMOUNTS

       Normally, only the superuser can umount filesystems. However, when fstab contains the user option on a
       line, anybody can umount the corresponding filesystem. For more details see mount(8) man page.

       Since version 2.34 the umount command can be used to perform umount operation also for fuse filesystems
       if kernel mount table contains user’s ID. In this case fstab user= mount option is not required.

       Since version 2.35 umount command does not exit when user permissions are inadequate by internal libmount
       security rules. It drops suid permissions and continue as regular non-root user. This can be used to
       support use-cases where root permissions are not necessary (e.g., fuse filesystems, user namespaces,
       etc).

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 losetup(8) output for more details),
       otherwise it’s necessary to use the option --detach-loop or call losetup -d device. The autoclear feature
       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 mountpoint 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 requests to the /sbin/umount.type helper
       independently of UID.

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

ENVIRONMENT

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

       LIBMOUNT_DEBUG=all
           enables libmount debug output

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.

HISTORY

       A umount command appeared in Version 6 AT&T UNIX.

SEE ALSO

       umount(2), losetup(8), mount_namespaces(7), mount(8)

REPORTING BUGS

       For bug reports, use the issue tracker at https://github.com/util-linux/util-linux/issues.

AVAILABILITY

       The umount command is part of the util-linux package which can be downloaded from Linux Kernel Archive
       <https://www.kernel.org/pub/linux/utils/util-linux/>.