Section: System Administration (8)
Updated: July 2014
umount - unmount filesystems
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also work, but is obsolete, mainly because it will fail in case this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
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.
- -a, --all
All of the filesystems described in
(or in deprecated
are unmounted, except the proc, devfs, devpts, sysfs, rpc_pipefs and nfsd
filesystems. This list of the filesystems may be replaced by --types
- -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
is a symlink
- -c, --no-canonicalize
Do not canonicalize paths. The paths canonicalization is based on
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
This option is silently ignored by
for non-root users.
For more details about this option see the
man page. Note that umount does not pass this option to the
- -d, --detach-loop
When the unmounted device was a loop device, also free this loop
device. This option is unnecessary for devices initialized by
in this case "autoclear" functionality is enabled by default.
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
that were unmounted earlier with the
- -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 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
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.
switches to the namespace when it reads
(or writes to
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
See mount_namespaces(7) for more information.
- -n, --no-mtab
Unmount without writing in
- -O, --test-opts option...
Unmount only the filesystems that have the specified option set in
More than one option may be specified in a comma-separated list.
Each option can be prefixed with
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
entries. The filesystem
must be specified by mountpoint path; a recursive unmount by device name (or UUID)
- -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
More than one type may be specified in a comma-separated list. The list
of filesystem types can be prefixed with
to indicate that no action should be taken for all of the mentioned types.
reads information about mounted filesystems from kernel (/proc/mounts) and
filesystem names may be different than filesystem names used in the
(e.g., "nfs4" vs. "nfs").
- -v, --verbose
- -V, --version
Display version information and exit.
- -h, --help
Display help text and exit.
Normally, only the superuser can umount filesystems.
option on a line, anybody can umount the corresponding filesystem. For more details see
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,
command will automatically detach loop device previously initialized by
command independently of
In this case the device is initialized with "autoclear" flag (see
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.
The syntax of external unmount helpers is:
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.
overrides the default location of the fstab file (ignored for suid)
overrides the default location of the mtab file (ignored for suid)
enables libmount debug output
table of mounted filesystems (deprecated and usually replaced by
table of known filesystems
table of mounted filesystems generated by kernel.
command appeared in Version 6 AT&T UNIX.
The umount command is part of the util-linux package and is available from
Linux Kernel Archive