umount - unmount filesystems
umount -a [-dflnrv] [-t fstype] [-O
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work, but is obsolete, mainly because it will fail in case this device was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.
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.
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.
Do not canonicalize paths. The paths canonicalization is
based on stat(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
For more details about this option see the mount(8) man
page. Note that umount does not pass this option to the
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
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.
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
Do not call the /sbin/umount.filesystem
helper even if it exists. By default such a helper program is called if it
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
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)
See mount_namespaces(7) for more information.
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.
Suppress "not mounted" error messages.
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).
When an unmount fails, try to remount the filesystem
-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.
Display version information and exit.
Display help text and exit.
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
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).
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
The syntax of external unmount helpers is:
[-flnrv] [-N namespace] [-t
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
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
overrides the default location of the fstab file (ignored
overrides the default location of the mtab file (ignored
enables libmount debug output
table of mounted filesystems (deprecated and usually
replaced by symlink to /proc/mounts)
table of known filesystems
table of mounted filesystems generated by kernel.
A umount command appeared in Version 6 AT&T UNIX.