1UMOUNT(8)                    System Administration                   UMOUNT(8)
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NAME

6       umount - unmount filesystems
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SYNOPSIS

9       umount -a [-dflnrv] [-t fstype] [-O option...]
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11       umount [-dflnrv] {directory|device}
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13       umount -h|-V
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DESCRIPTION

16       The umount command detaches the mentioned filesystem(s) from the file
17       hierarchy. A filesystem is specified by giving the directory where it
18       has been mounted. Giving the special device on which the filesystem
19       lives may also work, but is obsolete, mainly because it will fail in
20       case this device was mounted on more than one directory.
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22       Note that a filesystem cannot be unmounted when it is 'busy' - for
23       example, when there are open files on it, or when some process has its
24       working directory there, or when a swap file on it is in use. The
25       offending process could even be umount itself - it opens libc, and libc
26       in its turn may open for example locale files. A lazy unmount avoids
27       this problem, but it may introduce other issues. See --lazy description
28       below.
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OPTIONS

31       -a, --all
32           All of the filesystems described in /proc/self/mountinfo (or in
33           deprecated /etc/mtab) are unmounted, except the proc, devfs,
34           devpts, sysfs, rpc_pipefs and nfsd filesystems. This list of the
35           filesystems may be replaced by --types umount option.
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37       -A, --all-targets
38           Unmount all mountpoints in the current mount namespace for the
39           specified filesystem. The filesystem can be specified by one of the
40           mountpoints or the device name (or UUID, etc.). When this option is
41           used together with --recursive, then all nested mounts within the
42           filesystem are recursively unmounted. This option is only supported
43           on systems where /etc/mtab is a symlink to /proc/mounts.
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45       -c, --no-canonicalize
46           Do not canonicalize paths. The paths canonicalization is based on
47           stat(2) and readlink(2) system calls. These system calls may hang
48           in some cases (for example on NFS if server is not available). The
49           option has to be used with canonical path to the mount point.
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51           This option is silently ignored by umount for non-root users.
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53           For more details about this option see the mount(8) man page. Note
54           that umount does not pass this option to the /sbin/umount.type
55           helpers.
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57       -d, --detach-loop
58           When the unmounted device was a loop device, also free this loop
59           device. This option is unnecessary for devices initialized by
60           mount(8), in this case "autoclear" functionality is enabled by
61           default.
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63       --fake
64           Causes everything to be done except for the actual system call or
65           umount helper execution; this 'fakes' unmounting the filesystem. It
66           can be used to remove entries from the deprecated /etc/mtab that
67           were unmounted earlier with the -n option.
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69       -f, --force
70           Force an unmount (in case of an unreachable NFS system).
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72           Note that this option does not guarantee that umount command does
73           not hang. It’s strongly recommended to use absolute paths without
74           symlinks to avoid unwanted readlink(2) and stat(2) system calls on
75           unreachable NFS in umount.
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77       -i, --internal-only
78           Do not call the /sbin/umount.filesystem helper even if it exists.
79           By default such a helper program is called if it exists.
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81       -l, --lazy
82           Lazy unmount. Detach the filesystem from the file hierarchy now,
83           and clean up all references to this filesystem as soon as it is not
84           busy anymore.
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86           A system reboot would be expected in near future if you’re going to
87           use this option for network filesystem or local filesystem with
88           submounts. The recommended use-case for umount -l is to prevent
89           hangs on shutdown due to an unreachable network share where a
90           normal umount will hang due to a downed server or a network
91           partition. Remounts of the share will not be possible.
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93       -N, --namespace ns
94           Perform umount in the mount namespace specified by ns. ns is either
95           PID of process running in that namespace or special file
96           representing that namespace.
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98           umount switches to the namespace when it reads /etc/fstab, writes
99           /etc/mtab (or writes to /run/mount) and calls umount(2) system
100           call, otherwise it runs in the original namespace. It means that
101           the target mount namespace does not have to contain any libraries
102           or other requirements necessary to execute umount(2) command.
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104           See mount_namespaces(7) for more information.
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106       -n, --no-mtab
107           Unmount without writing in /etc/mtab.
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109       -O, --test-opts option...
110           Unmount only the filesystems that have the specified option set in
111           /etc/fstab. More than one option may be specified in a
112           comma-separated list. Each option can be prefixed with no to
113           indicate that no action should be taken for this option.
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115       -q, --quiet
116           Suppress "not mounted" error messages.
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118       -R, --recursive
119           Recursively unmount each specified directory. Recursion for each
120           directory will stop if any unmount operation in the chain fails for
121           any reason. The relationship between mountpoints is determined by
122           /proc/self/mountinfo entries. The filesystem must be specified by
123           mountpoint path; a recursive unmount by device name (or UUID) is
124           unsupported. Since version 2.37 it umounts also all over-mounted
125           filesystems (more filesystems on the same mountpoint).
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127       -r, --read-only
128           When an unmount fails, try to remount the filesystem read-only.
129
130       -t, --types type...
131           Indicate that the actions should only be taken on filesystems of
132           the specified type. More than one type may be specified in a
133           comma-separated list. The list of filesystem types can be prefixed
134           with no to indicate that no action should be taken for all of the
135           mentioned types. Note that umount reads information about mounted
136           filesystems from kernel (/proc/mounts) and filesystem names may be
137           different than filesystem names used in the /etc/fstab (e.g.,
138           "nfs4" vs. "nfs").
139
140       -v, --verbose
141           Verbose mode.
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143       -h, --help
144           Display help text and exit.
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146       -V, --version
147           Print version and exit.
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NON-SUPERUSER UMOUNTS

150       Normally, only the superuser can umount filesystems. However, when
151       fstab contains the user option on a line, anybody can umount the
152       corresponding filesystem. For more details see mount(8) man page.
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154       Since version 2.34 the umount command can be used to perform umount
155       operation also for fuse filesystems if kernel mount table contains
156       user’s ID. In this case fstab user= mount option is not required.
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158       Since version 2.35 umount command does not exit when user permissions
159       are inadequate by internal libmount security rules. It drops suid
160       permissions and continue as regular non-root user. This can be used to
161       support use-cases where root permissions are not necessary (e.g., fuse
162       filesystems, user namespaces, etc).
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LOOP DEVICE

165       The umount command will automatically detach loop device previously
166       initialized by mount(8) command independently of /etc/mtab.
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168       In this case the device is initialized with "autoclear" flag (see
169       losetup(8) output for more details), otherwise it’s necessary to use
170       the option --detach-loop or call losetup -d device. The autoclear
171       feature is supported since Linux 2.6.25.
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EXTERNAL HELPERS

174       The syntax of external unmount helpers is:
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176          umount.suffix {directory|device} [-flnrv] [-N namespace] [-t
177          type.subtype]
178
179       where suffix is the filesystem type (or the value from a uhelper= or
180       helper= marker in the mtab file). The -t option can be used for
181       filesystems that have subtype support. For example:
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183          umount.fuse -t fuse.sshfs
184
185       A uhelper=something marker (unprivileged helper) can appear in the
186       /etc/mtab file when ordinary users need to be able to unmount a
187       mountpoint that is not defined in /etc/fstab (for example for a device
188       that was mounted by udisks(1)).
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190       A helper=type marker in the mtab file will redirect all unmount
191       requests to the /sbin/umount.type helper independently of UID.
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193       Note that /etc/mtab is currently deprecated and helper= and other
194       userspace mount options are maintained by libmount.
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ENVIRONMENT

197       LIBMOUNT_FSTAB=<path>
198           overrides the default location of the fstab file (ignored for suid)
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200       LIBMOUNT_MTAB=<path>
201           overrides the default location of the mtab file (ignored for suid)
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203       LIBMOUNT_DEBUG=all
204           enables libmount debug output
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FILES

207       /etc/mtab
208           table of mounted filesystems (deprecated and usually replaced by
209           symlink to /proc/mounts)
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211       /etc/fstab
212           table of known filesystems
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214       /proc/self/mountinfo
215           table of mounted filesystems generated by kernel.
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HISTORY

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

221       umount(2), losetup(8), mount_namespaces(7), mount(8)
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REPORTING BUGS

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

228       The umount command is part of the util-linux package which can be
229       downloaded from Linux Kernel Archive
230       <https://www.kernel.org/pub/linux/utils/util-linux/>.
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234util-linux 2.38                   2022-02-17                         UMOUNT(8)
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