1UMOUNT(8) System Administration UMOUNT(8)
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6 umount - unmount file systems
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9 umount -a [-dflnrv] [-t fstype] [-O option...]
10 umount [-dflnrv] {directory|device}...
12 umount -h|-V
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17 The umount command detaches the mentioned file system(s) from the file
18 hierarchy. A file system is specified by giving the directory where it
19 has been mounted. Giving the special device on which the file system
20 lives may also work, but is obsolete, mainly because it will fail in
21 case this device was mounted on more than one directory.
22 Note that a file system cannot be unmounted when it is 'busy' - for
24 example, when there are open files on it, or when some process has its
25 working directory there, or when a swap file on it is in use. The
26 offending process could even be umount itself - it opens libc, and libc
27 in its turn may open for example locale files. A lazy unmount avoids
28 this problem, but it may introduce another issues. See --lazy descrip‐
29 tion bellow.
30
32 -a, --all
33 All of the filesystems described in /proc/self/mountinfo (or in
34 deprecated /etc/mtab) are unmounted, except the proc, devfs,
35 devpts, sysfs, rpc_pipefs and nfsd filesystems. This list of the
36 filesystems may be replaced by --types umount option.
37 -A, --all-targets
39 Unmount all mountpoints in the current namespace for the speci‐
40 fied filesystem. The filesystem can be specified by one of the
41 mountpoints or the device name (or UUID, etc.). When this
42 option is used together with --recursive, then all nested mounts
43 within the filesystem are recursively unmounted. This option is
44 only supported on systems where /etc/mtab is a symlink to
45 /proc/mounts.
46 -c, --no-canonicalize
48 Do not canonicalize paths. The paths canonicalization is based
49 on stat(2) and readlink(2) system calls. These system calls may
50 hang in some cases (for example on NFS if server is not avail‐
51 able). The option has to be used with canonical path to the
52 mount point.
53 For more details about this option see the mount(8) man page.
55 Note that umount does not pass this option to the
56 /sbin/umount.type helpers.
57 -d, --detach-loop
59 When the unmounted device was a loop device, also free this loop
60 device. This option is unnecessary for devices initialized by
61 mount(8), in this case "autoclear" functionality is enabled by
62 default.
63 --fake Causes everything to be done except for the actual system call
65 or umount helper execution; this 'fakes' unmounting the filesys‐
66 tem. It can be used to remove entries from the deprecated
67 /etc/mtab that were unmounted earlier with the -n option.
68 -f, --force
70 Force an unmount (in case of an unreachable NFS system).
71 Note that this option does not guarantee that umount command
73 does not hang. It's strongly recommended to use absolute paths
74 without symlinks to avoid unwanted readlink and stat system
75 calls on unreachable NFS in umount.
76 -i, --internal-only
78 Do not call the /sbin/umount.filesystem helper even if it
79 exists. By default such a helper program is called if it
80 exists.
81 -l, --lazy
83 Lazy unmount. Detach the filesystem from the file hierarchy
84 now, and clean up all references to this filesystem as soon as
85 it is not busy anymore.
86 A system reboot would be expected in near future if you're going
88 to use this option for network filesystem or local filesystem
89 with submounts. The recommended use-case for umount -l is to
90 prevent hangs on shutdown due to an unreachable network share
91 where a normal umount will hang due to a downed server or a net‐
92 work partition. Remounts of the share will not be possible.
93 -n, --no-mtab
96 Unmount without writing in /etc/mtab.
97 -O, --test-opts option...
99 Unmount only the filesystems that have the specified option set
100 in /etc/fstab. More than one option may be specified in a
101 comma-separated list. Each option can be prefixed with no to
102 indicate that no action should be taken for this option.
103 -R, --recursive
105 Recursively unmount each specified directory. Recursion for
106 each directory will stop if any unmount operation in the chain
107 fails for any reason. The relationship between mountpoints is
108 determined by /proc/self/mountinfo entries. The filesystem must
109 be specified by mountpoint path; a recursive unmount by device
110 name (or UUID) is unsupported.
111 -r, --read-only
113 When an unmount fails, try to remount the filesystem read-only.
114 -t, --types type...
116 Indicate that the actions should only be taken on filesystems of
117 the specified type. More than one type may be specified in a
118 comma-separated list. The list of filesystem types can be pre‐
119 fixed with no to indicate that no action should be taken for all
120 of the mentioned types. Note that umount reads information
121 about mounted filesystems from kernel (/proc/mounts) and
122 filesystem names may be different than filesystem names used in
123 the /etc/fstab (e.g. "nfs4" vs. "nfs").
124 -v, --verbose
126 Verbose mode.
127 -V, --version
129 Display version information and exit.
130 -h, --help
132 Display help text and exit.
133
135 The umount command will automatically detach loop device previously
136 initialized by mount(8) command independently of /etc/mtab.
137 In this case the device is initialized with "autoclear" flag (see los‐
139 etup(8) output for more details), otherwise it's necessary to use the
140 option --detach-loop or call losetup -d <device>. The autoclear fea‐
141 ture is supported since Linux 2.6.25.
142
144 The syntax of external unmount helpers is:
145 umount.suffix {directory|device} [-flnrv] [-t type.subtype]
147 where suffix is the filesystem type (or the value from a uhelper= or
149 helper= marker in the mtab file). The -t option can be used for
150 filesystems that have subtype support. For example:
151 umount.fuse -t fuse.sshfs
153 A uhelper=something marker (unprivileged helper) can appear in the
155 /etc/mtab file when ordinary users need to be able to unmount a mount‐
156 point that is not defined in /etc/fstab (for example for a device that
157 was mounted by udisks(1)).
158 A helper=type marker in the mtab file will redirect all unmount
160 requests to the /sbin/umount.type helper independently of UID.
161 Note that /etc/mtab is currently deprecated and helper= and another
163 userspace mount options are maintained by libmount.
164
166 /etc/mtab
167 table of mounted filesystems (deprecated and usually replaced by
168 symlink to /proc/mounts)
169 /etc/fstab
171 table of known filesystems
172 /proc/self/mountinfo
174 table of mounted filesystems generated by kernel.
175
177 LIBMOUNT_FSTAB=<path>
178 overrides the default location of the fstab file (ignored for
179 suid)
180 LIBMOUNT_MTAB=<path>
182 overrides the default location of the mtab file (ignored for
183 suid)
184 LIBMOUNT_DEBUG=all
186 enables libmount debug output
187
189 umount(2), losetup(8), mount(8)
190
192 A umount command appeared in Version 6 AT&T UNIX.
193
195 The umount command is part of the util-linux package and is available
196 from Linux Kernel Archive ⟨https://www.kernel.org/pub/linux/utils/util-
197 linux/⟩.
198util-linux July 2014 UMOUNT(8)