1UMOUNT(8) System Administration UMOUNT(8)
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6 umount - unmount file systems
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9 umount [-hV]
10 umount -a [-dflnrv] [-t vfstype] [-O options]
12 umount [-dflnrv] {dir|device}...
13
15 The umount command detaches the file system(s) mentioned from the file
16 hierarchy. A file system is specified by giving the directory where it
17 has been mounted. Giving the special device on which the file system
18 lives may also work, but is obsolete, mainly because it will fail in
19 case this device was mounted on more than one directory.
20 Note that a file system cannot be unmounted when it is 'busy' - for
22 example, when there are open files on it, or when some process has its
23 working directory there, or when a swap file on it is in use. The
24 offending process could even be umount itself - it opens libc, and libc
25 in its turn may open for example locale files. A lazy unmount avoids
26 this problem, but it may introduce another issues. See --lazy descrip‐
27 tion bellow.
28
30 -a, --all
31 All of the file systems described in /etc/mtab are unmounted.
32 (With umount version 2.7 and later: the proc filesystem is not
33 unmounted.)
34 -A, --all-targets
36 Unmount all mountpoints in the current namespace for the speci‐
37 fied filesystem. The filesystem could be specified by one of
38 the mountpoints or device name (or UUID, etc.). This option
39 could be used together with --recursive then all nested mounts
40 within the filesystem are recursively unmounted.
41 -c, --no-canonicalize
43 Do not canonicalize paths. For more details about this option
44 see the mount(8) man page.
45 -d, --detach-loop
47 When the unmounted device was a loop device, also free this loop
48 device. This option is unnecessary for devices initialized by
49 mount(8), in this case "autoclear" functionality is enabled by
50 default.
51 --fake Causes everything to be done except for the actual system call;
53 this 'fakes' unmounting the filesystem. It can be used to
54 remove entries from /etc/mtab that were unmounted earlier with
55 the -n option.
56 -f, --force
58 Force unmount (in case of an unreachable NFS system). (Requires
59 kernel 2.1.116 or later.)
60 -i, --internal-only
62 Do not call the /sbin/umount.<filesystem> helper even if it
63 exists. By default /sbin/umount.<filesystem> helper is called
64 if one exists.
65 -n, --no-mtab
67 Unmount without writing in /etc/mtab.
68 -l, --lazy
70 Lazy unmount. Detach the filesystem from the filesystem hierar‐
71 chy now, and cleanup all references to the filesystem as soon as
72 it is not busy anymore. (Requires kernel 2.4.11 or later.)
73 A system reboot would be expected in near future if you're going
75 to use this option for network filesystem or local filesystem
76 with submounts. The recommended use-case for umount -l is to
77 prevent hangs on shutdown due to an unreachable network share
78 where a normal umount will hang due to a downed server or a net‐
79 work partition. Remounts of the share will not be possible.
80 -O, --test-opts options,list
83 Indicate that the actions should only be taken on file systems
84 with the specified options in /etc/fstab. More than one option
85 type may be specified in a comma separated list. Each option
86 can be prefixed with no to specify options for which no action
87 should be taken.
88 -R, --recursive
90 Recursively unmount each directory specified. Recursion for each
91 directory will stop if any unmount operation in the chain fails
92 for any reason. The relationship between mountpoints is deter‐
93 mined by /proc/self/mountinfo entries. The filesystem must be
94 specified by mountpoint path, recursive unmount by device name
95 (or UUID) is unsupported.
96 -r, --read-only
98 In case unmounting fails, try to remount read-only.
99 -t, --types vfstype,ext2,ext3
101 Indicate that the actions should only be taken on file systems
102 of the specified type. More than one type may be specified in a
103 comma separated list. The list of file system types can be pre‐
104 fixed with no to specify the file system types on which no
105 action should be taken.
106 -v, --verbose
108 Verbose mode.
109 -h, --help
111 Print help message and exit.
112 -V, --version
114 Print version and exit.
115
117 The umount command will automatically detach loop device previously
118 initialized by mount(8) command independently of /etc/mtab.
119 In this case the device is initialized with "autoclear" flag (see los‐
121 etup(8) output for more details), otherwise it's necessary to use the
122 option --detach-loop or call losetup -d <device>. The autoclear fea‐
123 ture is supported since Linux 2.6.25.
124
126 The syntax of external umount helpers is:
127 /sbin/umount.<suffix> {dir|device} [-nlfvr] [-t type.subtype]
129 where the <suffix> is filesystem type or a value from "uhelper=" or
131 "helper=" mtab option. The -t option is used for filesystems with sub‐
132 types support (for example /sbin/mount.fuse -t fuse.sshfs).
133 The uhelper= (unprivileged umount helper) is possible to use when non-
135 root user wants to umount a mountpoint which is not defined in the
136 /etc/fstab file (e.g. devices mounted by udisk).
137 The helper= mount option redirects all umount requests to the
139 /sbin/umount.<helper> independently on UID.
140
142 /etc/mtab table of mounted file systems
143
145 LIBMOUNT_FSTAB=<path>
146 overrides the default location of the fstab file
147 LIBMOUNT_MTAB=<path>
149 overrides the default location of the mtab file
150 LIBMOUNT_DEBUG=0xffff
152 enables debug output
153
155 umount(2), mount(8), losetup(8)
156
158 A umount command appeared in Version 6 AT&T UNIX.
159
161 The umount command is part of the util-linux package and is available
162 from Linux Kernel Archive ⟨ftp://ftp.kernel.org/pub/linux/utils/util-
163 linux/⟩.
164util-linux August 2012 UMOUNT(8)