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1 | .\" Copyright (c) 1996 Andries Brouwer | |
2 | .\" This page is somewhat derived from a page that was | |
3 | .\" (c) 1980, 1989, 1991 The Regents of the University of California | |
4 | .\" and had been heavily modified by Rik Faith and myself. | |
5 | .\" | |
6 | .\" This is free documentation; you can redistribute it and/or | |
7 | .\" modify it under the terms of the GNU General Public License as | |
8 | .\" published by the Free Software Foundation; either version 2 of | |
9 | .\" the License, or (at your option) any later version. | |
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11 | .\" The GNU General Public License's references to "object code" | |
12 | .\" and "executables" are to be interpreted as the output of any | |
13 | .\" document formatting or typesetting system, including | |
14 | .\" intermediate and printed output. | |
15 | .\" | |
16 | .\" This manual is distributed in the hope that it will be useful, | |
17 | .\" but WITHOUT ANY WARRANTY; without even the implied warranty of | |
18 | .\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
19 | .\" GNU General Public License for more details. | |
20 | .\" | |
21 | .\" You should have received a copy of the GNU General Public License along | |
22 | .\" with this program; if not, write to the Free Software Foundation, Inc., | |
23 | .\" 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. | |
24 | .\" | |
25 | .TH UMOUNT 8 "July 2014" "util-linux" "System Administration" | |
26 | .SH NAME | |
27 | umount \- unmount file systems | |
28 | .SH SYNOPSIS | |
29 | .B umount \-a | |
30 | .RB [ \-dflnrv ] | |
31 | .RB [ \-t | |
32 | .IR fstype ] | |
33 | .RB [ \-O | |
34 | .IR option ...] | |
35 | .sp | |
36 | .B umount | |
37 | .RB [ \-dflnrv ] | |
38 | .RI { directory | device }... | |
39 | .sp | |
40 | .B umount | |
41 | .BR \-h | \-V | |
42 | ||
43 | .SH DESCRIPTION | |
44 | The | |
45 | .B umount | |
46 | command detaches the mentioned file system(s) from the file hierarchy. A | |
47 | file system is specified by giving the directory where it has been | |
48 | mounted. Giving the special device on which the file system lives may | |
49 | also work, but is obsolete, mainly because it will fail in case this | |
50 | device was mounted on more than one directory. | |
51 | .PP | |
52 | Note that a file system cannot be unmounted when it is 'busy' - for | |
53 | example, when there are open files on it, or when some process has its | |
54 | working directory there, or when a swap file on it is in use. The | |
55 | offending process could even be | |
56 | .B umount | |
57 | itself - it opens libc, and libc in its turn may open for example locale | |
58 | files. A lazy unmount avoids this problem, but it may introduce another | |
59 | issues. See \fB\-\-lazy\fR description below. | |
60 | .SH OPTIONS | |
61 | .TP | |
62 | .BR \-a , " \-\-all" | |
63 | All of the filesystems described in | |
64 | .I /proc/self/mountinfo | |
65 | (or in deprecated /etc/mtab) | |
66 | are unmounted, except the proc, devfs, devpts, sysfs, rpc_pipefs and nfsd | |
67 | filesystems. This list of the filesystems may be replaced by \fB\-\-types\fR | |
68 | umount option. | |
69 | .TP | |
70 | .BR \-A , " \-\-all\-targets" | |
71 | Unmount all mountpoints in the current namespace for the specified filesystem. | |
72 | The filesystem can be specified by one of the mountpoints or the device name (or | |
73 | UUID, etc.). When this option is used together with \fB\-\-recursive\fR, then | |
74 | all nested mounts within the filesystem are recursively unmounted. | |
75 | This option is only supported on systems where /etc/mtab is a symlink | |
76 | to /proc/mounts. | |
77 | .TP | |
78 | .BR \-c , " \-\-no\-canonicalize" | |
79 | Do not canonicalize paths. The paths canonicalization is based on | |
80 | .BR stat (2) | |
81 | and | |
82 | .BR readlink (2) | |
83 | system calls. These system calls may hang in some cases (for example on NFS if | |
84 | server is not available). The option has to be used with canonical path to the | |
85 | mount point. | |
86 | ||
87 | For more details about this option see the | |
88 | .BR mount (8) | |
89 | man page. Note that \fBumount\fR does not pass this option to the | |
90 | .BI /sbin/umount. type | |
91 | helpers. | |
92 | .TP | |
93 | .BR \-d , " \-\-detach\-loop" | |
94 | When the unmounted device was a loop device, also free this loop | |
95 | device. This option is unnecessary for devices initialized by | |
96 | .BR mount (8), | |
97 | in this case "autoclear" functionality is enabled by default. | |
98 | .TP | |
99 | .B \-\-fake | |
100 | Causes everything to be done except for the actual system call or umount helper | |
101 | execution; this 'fakes' unmounting the filesystem. It can be used to remove | |
102 | entries from the deprecated | |
103 | .I /etc/mtab | |
104 | that were unmounted earlier with the | |
105 | .B \-n | |
106 | option. | |
107 | .TP | |
108 | .BR \-f , " \-\-force" | |
109 | Force an unmount (in case of an unreachable NFS system). | |
110 | ||
111 | Note that this option does not guarantee that umount command does not hang. | |
112 | It's strongly recommended to use absolute paths without symlinks to avoid | |
113 | unwanted readlink and stat system calls on unreachable NFS in umount. | |
114 | .TP | |
115 | .BR \-i , " \-\-internal\-only" | |
116 | Do not call the \fB/sbin/umount.\fIfilesystem\fR helper even if it exists. | |
117 | By default such a helper program is called if it exists. | |
118 | .TP | |
119 | .BR \-l , " \-\-lazy" | |
120 | Lazy unmount. Detach the filesystem from the file hierarchy now, | |
121 | and clean up all references to this filesystem as soon as it is not busy | |
122 | anymore. | |
123 | ||
124 | A system reboot would be expected in near future if you're going to use this | |
125 | option for network filesystem or local filesystem with submounts. The | |
126 | recommended use-case for \fBumount -l\fR is to prevent hangs on shutdown due to | |
127 | an unreachable network share where a normal umount will hang due to a downed | |
128 | server or a network partition. Remounts of the share will not be possible. | |
129 | ||
130 | .TP | |
131 | .BR \-N , " \-\-namespace " \fIns | |
132 | Perform umount in namespace specified by \fIns\fR. | |
133 | \fIns\fR is either PID of process running in that namespace | |
134 | or special file representing that namespace. | |
135 | .sp | |
136 | .BR umount (8) | |
137 | switches to the namespace when it reads /etc/fstab, writes /etc/mtab (or writes to /run/mount) and calls | |
138 | .BR umount (2) | |
139 | system call, otherwise it runs in the original namespace. It means that the target namespace does not have | |
140 | to contain any libraries or another requirements necessary to execute | |
141 | .BR umount (2) | |
142 | command. | |
143 | .sp | |
144 | See \fBnamespaces\fR(7) for more information. | |
145 | .TP | |
146 | .BR \-n , " \-\-no\-mtab" | |
147 | Unmount without writing in | |
148 | .IR /etc/mtab . | |
149 | .TP | |
150 | .BR \-O , " \-\-test\-opts " \fIoption\fR... | |
151 | Unmount only the filesystems that have the specified option set in | |
152 | .IR /etc/fstab . | |
153 | More than one option may be specified in a comma-separated list. | |
154 | Each option can be prefixed with | |
155 | .B no | |
156 | to indicate that no action should be taken for this option. | |
157 | .TP | |
158 | .BR \-q , " \-\-quiet" | |
159 | Suppress "not mounted" error messages. | |
160 | .TP | |
161 | .BR \-R , " \-\-recursive" | |
162 | Recursively unmount each specified directory. Recursion for each directory will | |
163 | stop if any unmount operation in the chain fails for any reason. The relationship | |
164 | between mountpoints is determined by /proc/self/mountinfo entries. The filesystem | |
165 | must be specified by mountpoint path; a recursive unmount by device name (or UUID) | |
166 | is unsupported. | |
167 | .TP | |
168 | .BR \-r , " \-\-read\-only" | |
169 | When an unmount fails, try to remount the filesystem read-only. | |
170 | .TP | |
171 | .BR \-t , " \-\-types " \fItype\fR... | |
172 | Indicate that the actions should only be taken on filesystems of the | |
173 | specified | |
174 | .IR type . | |
175 | More than one type may be specified in a comma-separated list. The list | |
176 | of filesystem types can be prefixed with | |
177 | .B no | |
178 | to indicate that no action should be taken for all of the mentioned types. | |
179 | Note that | |
180 | .B umount | |
181 | reads information about mounted filesystems from kernel (/proc/mounts) and | |
182 | filesystem names may be different than filesystem names used in the /etc/fstab | |
183 | (e.g. "nfs4" vs. "nfs"). | |
184 | .TP | |
185 | .BR \-v , " \-\-verbose" | |
186 | Verbose mode. | |
187 | .TP | |
188 | .BR \-V , " \-\-version" | |
189 | Display version information and exit. | |
190 | .TP | |
191 | .BR \-h , " \-\-help" | |
192 | Display help text and exit. | |
193 | .SH "LOOP DEVICE" | |
194 | The | |
195 | .B umount | |
196 | command will automatically detach loop device previously initialized by | |
197 | .BR mount (8) | |
198 | command independently of /etc/mtab. | |
199 | ||
200 | In this case the device is initialized with "autoclear" flag (see | |
201 | .BR losetup (8) | |
202 | output for more details), otherwise it's necessary to use the option \fB \-\-detach\-loop\fR | |
203 | or call \fBlosetup -d <device>\fR. The autoclear feature is supported since Linux 2.6.25. | |
204 | .SH EXTERNAL HELPERS | |
205 | The syntax of external unmount helpers is: | |
206 | .PP | |
207 | .RS | |
208 | .BI umount. suffix | |
209 | .RI { directory | device } | |
210 | .RB [ \-flnrv ] | |
211 | .RB [ \-N | |
212 | .IR namespace ] | |
213 | .RB [ \-t | |
214 | .IR type . subtype ] | |
215 | .RE | |
216 | .PP | |
217 | where \fIsuffix\fR is the filesystem type (or the value from a | |
218 | \fBuhelper=\fR or \fBhelper=\fR marker in the mtab file). | |
219 | The \fB\-t\fR option can be used for filesystems that | |
220 | have subtype support. For example: | |
221 | .PP | |
222 | .RS | |
223 | .B umount.fuse \-t fuse.sshfs | |
224 | .RE | |
225 | .PP | |
226 | A \fBuhelper=\fIsomething\fR marker (unprivileged helper) can appear in | |
227 | the \fI/etc/mtab\fR file when ordinary users need to be able to unmount | |
228 | a mountpoint that is not defined in \fI/etc/fstab\fR | |
229 | (for example for a device that was mounted by \fBudisks\fR(1)). | |
230 | .PP | |
231 | A \fBhelper=\fItype\fR marker in the mtab file will redirect | |
232 | all unmount requests | |
233 | to the \fB/sbin/umount.\fItype\fR helper independently of UID. | |
234 | .PP | |
235 | Note that \fI/etc/mtab\fR is currently deprecated and helper= and another | |
236 | userspace mount options are maintained by libmount. | |
237 | .SH FILES | |
238 | .TP | |
239 | .I /etc/mtab | |
240 | table of mounted filesystems (deprecated and usually replaced by | |
241 | symlink to /proc/mounts) | |
242 | .TP | |
243 | .I /etc/fstab | |
244 | table of known filesystems | |
245 | .TP | |
246 | .I /proc/self/mountinfo | |
247 | table of mounted filesystems generated by kernel. | |
248 | .SH ENVIRONMENT | |
249 | .IP LIBMOUNT_FSTAB=<path> | |
250 | overrides the default location of the fstab file (ignored for suid) | |
251 | .IP LIBMOUNT_MTAB=<path> | |
252 | overrides the default location of the mtab file (ignored for suid) | |
253 | .IP LIBMOUNT_DEBUG=all | |
254 | enables libmount debug output | |
255 | .SH "SEE ALSO" | |
256 | .BR umount (2), | |
257 | .BR losetup (8), | |
258 | .BR mount (8) | |
259 | .SH HISTORY | |
260 | A | |
261 | .B umount | |
262 | command appeared in Version 6 AT&T UNIX. | |
263 | .SH AVAILABILITY | |
264 | The umount command is part of the util-linux package and is available from | |
265 | .UR https://\:www.kernel.org\:/pub\:/linux\:/utils\:/util-linux/ | |
266 | Linux Kernel Archive | |
267 | .UE . |