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1 | .\" Copyright (C) 1993 Rickard E. Faith <faith@cs.unc.edu> |
2 | .\" and Copyright (C) 1994 Andries E. Brouwer <aeb@cwi.nl> | |
3 | .\" and Copyright (C) 2002, 2005 Michael Kerrisk <mtk.manpages@gmail.com> | |
4 | .\" | |
93015253 | 5 | .\" %%%LICENSE_START(VERBATIM) |
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6 | .\" Permission is granted to make and distribute verbatim copies of this |
7 | .\" manual provided the copyright notice and this permission notice are | |
8 | .\" preserved on all copies. | |
9 | .\" | |
10 | .\" Permission is granted to copy and distribute modified versions of this | |
11 | .\" manual under the conditions for verbatim copying, provided that the | |
12 | .\" entire resulting derived work is distributed under the terms of a | |
13 | .\" permission notice identical to this one. | |
14 | .\" | |
15 | .\" Since the Linux kernel and libraries are constantly changing, this | |
16 | .\" manual page may be incorrect or out-of-date. The author(s) assume no | |
17 | .\" responsibility for errors or omissions, or for damages resulting from | |
18 | .\" the use of the information contained herein. The author(s) may not | |
19 | .\" have taken the same level of care in the production of this manual, | |
20 | .\" which is licensed free of charge, as they might when working | |
21 | .\" professionally. | |
22 | .\" | |
23 | .\" Formatted or processed versions of this manual, if unaccompanied by | |
24 | .\" the source, must acknowledge the copyright and authors of this work. | |
4b72fb64 | 25 | .\" %%%LICENSE_END |
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26 | .\" |
27 | .\" 2008-10-06, mtk: Created this as a new page by splitting | |
28 | .\" umount/umount2 material out of mount.2 | |
29 | .\" | |
4b8c67d9 | 30 | .TH UMOUNT 2 2017-09-15 "Linux" "Linux Programmer's Manual" |
5614f733 | 31 | .SH NAME |
9ee4a2b6 | 32 | umount, umount2 \- unmount filesystem |
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33 | .SH SYNOPSIS |
34 | .nf | |
35 | .B "#include <sys/mount.h>" | |
68e4db0a | 36 | .PP |
5614f733 | 37 | .BI "int umount(const char *" target ); |
68e4db0a | 38 | .PP |
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39 | .BI "int umount2(const char *" target ", int " flags ); |
40 | .fi | |
41 | .SH DESCRIPTION | |
42 | .BR umount () | |
43 | and | |
44 | .BR umount2 () | |
9ee4a2b6 | 45 | remove the attachment of the (topmost) filesystem mounted on |
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46 | .IR target . |
47 | .\" Note: the kernel naming differs from the glibc naming | |
48 | .\" umount2 is the glibc name for what the kernel now calls umount | |
49 | .\" and umount is the glibc name for oldumount | |
efeece04 | 50 | .PP |
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51 | Appropriate privilege (Linux: the |
52 | .B CAP_SYS_ADMIN | |
9ee4a2b6 | 53 | capability) is required to unmount filesystems. |
efeece04 | 54 | .PP |
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55 | Linux 2.1.116 added the |
56 | .BR umount2 () | |
57 | system call, which, like | |
58 | .BR umount (), | |
59 | unmounts a target, but allows additional | |
60 | .I flags | |
61 | controlling the behavior of the operation: | |
62 | .TP | |
63 | .BR MNT_FORCE " (since Linux 2.1.116)" | |
7045e438 | 64 | Ask the filesystem to abort pending requests before attempting the |
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65 | unmount. |
66 | This may allow the unmount to complete without waiting | |
67 | for an inaccessible server, but could cause data loss. | |
68 | If, after aborting requests, | |
69 | some processes still have active references to the filesystem, | |
70 | the unmount will still fail. | |
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71 | As at Linux 4.12, |
72 | .BR MNT_FORCE | |
73 | is supported only on the following filesystems: | |
74 | 9p (since Linux 2.6.16), | |
75 | ceph (since Linux 2.6.34), | |
76 | cifs (since Linux 2.6.12), | |
77 | fuse (since Linux 2.6.16), | |
78 | lustre (since Linux 3.11), | |
79 | and NFS (since Linux 2.1.116). | |
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80 | .TP |
81 | .BR MNT_DETACH " (since Linux 2.4.11)" | |
f1311221 EB |
82 | Perform a lazy unmount: make the mount point unavailable for new |
83 | accesses, immediately disconnect the filesystem and all filesystems | |
84 | mounted below it from each other and from the mount table, and | |
85 | actually perform the unmount when the mount point ceases to be busy. | |
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86 | .TP |
87 | .BR MNT_EXPIRE " (since Linux 2.6.8)" | |
88 | Mark the mount point as expired. | |
89 | If a mount point is not currently in use, then an initial call to | |
90 | .BR umount2 () | |
91 | with this flag fails with the error | |
92 | .BR EAGAIN , | |
93 | but marks the mount point as expired. | |
94 | The mount point remains expired as long as it isn't accessed | |
95 | by any process. | |
96 | A second | |
97 | .BR umount2 () | |
98 | call specifying | |
99 | .B MNT_EXPIRE | |
100 | unmounts an expired mount point. | |
101 | This flag cannot be specified with either | |
102 | .B MNT_FORCE | |
103 | or | |
104 | .BR MNT_DETACH . | |
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105 | .TP |
106 | .BR UMOUNT_NOFOLLOW " (since Linux 2.6.34)" | |
ab9cd9b7 | 107 | .\" Later added to 2.6.33-stable |
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108 | Don't dereference |
109 | .I target | |
110 | if it is a symbolic link. | |
60fe1ea1 | 111 | This flag allows security problems to be avoided in set-user-ID-\fIroot\fP |
9ee4a2b6 | 112 | programs that allow unprivileged users to unmount filesystems. |
47297adb | 113 | .SH RETURN VALUE |
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114 | On success, zero is returned. |
115 | On error, \-1 is returned, and | |
116 | .I errno | |
117 | is set appropriately. | |
118 | .SH ERRORS | |
9ee4a2b6 | 119 | The error values given below result from filesystem type independent |
5614f733 | 120 | errors. |
9ee4a2b6 | 121 | Each filesystem type may have its own special errors and its |
5614f733 | 122 | own special behavior. |
66a9882e | 123 | See the Linux kernel source code for details. |
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124 | .TP |
125 | .B EAGAIN | |
126 | A call to | |
127 | .BR umount2 () | |
128 | specifying | |
129 | .B MNT_EXPIRE | |
9ee4a2b6 | 130 | successfully marked an unbusy filesystem as expired. |
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131 | .TP |
132 | .B EBUSY | |
133 | .I target | |
134 | could not be unmounted because it is busy. | |
135 | .TP | |
136 | .B EFAULT | |
137 | .I target | |
138 | points outside the user address space. | |
139 | .TP | |
140 | .B EINVAL | |
141 | .I target | |
142 | is not a mount point. | |
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143 | .TP |
144 | .B EINVAL | |
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145 | .BR umount2 () |
146 | was called with | |
147 | .B MNT_EXPIRE | |
148 | and either | |
149 | .B MNT_DETACH | |
150 | or | |
151 | .BR MNT_FORCE . | |
152 | .TP | |
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153 | .BR EINVAL " (since Linux 2.6.34)" |
154 | .BR umount2 () | |
155 | was called with an invalid flag value in | |
156 | .IR flags . | |
157 | .TP | |
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158 | .B ENAMETOOLONG |
159 | A pathname was longer than | |
160 | .BR MAXPATHLEN . | |
161 | .TP | |
162 | .B ENOENT | |
163 | A pathname was empty or had a nonexistent component. | |
164 | .TP | |
165 | .B ENOMEM | |
166 | The kernel could not allocate a free page to copy filenames or data into. | |
167 | .TP | |
168 | .B EPERM | |
169 | The caller does not have the required privileges. | |
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170 | .SH VERSIONS |
171 | .BR MNT_DETACH | |
172 | and | |
173 | .BR MNT_EXPIRE | |
8749bd1a | 174 | .\" http://sourceware.org/bugzilla/show_bug.cgi?id=10092 |
33a0ccb2 | 175 | are available in glibc since version 2.11. |
47297adb | 176 | .SH CONFORMING TO |
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177 | These functions are Linux-specific and should not be used in |
178 | programs intended to be portable. | |
179 | .SH NOTES | |
b4bd5a5c | 180 | .SS umount() and shared mount points |
430a1677 | 181 | Shared mount points cause any mount activity on a mount point, including |
bf7bc8b8 | 182 | .BR umount () |
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183 | operations, to be forwarded to every shared mount point in the |
184 | peer group and every slave mount of that peer group. | |
185 | This means that | |
bf7bc8b8 | 186 | .BR umount () |
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187 | of any peer in a set of shared mounts will cause all of its |
188 | peers to be unmounted and all of their slaves to be unmounted as well. | |
efeece04 | 189 | .PP |
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190 | This propagation of unmount activity can be particularly surprising |
191 | on systems where every mount point is shared by default. | |
192 | On such systems, | |
193 | recursively bind mounting the root directory of the filesystem | |
194 | onto a subdirectory and then later unmounting that subdirectory with | |
195 | .BR MNT_DETACH | |
196 | will cause every mount in the mount namespace to be lazily unmounted. | |
efeece04 | 197 | .PP |
430a1677 | 198 | To ensure |
bf7bc8b8 | 199 | .BR umount () |
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200 | does not propagate in this fashion, |
201 | the mount point may be remounted using a | |
bf7bc8b8 | 202 | .BR mount () |
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203 | call with a |
204 | .I mount_flags | |
205 | argument that includes both | |
206 | .BR MS_REC | |
207 | and | |
208 | .BR MS_PRIVATE | |
209 | prior to | |
bf7bc8b8 | 210 | .BR umount () |
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211 | being called. |
212 | .SS Historical details | |
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213 | The original |
214 | .BR umount () | |
215 | function was called as \fIumount(device)\fP and would return | |
216 | .B ENOTBLK | |
217 | when called with something other than a block device. | |
23d35820 | 218 | In Linux 0.98p4, a call \fIumount(dir)\fP was added, in order to |
5614f733 | 219 | support anonymous devices. |
23d35820 | 220 | In Linux 2.3.99-pre7, the call \fIumount(device)\fP was removed, |
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221 | leaving only \fIumount(dir)\fP (since now devices can be mounted |
222 | in more than one place, so specifying the device does not suffice). | |
47297adb | 223 | .SH SEE ALSO |
5614f733 | 224 | .BR mount (2), |
a67271b0 | 225 | .BR mount_namespaces (7), |
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226 | .BR path_resolution (7), |
227 | .BR mount (8), | |
228 | .BR umount (8) |