summaryrefslogtreecommitdiffstats
path: root/lib/libc/sys/mount.2
blob: 58094f2d9e834078d22fb958106504f4dcb37f63 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
.\" Copyright (c) 1980, 1989, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     @(#)mount.2	8.3 (Berkeley) 5/24/95
.\" $FreeBSD$
.\"
.Dd September 8, 2003
.Dt MOUNT 2
.Os
.Sh NAME
.Nm mount ,
.Nm unmount
.Nd mount or dismount a file system
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/param.h
.In sys/mount.h
.Ft int
.Fn mount "const char *type" "const char *dir" "int flags" "void *data"
.Ft int
.Fn unmount "const char *dir" "int flags"
.Sh DESCRIPTION
The
.Fn mount
system call grafts
a file system object onto the system file tree
at the point
.Fa dir .
The argument
.Fa data
describes the file system object to be mounted.
The argument
.Fa type
tells the kernel how to interpret
.Fa data
(See
.Fa type
below).
The contents of the file system
become available through the new mount point
.Fa dir .
Any files in
.Fa dir
at the time
of a successful mount are swept under the carpet so to speak, and
are unavailable until the file system is unmounted.
.Pp
By default only the super-user may call the
.Fn mount
system call.
This restriction can be removed by setting the
.Va vfs.usermount
.Xr sysctl 8
variable
to a non-zero value.
.Pp
The following
.Fa flags
may be specified to
suppress default semantics which affect file system access.
.Bl -tag -width MNT_SYNCHRONOUS
.It Dv MNT_RDONLY
The file system should be treated as read-only;
even the super-user may not write on it.
Specifying MNT_UPDATE without this option will upgrade
a read-only file system to read/write.
.It Dv MNT_NOEXEC
Do not allow files to be executed from the file system.
.It Dv MNT_NOSUID
Do not honor setuid or setgid bits on files when executing them.
This flag is set automatically when the caller is not the super-user.
.It Dv MNT_NOATIME
Disable update of file access times.
.It Dv MNT_NODEV
Do not interpret special files on the file system.
This flag is set automatically when the caller is not the super-user.
.It Dv MNT_SUIDDIR
Directories with the SUID bit set chown new files to their own owner.
This flag requires the SUIDDIR option to have been compiled into the kernel
to have any effect.
See the
.Xr mount 8
and
.Xr chmod 2
pages for more information.
.It Dv MNT_SYNCHRONOUS
All I/O to the file system should be done synchronously.
.It Dv MNT_ASYNC
All I/O to the file system should be done asynchronously.
.It Dv MNT_FORCE
Force a read-write mount even if the file system appears to be unclean.
Dangerous.
Together with
.Dv MNT_UPDATE
and
.Dv MNT_RDONLY ,
specify that the file system is to be forcibly downgraded to a read-only
mount even if some files are open for writing.
.It Dv MNT_NOCLUSTERR
Disable read clustering.
.It Dv MNT_NOCLUSTERW
Disable write clustering.
.El
.Pp
The flag
.Dv MNT_UPDATE
indicates that the mount command is being applied
to an already mounted file system.
This allows the mount flags to be changed without requiring
that the file system be unmounted and remounted.
Some file systems may not allow all flags to be changed.
For example,
many file systems will not allow a change from read-write to read-only.
.Pp
The flag
.Dv MNT_RELOAD
causes the vfs subsystem to update its data structures pertaining to
the specified already mounted file system.
.Pp
The
.Fa type
argument names the file system.
The types of file systems known to the system can be obtained with
.Xr lsvfs 1 .
.Pp
The
.Fa data
argument
is a pointer to a structure that contains the type
specific arguments to mount.
The format for these argument structures is described in the
manual page for each file system.
By convention file system manual pages are named
by prefixing ``mount_'' to the name of the file system as returned by
.Xr lsvfs 1 .
Thus the
.Tn NFS
file system is described by the
.Xr mount_nfs 8
manual page.
.Pp
The
.Fn unmount
system call disassociates the file system from the specified
mount point
.Fa dir .
.Pp
The
.Fa flags
argument may include
.Dv MNT_FORCE
to specify that the file system should be forcibly unmounted
even if files are still active.
Active special devices continue to work,
but any further accesses to any other active files result in errors
even if the file system is later remounted.
.Pp
If the
.Dv MNT_BYFSID
flag is specified,
.Fa dir
should instead be a file system ID encoded as
.Dq Li FSID : Ns Ar val0 : Ns Ar val1 ,
where
.Ar val0
and
.Ar val1
are the contents of the
.Vt fsid_t
.Va val[]
array in decimal.
The file system that has the specified file system ID will be unmounted.
.Sh RETURN VALUES
.Rv -std
.Sh ERRORS
The
.Fn mount
system call will fail when one of the following occurs:
.Bl -tag -width Er
.It Bq Er EPERM
The caller is neither the super-user nor the owner of
.Fa dir .
.It Bq Er ENAMETOOLONG
A component of a pathname exceeded 255 characters,
or the entire length of a path name exceeded 1023 characters.
.It Bq Er ELOOP
Too many symbolic links were encountered in translating a pathname.
.It Bq Er ENOENT
A component of
.Fa dir
does not exist.
.It Bq Er ENOTDIR
A component of
.Fa name
is not a directory,
or a path prefix of
.Fa special
is not a directory.
.It Bq Er EBUSY
Another process currently holds a reference to
.Fa dir .
.It Bq Er EFAULT
The
.Fa dir
argument
points outside the process's allocated address space.
.El
.Pp
The following errors can occur for a
.Em ufs
file system mount:
.Bl -tag -width Er
.It Bq Er ENODEV
A component of ufs_args
.Fa fspec
does not exist.
.It Bq Er ENOTBLK
The
.Fa fspec
argument
is not a block device.
.It Bq Er ENXIO
The major device number of
.Fa fspec
is out of range (this indicates no device driver exists
for the associated hardware).
.It Bq Er EBUSY
.Fa fspec
is already mounted.
.It Bq Er EMFILE
No space remains in the mount table.
.It Bq Er EINVAL
The super block for the file system had a bad magic
number or an out of range block size.
.It Bq Er ENOMEM
Not enough memory was available to read the cylinder
group information for the file system.
.It Bq Er EIO
An I/O error occurred while reading the super block or
cylinder group information.
.It Bq Er EFAULT
The
.Fa fspec
argument
points outside the process's allocated address space.
.El
.Pp
The following errors can occur for a
.Em nfs
file system mount:
.Bl -tag -width Er
.It Bq Er ETIMEDOUT
.Em Nfs
timed out trying to contact the server.
.It Bq Er EFAULT
Some part of the information described by nfs_args
points outside the process's allocated address space.
.El
.Pp
The
.Fn unmount
system call may fail with one of the following errors:
.Bl -tag -width Er
.It Bq Er EPERM
The caller is neither the super-user nor the user who issued the corresponding
.Fn mount
call.
.It Bq Er ENAMETOOLONG
The length of the path name exceeded 1023 characters.
.It Bq Er EINVAL
The requested directory is not in the mount table.
.It Bq Er ENOENT
The file system ID specified using
.Dv MNT_BYFSID
was not found in the mount table.
.It Bq Er EINVAL
The file system ID specified using
.Dv MNT_BYFSID
could not be decoded.
.It Bq Er EINVAL
The specified file system is the root file system.
.It Bq Er EBUSY
A process is holding a reference to a file located
on the file system.
.It Bq Er EIO
An I/O error occurred while writing cached file system information.
.It Bq Er EFAULT
The
.Fa dir
argument
points outside the process's allocated address space.
.El
.Pp
A
.Em ufs
mount can also fail if the maximum number of file systems are currently
mounted.
.Sh SEE ALSO
.Xr lsvfs 1 ,
.Xr mount 8 ,
.Xr umount 8
.Sh BUGS
Some of the error codes need translation to more obvious messages.
.Sh HISTORY
The
.Fn mount
and
.Fn unmount
functions appeared in
.At v6 .
OpenPOWER on IntegriCloud