1 .\" Copyright (c) 1980, 1989, 1991, 1993
2 .\" The Regents of the University of California. All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, are permitted provided that the following conditions
7 .\" 1. Redistributions of source code must retain the above copyright
8 .\" notice, this list of conditions and the following disclaimer.
9 .\" 2. Redistributions in binary form must reproduce the above copyright
10 .\" notice, this list of conditions and the following disclaimer in the
11 .\" documentation and/or other materials provided with the distribution.
12 .\" 4. Neither the name of the University nor the names of its contributors
13 .\" may be used to endorse or promote products derived from this software
14 .\" without specific prior written permission.
16 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
17 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
20 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 .\" @(#)mount.8 8.8 (Berkeley) 6/16/94
36 .Nd mount file systems
42 .Op Fl t Cm ufs | Ar external_type
49 .Op Fl t Cm ufs | Ar external_type
56 system call to prepare and graft a
58 device or the remote node (rhost:path) on to the file system tree at the point
64 are not provided, the appropriate information is taken from the
68 The system maintains a list of currently mounted file systems.
69 If no arguments are given to
73 The options are as follows:
74 .Bl -tag -width indent
76 All the file systems described in
79 Exceptions are those marked as
85 option was specified),
88 flag (see below), or if they are already mounted (except the
89 root file system which is always remounted to preserve
90 traditional single user mode behavior).
92 Causes everything to be done except for the actual system call.
93 This option is useful in conjunction with the
98 command is trying to do.
104 Forces the revocation of write access when trying to downgrade
105 a file system mount status from read-write to read-only.
107 forces the R/W mount of an unclean file system (dangerous; use with
110 When used in conjunction with the
112 option, also mount those file systems which are marked as
115 Options are specified with a
117 flag followed by a comma separated string of options.
118 In case of conflicting options being specified, the rightmost option
120 The following options are available:
121 .Bl -tag -width indent
123 Enable POSIX.1e Access Control Lists, or ACLs, which can be customized via the
128 This flag is mutually exclusive with
134 to the file system should be done asynchronously.
137 flag to set, since it does not guarantee that the file system structure
138 on the disk will remain consistent.
141 flag should be used sparingly, and only when some data recovery
142 mechanism is present.
146 flag, this is the same as specifying the options currently in effect for
147 the mounted file system.
149 If this option is specified,
151 will return 0 even if an error occurs
152 during the mount of the filesystem.
156 forces the revocation of write access when trying to downgrade
157 a file system mount status from read-write to read-only.
159 forces the R/W mount of an unclean file system (dangerous; use with caution).
163 flag, this is the same as specifying all the options listed in the
165 file for the file system.
167 This file system should be skipped when
174 .It Cm mountprog Ns = Ns Aq Ar program
177 to use the specified program to mount the file system, instead of calling
179 directly. For example:
181 mount -t foofs -o mountprog=/mydir/fooprog /dev/acd0 /mnt
184 Enable multi-label Mandatory Access Control, or MAC, on the specified file
186 If the file system supports multilabel operation, individual labels will
187 be maintained for each object in the file system, rather than using a
188 single label for all objects.
189 An alternative to the
195 for more information, which cause the multilabel mount flag to be set
196 automatically at mount-time.
198 Enable NFSv4 ACLs, which can be customized via the
203 This flag is mutually exclusive with
207 Metadata I/O should be done synchronously, while data I/O should be done
211 Do not update the file access time when reading from a file.
213 is useful on file systems where there are large numbers of files and
214 performance is more critical than updating the file access time (which is
215 rarely ever important).
216 This option is currently only supported on local file systems.
218 This file system should be skipped when
224 Disable read clustering.
226 Disable write clustering.
228 Do not allow execution of any binaries on the mounted file system.
229 This option is useful for a server that has file systems containing
230 binaries for architectures other than its own.
231 Note: This option was not designed as a security feature and no
232 guarantee is made that it will prevent malicious code execution; for
233 example, it is still possible to execute scripts which reside on a
237 Do not allow set-user-identifier or set-group-identifier bits to take effect.
238 Note: this option is worthless if a public available suid or sgid
241 is installed on your system.
242 It is set automatically when the user does not have super-user privileges.
244 Do not follow symlinks
245 on the mounted file system.
249 mount the file system read-only (even the super-user may not write it).
251 This option allows a snapshot of the specified file system to be taken.
254 flag is required with this option.
255 Note that snapshot files must be created in the file system that is being
257 You may create up to 20 snapshots per file system.
258 Active snapshots are recorded in the superblock, so they persist across unmount
259 and remount operations and across system reboots.
260 When you are done with a snapshot, it can be removed with the
263 Snapshots may be removed in any order, however you may not get back all the
264 space contained in the snapshot as another snapshot may claim some of the blocks
265 that it is releasing.
266 Note that the schg flag is set on snapshots to ensure that not even the root
267 user can write to them.
268 The unlink command makes an exception for snapshot files in that it allows them
269 to be removed even though they have the schg flag set, so it is not necessary to
270 clear the schg flag before removing a snapshot file.
272 Once you have taken a snapshot, there are three interesting things that you can
279 on the snapshot file.
280 Assuming that the file system was clean when it was mounted, you should always
281 get a clean (and unchanging) result from running fsck on the snapshot.
282 This is essentially what the background fsck process does.
288 You will get a dump that is consistent with the file system as of the timestamp
292 Mount the snapshot as a frozen image of the file system.
293 To mount the snapshot
294 .Pa /var/snapshot/snap1 :
296 mdconfig -a -t vnode -f /var/snapshot/snap1 -u 4
297 mount -r /dev/md4 /mnt
300 You can now cruise around your frozen
304 Everything will be in the same state that it was at the time the snapshot was
306 The one exception is that any earlier snapshots will appear as zero length
308 When you are done with the mounted snapshot:
315 A directory on the mounted file system will respond to the SUID bit
316 being set, by setting the owner of any new files to be the same
317 as the owner of the directory.
318 New directories will inherit the bit from their parents.
319 Execute bits are removed from
320 the file, and it will not be given to root.
322 This feature is designed for use on fileservers serving PC users via
323 ftp, SAMBA, or netatalk.
324 It provides security holes for shell users and as
325 such should not be used on shell machines, especially on home directories.
326 This option requires the SUIDDIR
327 option in the kernel to work.
328 Only UFS file systems support this option.
331 for more information.
335 to the file system should be done synchronously.
339 indicate that the status of an already mounted file system should be changed.
341 Causes the namespace at the mount point to appear as the union
342 of the mounted file system root and the existing directory.
343 Lookups will be done in the mounted file system first.
344 If those operations fail due to a non-existent file the underlying
345 directory is then accessed.
346 All creates are done in the mounted file system.
349 Any additional options specific to a file system type that is not
350 one of the internally known types (see the
352 option) may be passed as a comma separated list; these options are
353 distinguished by a leading
359 .Bd -literal -offset indent
360 mount -t cd9660 -o -e /dev/cd0 /cdrom
365 to execute the equivalent of:
366 .Bd -literal -offset indent
367 /sbin/mount_cd9660 -e /dev/cd0 /cdrom
370 Options that take a value are specified using the -option=value syntax:
371 .Bd -literal -offset indent
372 mount -t msdosfs -o -u=fred,-g=wheel /dev/da0s1 /mnt
376 .Bd -literal -offset indent
377 /sbin/mount_msdosfs -u fred -g wheel /dev/da0s1 /mnt
380 Additional options specific to file system types
381 which are not internally known
382 (see the description of the
385 may be described in the manual pages for the associated
386 .Pa /sbin/mount_ Ns Sy XXX
389 Print mount information in
396 The file system is to be mounted read-only.
397 Mount the file system read-only (even the super-user may not write it).
403 .It Fl t Cm ufs | Ar external_type
404 The argument following the
406 is used to indicate the file system type.
413 to indicate that the actions should only be taken on
414 file systems of the specified type.
415 More than one type may be specified in a comma separated list.
416 The list of file system types can be prefixed with
418 to specify the file system types for which action should
424 .Bd -literal -offset indent
425 mount -a -t nonfs,nullfs
428 mounts all file systems except those of type
433 The default behavior of
437 option directly to the
443 However, for the following file system types:
460 directly and will instead attempt to execute a program in
461 .Pa /sbin/mount_ Ns Sy XXX
464 is replaced by the file system type name.
465 For example, nfs file systems are mounted by the program
466 .Pa /sbin/mount_nfs .
468 Most file systems will be dynamically loaded by the kernel
469 if not already present, and if the kernel module is available.
473 flag indicates that the status of an already mounted file
474 system should be changed.
475 Any of the options discussed above (the
479 also a file system can be changed from read-only to read-write
481 An attempt to change from read-write to read-only will fail if any
482 files on the file system are currently open for writing unless the
484 flag is also specified.
485 The set of options is determined by applying the options specified
488 and finally applying the
497 is used alone, show all file systems, including those that were mounted with the
499 flag and show additional information about each file system (including fsid
502 The file system object is to be read and write.
505 .Bl -tag -width ".Ev PATH_FSTAB"
507 If the environment variable
509 is set, all operations are performed against the specified file.
511 will not be honored if the process environment or memory address space is
516 for more information.)
519 .Bl -tag -width /etc/fstab -compact
524 Various, most of them are self-explanatory.
526 .Dl XXXXX file system is not available
528 The kernel does not support the respective file system type.
530 support for a particular file system might be provided either on a static
531 (kernel compile-time), or dynamic basis (loaded as a kernel module by
545 .Xr mount_msdosfs 8 ,
550 .Xr mount_portalfs 8 ,
553 .Xr mount_unionfs 8 ,
560 the permissions on the original mount point determine if
562 is accessible from the mounted file system.
563 The minimum permissions for
564 the mount point for traversal across the mount point in both
565 directions to be possible for all users is 0111 (execute for all).
569 is preferred over the use of the file system specific
576 signal (that causes an update of the export list)
577 only when the file system is mounted via
585 It is possible for a corrupted file system to cause a crash.