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
114 those file systems which are marked as
117 When used in conjunction with the
119 option, also mount those file systems which are marked as
122 For compatibility with some other implementations, this flag is
125 Options are specified with a
127 flag followed by a comma separated string of options.
128 In case of conflicting options being specified, the rightmost option
130 The following options are available:
131 .Bl -tag -width indent
133 Enable POSIX.1e Access Control Lists, or ACLs, which can be customized via the
138 This flag is mutually exclusive with
144 to the file system should be done asynchronously.
147 flag to set, since it does not guarantee that the file system structure
148 on the disk will remain consistent.
151 flag should be used sparingly, and only when some data recovery
152 mechanism is present.
154 This flag indicates that the file system was mounted by
156 Automounted file systems are automatically unmounted by
161 flag, this is the same as specifying the options currently in effect for
162 the mounted file system.
166 forces the revocation of write access when trying to downgrade
167 a file system mount status from read-write to read-only.
169 forces the R/W mount of an unclean file system (dangerous; use with caution).
173 flag, this is the same as specifying all the options listed in the
175 file for the file system.
177 This file system should be skipped when
184 .It Cm mountprog Ns = Ns Aq Ar program
187 to use the specified program to mount the file system, instead of calling
192 mount -t foofs -o mountprog=/mydir/fooprog /dev/cd0 /mnt
195 Enable multi-label Mandatory Access Control, or MAC, on the specified file
197 If the file system supports multilabel operation, individual labels will
198 be maintained for each object in the file system, rather than using a
199 single label for all objects.
200 An alternative to the
206 for more information, which cause the multilabel mount flag to be set
207 automatically at mount-time.
209 Enable NFSv4 ACLs, which can be customized via the
214 This flag is mutually exclusive with
218 Metadata I/O should be done synchronously, while data I/O should be done
222 Do not update the file access time when reading from a file.
224 is useful on file systems where there are large numbers of files and
225 performance is more critical than updating the file access time (which is
226 rarely ever important).
227 This option is currently only supported on local file systems.
229 This file system should be skipped when
235 Disable read clustering.
237 Disable write clustering.
239 Do not allow execution of any binaries on the mounted file system.
240 This option is useful for a server that has file systems containing
241 binaries for architectures other than its own.
242 Note: This option was not designed as a security feature and no
243 guarantee is made that it will prevent malicious code execution; for
244 example, it is still possible to execute scripts which reside on a
248 Do not allow set-user-identifier or set-group-identifier bits to take effect.
249 Note: this option is worthless if a public available suid or sgid
252 is installed on your system.
253 It is set automatically when the user does not have super-user privileges.
255 Do not follow symlinks
256 on the mounted file system.
260 mount the file system read-only (even the super-user may not write it).
262 This option allows a snapshot of the specified file system to be taken.
265 flag is required with this option.
266 Note that snapshot files must be created in the file system that is being
268 You may create up to 20 snapshots per file system.
269 Active snapshots are recorded in the superblock, so they persist across unmount
270 and remount operations and across system reboots.
271 When you are done with a snapshot, it can be removed with the
274 Snapshots may be removed in any order, however you may not get back all the
275 space contained in the snapshot as another snapshot may claim some of the blocks
276 that it is releasing.
277 Note that the schg flag is set on snapshots to ensure that not even the root
278 user can write to them.
279 The unlink command makes an exception for snapshot files in that it allows them
280 to be removed even though they have the schg flag set, so it is not necessary to
281 clear the schg flag before removing a snapshot file.
283 Once you have taken a snapshot, there are three interesting things that you can
290 on the snapshot file.
291 Assuming that the file system was clean when it was mounted, you should always
292 get a clean (and unchanging) result from running fsck on the snapshot.
293 This is essentially what the background fsck process does.
299 You will get a dump that is consistent with the file system as of the timestamp
303 Mount the snapshot as a frozen image of the file system.
304 To mount the snapshot
305 .Pa /var/snapshot/snap1 :
307 mdconfig -a -t vnode -f /var/snapshot/snap1 -u 4
308 mount -r /dev/md4 /mnt
311 You can now cruise around your frozen
315 Everything will be in the same state that it was at the time the snapshot was
317 The one exception is that any earlier snapshots will appear as zero length
319 When you are done with the mounted snapshot:
326 A directory on the mounted file system will respond to the SUID bit
327 being set, by setting the owner of any new files to be the same
328 as the owner of the directory.
329 New directories will inherit the bit from their parents.
330 Execute bits are removed from
331 the file, and it will not be given to root.
333 This feature is designed for use on fileservers serving PC users via
334 ftp, SAMBA, or netatalk.
335 It provides security holes for shell users and as
336 such should not be used on shell machines, especially on home directories.
337 This option requires the SUIDDIR
338 option in the kernel to work.
339 Only UFS file systems support this option.
342 for more information.
346 to the file system should be done synchronously.
350 indicate that the status of an already mounted file system should be changed.
352 Causes the namespace at the mount point to appear as the union
353 of the mounted file system root and the existing directory.
354 Lookups will be done in the mounted file system first.
355 If those operations fail due to a non-existent file the underlying
356 directory is then accessed.
357 All creates are done in the mounted file system.
360 Any additional options specific to a file system type that is not
361 one of the internally known types (see the
363 option) may be passed as a comma separated list; these options are
364 distinguished by a leading
370 .Bd -literal -offset indent
371 mount -t cd9660 -o -e /dev/cd0 /cdrom
376 to execute the equivalent of:
377 .Bd -literal -offset indent
378 /sbin/mount_cd9660 -e /dev/cd0 /cdrom
381 Options that take a value are specified using the -option=value syntax:
382 .Bd -literal -offset indent
383 mount -t msdosfs -o -u=fred,-g=wheel /dev/da0s1 /mnt
387 .Bd -literal -offset indent
388 /sbin/mount_msdosfs -u fred -g wheel /dev/da0s1 /mnt
391 Additional options specific to file system types
392 which are not internally known
393 (see the description of the
396 may be described in the manual pages for the associated
397 .Pa /sbin/mount_ Ns Sy XXX
400 Print mount information in
407 The file system is to be mounted read-only.
408 Mount the file system read-only (even the super-user may not write it).
414 .It Fl t Cm ufs | Ar external_type
415 The argument following the
417 is used to indicate the file system type.
424 to indicate that the actions should only be taken on
425 file systems of the specified type.
426 More than one type may be specified in a comma separated list.
427 The list of file system types can be prefixed with
429 to specify the file system types for which action should
435 .Bd -literal -offset indent
436 mount -a -t nonfs,nullfs
439 mounts all file systems except those of type
444 The default behavior of
448 option directly to the
454 However, for the following file system types:
468 directly and will instead attempt to execute a program in
469 .Pa /sbin/mount_ Ns Sy XXX
472 is replaced by the file system type name.
473 For example, nfs file systems are mounted by the program
474 .Pa /sbin/mount_nfs .
476 Most file systems will be dynamically loaded by the kernel
477 if not already present, and if the kernel module is available.
481 flag indicates that the status of an already mounted file
482 system should be changed.
483 Any of the options discussed above (the
487 also a file system can be changed from read-only to read-write
489 An attempt to change from read-write to read-only will fail if any
490 files on the file system are currently open for writing unless the
492 flag is also specified.
493 The set of options is determined by applying the options specified
496 and finally applying the
505 is used alone, show all file systems, including those that were mounted with the
507 flag and show additional information about each file system (including fsid
510 The file system object is to be read and write.
513 .Bl -tag -width ".Ev PATH_FSTAB"
515 If the environment variable
517 is set, all operations are performed against the specified file.
519 will not be honored if the process environment or memory address space is
524 for more information.)
527 .Bl -tag -width /etc/fstab -compact
532 Various, most of them are self-explanatory.
534 .Dl XXXXX file system is not available
536 The kernel does not support the respective file system type.
538 support for a particular file system might be provided either on a static
539 (kernel compile-time), or dynamic basis (loaded as a kernel module by
555 .Xr mount_msdosfs 8 ,
560 .Xr mount_unionfs 8 ,
573 the permissions on the original mount point determine if
575 is accessible from the mounted file system.
576 The minimum permissions for
577 the mount point for traversal across the mount point in both
578 directions to be possible for all users is 0111 (execute for all).
582 is preferred over the use of the file system specific
589 signal (that causes an update of the export list)
590 only when the file system is mounted via
593 It is possible for a corrupted file system to cause a crash.