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 .\" 3. 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
35 .Nd mount file systems
42 .Op Fl t Oo Cm no Oc Ns Cm Ar type Ns Op Cm , Ns Ar type ...
51 .Op Fl t Oo Cm no Oc Ns Cm Ar type Ns Op Cm , Ns Ar type ...
58 system call to prepare and graft a
60 device or the remote node (rhost:path) on to the file system tree at the point
66 are not provided, the appropriate information is taken from the
70 The system maintains a list of currently mounted file systems.
71 If no arguments are given to
75 The options are as follows:
76 .Bl -tag -width indent
80 in a selection of different human and machine readable formats.
83 for details on command line arguments.
85 All the file systems described in
88 Exceptions are those marked as
94 option was specified),
97 flag (see below), or if they are already mounted (except the
98 root file system which is always remounted to preserve
99 traditional single user mode behavior).
101 Causes everything to be done except for the actual system call.
102 This option is useful in conjunction with the
107 command is trying to do.
113 Forces the revocation of write access when trying to downgrade
114 a file system mount status from read-write to read-only.
116 forces the R/W mount of an unclean file system (dangerous; use with
119 When used in conjunction with the
123 those file systems which are marked as
126 When used in conjunction with the
128 option, also mount those file systems which are marked as
131 For compatibility with some other implementations, this flag is
134 Options are specified with a
136 flag followed by a comma separated string of options.
137 In case of conflicting options being specified, the rightmost option
139 The following options are available:
140 .Bl -tag -width indent
142 Enable POSIX.1e Access Control Lists, or ACLs, which can be customized via the
147 This flag is mutually exclusive with
151 All I/O to the file system should be done asynchronously.
154 flag to set, since it does not guarantee that the file system structure
155 on the disk will remain consistent.
158 flag should be used sparingly, and only when some data recovery
159 mechanism is present.
161 This flag indicates that the file system was mounted by
163 Automounted file systems are automatically unmounted by
166 Mount the file system read-write.
167 If that fails with an error that suggests that the media could be read-only,
168 then automatically try to mount the file system read-only.
172 flag, this is the same as specifying the options currently in effect for
173 the mounted file system.
175 Require that the mount point directory be empty.
179 forces the revocation of write access when trying to downgrade
180 a file system mount status from read-write to read-only.
182 forces the R/W mount of an unclean file system (dangerous; use with caution).
186 flag, this is the same as specifying all the options listed in the
188 file for the file system.
190 This file system should be skipped when
197 .It Cm mountprog Ns = Ns Aq Ar program
200 to use the specified program to mount the file system, instead of calling
205 mount -t foofs -o mountprog=/mydir/fooprog /dev/cd0 /mnt
208 Enable multi-label Mandatory Access Control, or MAC, on the specified file
210 If the file system supports multilabel operation, individual labels will
211 be maintained for each object in the file system, rather than using a
212 single label for all objects.
213 An alternative to the
219 for more information, which cause the multilabel mount flag to be set
220 automatically at mount-time.
222 Enable NFSv4 ACLs, which can be customized via the
227 This flag is mutually exclusive with
231 Metadata I/O should be done synchronously, while data I/O should be done
235 Do not update the file access time when reading from a file.
237 is useful on file systems where there are large numbers of files and
238 performance is more critical than updating the file access time (which is
239 rarely ever important).
240 This option is currently only supported on local file systems.
242 This file system should be skipped when
248 Disable read clustering.
250 Disable write clustering.
252 Do not mount if the requested mount point is already
253 the root of a mount point.
255 Do not allow execution of any binaries on the mounted file system.
256 This option is useful for a server that has file systems containing
257 binaries for architectures other than its own.
258 Note: This option was not designed as a security feature and no
259 guarantee is made that it will prevent malicious code execution; for
260 example, it is still possible to execute scripts which reside on a
264 Do not allow set-user-identifier or set-group-identifier bits to take effect.
265 Note: this option is worthless if a public available suid or sgid
266 wrapper is installed on your system.
267 It is set automatically when the user does not have super-user privileges.
269 Do not follow symlinks
270 on the mounted file system.
274 mount the file system read-only (even the super-user may not write it).
276 Take a snapshot of the specified filesystem.
277 When this option is used, all other options are ignored.
280 flag is required with this option.
282 Snapshot files must be created in the file system that is being
284 You may create up to 20 snapshots per file system.
285 Active snapshots are recorded in the superblock, so they persist across unmount
286 and remount operations and across system reboots.
287 When you are done with a snapshot, it can be removed with the
290 Snapshots may be removed in any order, however you may not get back all the
291 space contained in the snapshot as another snapshot may claim some of the blocks
292 that it is releasing.
293 Note that the schg flag is set on snapshots to ensure that not even the root
294 user can write to them.
295 The unlink command makes an exception for snapshot files in that it allows them
296 to be removed even though they have the schg flag set, so it is not necessary to
297 clear the schg flag before removing a snapshot file.
299 Once you have taken a snapshot, there are three interesting things that you can
306 on the snapshot file.
307 Assuming that the file system was clean when it was mounted, you should always
308 get a clean (and unchanging) result from running fsck on the snapshot.
309 This is essentially what the background fsck process does.
315 You will get a dump that is consistent with the file system as of the timestamp
319 Mount the snapshot as a frozen image of the file system.
320 To mount the snapshot
321 .Pa /var/snapshot/snap1 :
323 mdconfig -a -t vnode -f /var/snapshot/snap1 -u 4
324 mount -r /dev/md4 /mnt
327 You can now cruise around your frozen
331 Everything will be in the same state that it was at the time the snapshot was
333 The one exception is that any earlier snapshots will appear as zero length
335 When you are done with the mounted snapshot:
342 A directory on the mounted file system will respond to the SUID bit
343 being set, by setting the owner of any new files to be the same
344 as the owner of the directory.
345 New directories will inherit the bit from their parents.
346 Execute bits are removed from
347 the file, and it will not be given to root.
349 This feature is designed for use on fileservers serving PC users via
350 ftp, SAMBA, or netatalk.
351 It provides security holes for shell users and as
352 such should not be used on shell machines, especially on home directories.
353 This option requires the SUIDDIR
354 option in the kernel to work.
355 Only UFS file systems support this option.
358 for more information.
360 All I/O to the file system should be done synchronously.
364 indicate that the status of an already mounted file system should be changed.
366 Causes the namespace at the mount point to appear as the union
367 of the mounted file system root and the existing directory.
368 Lookups will be done in the mounted file system first.
369 If those operations fail due to a non-existent file the underlying
370 directory is then accessed.
371 All creates are done in the mounted file system.
373 The file system is untrusted and the kernel should use more
374 extensive checks on the file-system's metadata before using it.
375 This option is intended to be used when mounting file systems
376 from untrusted media such as USB memory sticks or other
377 externally-provided media.
380 Any additional options specific to a file system type that is not
381 one of the internally known types (see the
383 option) may be passed as a comma separated list; these options are
384 distinguished by a leading
390 .Bd -literal -offset indent
391 mount -t cd9660 -o -e /dev/cd0 /cdrom
396 to execute the equivalent of:
397 .Bd -literal -offset indent
398 /sbin/mount_cd9660 -e /dev/cd0 /cdrom
401 Options that take a value are specified using the -option=value syntax:
402 .Bd -literal -offset indent
403 mount -t msdosfs -o -u=fred,-g=wheel /dev/da0s1 /mnt
407 .Bd -literal -offset indent
408 /sbin/mount_msdosfs -u fred -g wheel /dev/da0s1 /mnt
411 Additional options specific to file system types
412 which are not internally known
413 (see the description of the
416 may be described in the manual pages for the associated
417 .Pa /sbin/mount_ Ns Sy XXX
420 Print mount information in
427 The file system is to be mounted read-only.
428 Mount the file system read-only (even the super-user may not write it).
434 .It Fl t Oo Cm no Oc Ns Cm Ar type Ns Op Cm , Ns Ar type ...
435 The argument following the
437 is used to indicate the file system type.
444 to indicate that the actions should only be taken on
445 file systems of the specified type.
446 More than one type may be specified in a comma separated list.
447 The list of file system types can be prefixed with
449 to specify the file system types for which action should
455 .Bd -literal -offset indent
456 mount -a -t nonfs,nullfs
459 mounts all file systems except those of type NFS and NULLFS.
461 The default behavior of
465 option directly to the
471 However, for the following file system types:
484 directly and will instead attempt to execute a program in
485 .Pa /sbin/mount_ Ns Ar type
488 is replaced by the file system type name.
491 file systems are mounted by the program
492 .Pa /sbin/mount_nfs .
494 Most file systems will be dynamically loaded by the kernel
495 if not already present, and if the kernel module is available.
499 flag indicates that the status of an already mounted file
500 system should be changed.
501 Any of the options discussed above (the
505 also a file system can be changed from read-only to read-write
507 An attempt to change from read-write to read-only will fail if any
508 files on the file system are currently open for writing unless the
510 flag is also specified.
511 The set of options is determined by applying the options specified
514 and finally applying the
523 is used alone, show all file systems, including those that were mounted with the
525 flag and show additional information about each file system (including fsid
528 The file system object is to be read and write.
531 .Bl -tag -width ".Ev PATH_FSTAB"
533 If the environment variable
535 is set, all operations are performed against the specified file.
537 will not be honored if the process environment or memory address space is
542 for more information.)
545 .Bl -tag -width /etc/fstab -compact
550 Various, most of them are self-explanatory.
552 .Dl XXXXX file system is not available
554 The kernel does not support the respective file system type.
556 support for a particular file system might be provided either on a static
557 (kernel compile-time), or dynamic basis (loaded as a kernel module by
565 .Xr xo_parse_args 3 ,
577 .Xr mount_msdosfs 8 ,
582 .Xr mount_unionfs 8 ,
594 the permissions on the original mount point determine if
596 is accessible from the mounted file system.
597 The minimum permissions for
598 the mount point for traversal across the mount point in both
599 directions to be possible for all users is 0111 (execute for all).
603 is preferred over the use of the file system specific
610 signal (that causes an update of the export list)
611 only when the file system is mounted via
614 It is possible for a corrupted file system to cause a crash.