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28 .\" @(#)mount.8 8.8 (Berkeley) 6/16/94
29 .\" $FreeBSD: src/sbin/mount/mount.8,v 1.31.2.12 2003/02/23 21:17:42 trhodes Exp $
36 .Nd mount file systems
45 .Brq Ar special | node
56 system call to prepare and graft a
58 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 filesystems described in
79 Exceptions are those marked as
83 flag (see below), or if they are already mounted (except the
84 root filesystem which is always remounted to preserve
85 traditional single user mode behavior).
87 Causes everything to be done except for the actual system call.
88 This option is useful in conjunction with the
93 command is trying to do.
99 Forces the revocation of write access when trying to downgrade
100 a filesystem mount status from read-write to read-only.
102 forces the R/W mount of an unclean filesystem (dangerous; use with
105 Options are specified with a
107 flag followed by a comma separated string of options.
110 prefix is added or removed from a option name, then meaning is negated.
111 In case of conflicting options being specified, the rightmost option
113 The following options are available:
114 .Bl -tag -width indent
118 to the file system should be done asynchronously.
122 and should not be used unless you are prepared to recreate the file
123 system should your system crash.
127 flag, this is the same as specifying the options currently in effect for
128 the mounted filesystem.
132 forces the revocation of write access when trying to downgrade
133 a filesystem mount status from read-write to read-only.
135 forces the R/W mount of an unclean filesystem (dangerous; use with caution).
139 flag, this is the same as specifying all the options listed in the
141 file for the filesystem.
143 Metadata I/O should be done synchronously, while data I/O should be done
147 Do not update the file access time when reading from a file.
149 is useful on filesystems where there are large numbers of files and
150 performance is more critical than updating the file access time (which is
151 rarely ever important).
152 This option is currently only supported on local filesystems.
154 This filesystem should be skipped when
160 Disable read clustering.
162 Disable write clustering.
164 Do not interpret character or block special devices on the file system.
165 This option is useful for a server that has file systems containing
166 special devices for architectures other than its own.
167 This option is set automatically when the user does not have super-user
170 Do not allow execution of any binaries on the mounted file system.
171 This option is useful for a server that has file systems containing
172 binaries for architectures other than its own.
174 Do not allow set-user-identifier or set-group-identifier bits to take effect.
175 Note: this option is worthless if a public available suid or sgid
178 is installed on your system.
179 It is set automatically when the user does not have super-user privileges.
181 Do not follow symlinks
182 on the mounted file system.
183 .It Cm rdonly , ro , norw
186 mount the file system read-only (even the super-user may not write it).
190 to the file system should be done synchronously.
192 If the device supports TRIM
193 .Va ( kern.cam.da.X.trim_enabled
195 the file system will perform online trim for corresponding block deletions.
198 supports this feature.
200 A directory on the mounted filesystem will respond to the SUID bit
201 being set, by setting the owner of any new files to be the same
202 as the owner of the directory.
203 New directories will inherit the bit from their parents.
204 Execute bits are removed from
205 the file, and it will not be given to root.
207 This feature is designed for use on fileservers serving PC users via
209 It provides security holes for shell users and as
210 such should not be used on shell machines, especially on home directories.
211 This option requires the SUIDDIR
212 option in the kernel to work.
215 filesystems support this option.
218 for more information.
222 indicate that the status of an already mounted file system should be changed.
224 Causes the namespace at the mount point to appear as the union
225 of the mounted filesystem root and the existing directory.
226 Lookups will be done in the mounted filesystem first.
227 If those operations fail due to a non-existent file the underlying
228 directory is then accessed.
229 All creates are done in the mounted filesystem.
235 Any additional options specific to a filesystem type that is not
236 one of the internally known types (see the
238 option) may be passed as a comma separated list; these options are
239 distinguished by a leading
242 Options that take a value are specified using the syntax -option=value.
246 .Bd -literal -offset indent
247 mount -t mfs -o nosuid,-N,-s=4000 /dev/da0s0b /tmp
252 to execute the equivalent of:
253 .Bd -literal -offset indent
254 /sbin/mount_mfs -o nosuid -N -s 4000 /dev/da0s0b /tmp
257 Additional options specific to filesystem types
258 which are not internally known
259 (see the description of the
262 may be described in the manual pages for the associated
263 .Pa /sbin/mount_ Ns Sy XXX
266 Print mount information in
269 If fstab is missing or if the freq and passno fields are omitted,
270 the default values as described in
277 The file system is to be mounted read-only.
278 Mount the file system read-only (even the super-user may not write it).
285 The argument following the
287 is used to indicate the file system type.
294 to indicate that the actions should only be taken on
295 filesystems of the specified type.
296 More than one type may be specified in a comma separated list.
297 The list of filesystem types can be prefixed with
299 to specify the filesystem types for which action should
305 .Bd -literal -offset indent
306 mount -a -t nonfs,mfs
309 mounts all filesystems except those of type
314 If the type is not the internally known type,
317 will attempt to execute a program in
318 .Pa /sbin/mount_ Ns Sy XXX
321 is replaced by the type name.
322 For example, nfs filesystems are mounted by the program
323 .Pa /sbin/mount_nfs .
325 Most filesystems will be dynamically loaded by their
328 if not already present in the kernel, using the
331 Because this mechanism requires writable temporary space,
332 the filesystem type containing
334 must be compiled into the kernel, and the filesystems containing
340 before any filesystems which might be dynamically loaded.
344 flag indicates that the status of an already mounted file
345 system should be changed.
346 Any of the options discussed above (the
350 also a file system can be changed from read-only to read-write
352 An attempt to change from read-write to read-only will fail if any
353 files on the filesystem are currently open for writing unless the
355 flag is also specified.
356 The set of options is determined by applying the options specified
359 and finally applying the
367 The file system object is to be read and write.
370 .Bl -tag -width PATH_FSTAB
372 If the environment variable
374 is set all operations are performed against the specified file.
377 .Bl -tag -width /etc/fstab -compact
382 Various, most of them are self-explanatory.
384 .Dl XXXXX filesystem is not available
386 The kernel does not support the respective filesystem type.
388 support for a particular filesystem might be provided either on a static
389 (kernel compile-time), or dynamic basis (loaded as a kernel module by
393 or its subprocesses attempt to dynamically load a filesystem module if
394 it has not been configured statically, using
396 In this case, the above error message can also mean that you did not
397 have permission to load the module.
413 .Xr mount_linprocfs 8 ,
436 the permissions on the original mount point determine if
438 is accessible from the mounted file system.
439 The minimum permissions for
440 the mount point for traversal across the mount point in both
441 directions to be possible for all users is 0111 (execute for all).
443 It is possible for a corrupted file system to cause a crash.