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28 .\" @(#)mount.2 8.3 (Berkeley) 5/24/95
38 .Nd mount or dismount a file system
45 .Fn mount "const char *type" "const char *dir" "int flags" "void *data"
47 .Fn unmount "const char *dir" "int flags"
50 .Fn nmount "struct iovec *iov" "u_int niov" "int flags"
55 a file system object onto the system file tree
60 describes the file system object to be mounted.
63 tells the kernel how to interpret
68 The contents of the file system
69 become available through the new mount point
74 of a successful mount are swept under the carpet so to speak, and
75 are unavailable until the file system is unmounted.
79 system call behaves similarly to
81 except that the mount options (file system type name, device to mount,
82 mount-point name, etc.) are passed as an array of name-value pairs
88 The following options are required by all file systems:
89 .Bl -column fstype -offset indent
91 .Li fstype Ta file system type name (e.g., Dq Li procfs )
93 .Li fspath Ta mount point pathname (e.g., Dq Li /proc )
96 Depending on the file system type, other options may be
97 recognized or required;
98 for example, most disk-based file systems require a
100 option containing the pathname of a special device
101 in addition to the options listed above.
103 By default only the super-user may call the
106 This restriction can be removed by setting the
110 to a non-zero value; see the BUGS section for more information.
115 suppress default semantics which affect file system access.
116 .Bl -tag -width MNT_SYNCHRONOUS
118 The file system should be treated as read-only;
119 even the super-user may not write on it.
120 Specifying MNT_UPDATE without this option will upgrade
121 a read-only file system to read/write.
123 Do not allow files to be executed from the file system.
125 Do not honor setuid or setgid bits on files when executing them.
126 This flag is set automatically when the caller is not the super-user.
128 Disable update of file access times.
130 Create a snapshot of the file system.
131 This is currently only supported on UFS2 file systems, see
133 for more information.
135 Directories with the SUID bit set chown new files to their own owner.
136 This flag requires the SUIDDIR option to have been compiled into the kernel
142 pages for more information.
143 .It Dv MNT_SYNCHRONOUS
144 All I/O to the file system should be done synchronously.
146 All I/O to the file system should be done asynchronously.
148 Force a read-write mount even if the file system appears to be unclean.
154 specify that the file system is to be forcibly downgraded to a read-only
155 mount even if some files are open for writing.
156 .It Dv MNT_NOCLUSTERR
157 Disable read clustering.
158 .It Dv MNT_NOCLUSTERW
159 Disable write clustering.
161 Do not mount over the root of another mount point.
163 Require an empty directory for the mount point directory.
168 indicates that the mount command is being applied
169 to an already mounted file system.
170 This allows the mount flags to be changed without requiring
171 that the file system be unmounted and remounted.
172 Some file systems may not allow all flags to be changed.
174 many file systems will not allow a change from read-write to read-only.
178 causes the vfs subsystem to update its data structures pertaining to
179 the specified already mounted file system.
183 argument names the file system.
184 The types of file systems known to the system can be obtained with
190 is a pointer to a structure that contains the type
191 specific arguments to mount.
192 The format for these argument structures is described in the
193 manual page for each file system.
194 By convention file system manual pages are named
195 by prefixing ``mount_'' to the name of the file system as returned by
199 file system is described by the
202 It should be noted that a manual page for default
203 file systems, known as UFS and UFS2, does not exist.
207 system call disassociates the file system from the specified
215 to specify that the file system should be forcibly unmounted
216 even if files are still active.
217 Active special devices continue to work,
218 but any further accesses to any other active files result in errors
219 even if the file system is later remounted.
225 should instead be a file system ID encoded as
226 .Dq Li FSID : Ns Ar val0 : Ns Ar val1 ,
231 are the contents of the
235 The file system that has the specified file system ID will be unmounted.
243 system calls will fail when one of the following occurs:
246 The caller is neither the super-user nor the owner of
248 .It Bq Er ENAMETOOLONG
249 A component of a pathname exceeded 255 characters,
250 or the entire length of a path name exceeded 1023 characters.
252 Too many symbolic links were encountered in translating a pathname.
265 Another process currently holds a reference to
270 option was given, and the requested mount point
271 is already the root of another mount point.
276 points outside the process's allocated address space.
278 An I/O error occurred while reading data from
281 The backing store for
283 detected corrupted data while reading.
286 The following errors can occur for a
291 A component of ufs_args
298 is not a block device.
302 option was specified, and the requested mount point
303 is not an empty directory.
305 The major device number of
307 is out of range (this indicates no device driver exists
308 for the associated hardware).
313 No space remains in the mount table.
315 The super block for the file system had a bad magic
316 number or an out of range block size.
318 The super block for the file system had a bad check hash.
319 The check hash can usually be corrected by running
322 Not enough memory was available to read the cylinder
323 group information for the file system.
325 An I/O error occurred while reading the super block or
326 cylinder group information.
331 points outside the process's allocated address space.
334 The following errors can occur for a
340 timed out trying to contact the server.
342 Some part of the information described by nfs_args
343 points outside the process's allocated address space.
348 system call may fail with one of the following errors:
351 The caller is neither the super-user nor the user who issued the corresponding
354 .It Bq Er ENAMETOOLONG
355 The length of the path name exceeded 1023 characters.
357 The requested directory is not in the mount table.
359 The file system ID specified using
361 was not found in the mount table.
363 The file system ID specified using
365 could not be decoded.
367 The specified file system is the root file system.
369 A process is holding a reference to a file located
372 An I/O error occurred while writing cached file system information.
377 points outside the process's allocated address space.
389 functions appeared in
393 system call first appeared in
396 Some of the error codes need translation to more obvious messages.
398 Allowing untrusted users to mount arbitrary media, e.g. by enabling
400 should not be considered safe.
403 were not built to safeguard against malicious devices.