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35 .Nd mount or dismount a file system
42 .Fn mount "const char *type" "const char *dir" "int flags" "void *data"
44 .Fn unmount "const char *dir" "int flags"
47 .Fn nmount "struct iovec *iov" "u_int niov" "int flags"
52 a file system object onto the system file tree
57 describes the file system object to be mounted.
60 tells the kernel how to interpret
65 The contents of the file system
66 become available through the new mount point
71 of a successful mount are swept under the carpet so to speak, and
72 are unavailable until the file system is unmounted.
76 system call behaves similarly to
78 except that the mount options (file system type name, device to mount,
79 mount-point name, etc.) are passed as an array of name-value pairs
85 The following options are required by all file systems:
86 .Bl -column fstype -offset indent
88 .Li fstype Ta file system type name (e.g., Dq Li procfs )
90 .Li fspath Ta mount point pathname (e.g., Dq Li /proc )
93 Depending on the file system type, other options may be
94 recognized or required;
95 for example, most disk-based file systems require a
97 option containing the pathname of a special device
98 in addition to the options listed above.
100 By default only the super-user may call the
103 This restriction can be removed by setting the
107 to a non-zero value; see the BUGS section for more information.
112 suppress default semantics which affect file system access.
113 .Bl -tag -width MNT_SYNCHRONOUS
115 The file system should be treated as read-only;
116 even the super-user may not write on it.
117 Specifying MNT_UPDATE without this option will upgrade
118 a read-only file system to read/write.
120 Do not allow files to be executed from the file system.
122 Do not honor setuid or setgid bits on files when executing them.
123 This flag is set automatically when the caller is not the super-user.
125 Disable update of file access times.
127 Create a snapshot of the file system.
128 This is currently only supported on UFS2 file systems, see
130 for more information.
132 Directories with the SUID bit set chown new files to their own owner.
133 This flag requires the SUIDDIR option to have been compiled into the kernel
139 pages for more information.
140 .It Dv MNT_SYNCHRONOUS
141 All I/O to the file system should be done synchronously.
143 All I/O to the file system should be done asynchronously.
145 Force a read-write mount even if the file system appears to be unclean.
151 specify that the file system is to be forcibly downgraded to a read-only
152 mount even if some files are open for writing.
153 .It Dv MNT_NOCLUSTERR
154 Disable read clustering.
155 .It Dv MNT_NOCLUSTERW
156 Disable write clustering.
158 Do not mount over the root of another mount point.
160 Require an empty directory for the mount point directory.
165 indicates that the mount command is being applied
166 to an already mounted file system.
167 This allows the mount flags to be changed without requiring
168 that the file system be unmounted and remounted.
169 Some file systems may not allow all flags to be changed.
171 many file systems will not allow a change from read-write to read-only.
175 causes the vfs subsystem to update its data structures pertaining to
176 the specified already mounted file system.
180 argument names the file system.
181 The types of file systems known to the system can be obtained with
187 is a pointer to a structure that contains the type
188 specific arguments to mount.
189 The format for these argument structures is described in the
190 manual page for each file system.
191 By convention file system manual pages are named
192 by prefixing ``mount_'' to the name of the file system as returned by
196 file system is described by the
199 It should be noted that a manual page for default
200 file systems, known as UFS and UFS2, does not exist.
204 system call disassociates the file system from the specified
212 to specify that the file system should be forcibly unmounted
213 even if files are still active.
214 Active special devices continue to work,
215 but any further accesses to any other active files result in errors
216 even if the file system is later remounted.
222 should instead be a file system ID encoded as
223 .Dq Li FSID : Ns Ar val0 : Ns Ar val1 ,
228 are the contents of the
232 The file system that has the specified file system ID will be unmounted.
240 system calls will fail when one of the following occurs:
243 The caller is neither the super-user nor the owner of
245 .It Bq Er ENAMETOOLONG
246 A component of a pathname exceeded 255 characters,
247 or the entire length of a path name exceeded 1023 characters.
249 Too many symbolic links were encountered in translating a pathname.
262 Another process currently holds a reference to
267 option was given, and the requested mount point
268 is already the root of another mount point.
273 points outside the process's allocated address space.
275 An I/O error occurred while reading data from
278 The backing store for
280 detected corrupted data while reading.
283 The following errors can occur for a
288 A component of ufs_args
295 is not a block device.
299 option was specified, and the requested mount point
300 is not an empty directory.
302 The major device number of
304 is out of range (this indicates no device driver exists
305 for the associated hardware).
310 No space remains in the mount table.
312 The super block for the file system had a bad magic
313 number or an out of range block size.
315 The super block for the file system had a bad check hash.
316 The check hash can usually be corrected by running
319 Not enough memory was available to read the cylinder
320 group information for the file system.
322 An I/O error occurred while reading the super block or
323 cylinder group information.
328 points outside the process's allocated address space.
331 The following errors can occur for a
337 timed out trying to contact the server.
339 Some part of the information described by nfs_args
340 points outside the process's allocated address space.
345 system call may fail with one of the following errors:
348 The caller is neither the super-user nor the user who issued the corresponding
351 .It Bq Er ENAMETOOLONG
352 The length of the path name exceeded 1023 characters.
354 The requested directory is not in the mount table.
356 The file system ID specified using
358 was not found in the mount table.
360 The file system ID specified using
362 could not be decoded.
364 The specified file system is the root file system.
366 A process is holding a reference to a file located
369 An I/O error occurred while writing cached file system information.
374 points outside the process's allocated address space.
386 functions appeared in
390 system call first appeared in
393 Some of the error codes need translation to more obvious messages.
395 Allowing untrusted users to mount arbitrary media, e.g. by enabling
397 should not be considered safe.
400 were not built to safeguard against malicious devices.