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28 .\" @(#)mount.2 8.3 (Berkeley) 5/24/95
29 .\" $FreeBSD: src/lib/libc/sys/mount.2,v 1.20.2.8 2003/01/17 22:02:42 joerg Exp $
37 .Nd mount or dismount a filesystem
44 .Fn mount "const char *type" "const char *dir" "int flags" "void *data"
46 .Fn unmount "const char *dir" "int flags"
51 a filesystem object onto the system file tree
56 describes the filesystem object to be mounted.
59 tells the kernel how to interpret
64 The contents of the filesystem
65 become available through the new mount point
70 of a successful mount are swept under the carpet so to speak, and
71 are unavailable until the filesystem is unmounted.
73 By default only the super-user may call the
76 This restriction can be removed by setting the sysctl
83 suppress default semantics which affect filesystem access.
84 .Bl -tag -width ".Dv MNT_SYNCHRONOUS"
86 The filesystem should be treated as read-only;
87 Even the super-user may not write on it.
90 without this option will upgrade a read-only filesystem to read/write.
92 Do not allow files to be executed from the filesystem.
94 Do not honor setuid or setgid bits on files when executing them.
95 This flag is set automatically when the caller is not the super-user.
97 Disable update of file access times.
99 Do not interpret special files on the filesystem.
100 This flag is set automatically when the caller is not the super-user.
102 Directories with the SUID bit set chown new files to their own owner.
103 .It Dv MNT_SYNCHRONOUS
104 All I/O to the filesystem should be done synchronously.
106 All I/O to the filesystem should be done asynchronously.
108 Force a read-write mount even if the filesystem appears to be unclean.
110 .It Dv MNT_NOCLUSTERR
111 Disable read clustering.
112 .It Dv MNT_NOCLUSTERW
113 Disable write clustering.
118 indicates that the mount command is being applied
119 to an already mounted filesystem.
120 This allows the mount flags to be changed without requiring
121 that the filesystem be unmounted and remounted.
122 Some filesystems may not allow all flags to be changed.
124 many filesystems will not allow a change from read-write to read-only.
128 causes the vfs subsystem to update its data structures pertaining to
129 the specified already mounted filesystem.
133 argument names the filesystem.
134 The types of filesystems known to the system can be obtained with
138 is a pointer to a structure that contains the type
139 specific arguments to mount.
140 The format for these argument structures is described in the
141 manual page for each filesystem.
142 By convention filesystem manual pages are named
143 by prefixing ``mount_'' to the name of the filesystem as returned by
147 filesystem is described by the
153 function call disassociates the filesystem from the specified
161 to specify that the filesystem should be forcibly unmounted or made read-only
166 are also specified) even if files are still active.
167 Active special devices continue to work,
168 but any further accesses to any other active files result in errors
169 even if the filesystem is later remounted.
173 option requires the SUIDDIR option to have been compiled into the kernel
179 pages for more information.
185 function will fail when one of the following occurs:
188 The caller is neither the super-user nor the owner of
192 belongs to a filesystem that does not support stacked mounts.
193 .It Bq Er ENAMETOOLONG
194 A component of a pathname exceeded 255 characters,
195 or the entire length of a path name exceeded 1023 characters.
197 Too many symbolic links were encountered in translating a pathname.
210 Another process currently holds a reference to
214 points outside the process's allocated address space.
217 The following errors can occur for a
222 A component of ufs_args
227 is not a block device.
229 The major device number of
231 is out of range (this indicates no device driver exists
232 for the associated hardware).
237 No space remains in the mount table.
239 The super block for the filesystem had a bad magic
240 number or an out of range block size.
242 Not enough memory was available to read the cylinder
243 group information for the filesystem.
245 An I/O error occurred while reading the super block or
246 cylinder group information.
249 points outside the process's allocated address space.
252 The following errors can occur for a
258 timed out trying to contact the server.
260 Some part of the information described by nfs_args
261 points outside the process's allocated address space.
264 The following errors can occur for a
269 No space remains in the mount table.
271 The super block for the filesystem had a bad magic
272 number or an out of range block size.
274 Not enough memory was available to read the cylinder
275 group information for the filesystem.
277 A paging error occurred while reading the super block or
278 cylinder group information.
281 points outside the process's allocated address space.
286 function may fail with one of the following errors:
289 The caller is neither the super-user nor the user who issued the corresponding
293 A component of the path is not a directory.
294 .It Bq Er ENAMETOOLONG
295 A component of a pathname exceeded 255 characters,
296 or an entire path name exceeded 1023 characters.
298 Too many symbolic links were encountered in translating the pathname.
300 The requested directory is not in the mount table.
302 A process is holding a reference to a file located
305 An I/O error occurred while writing cached filesystem information.
308 points outside the process's allocated address space.
315 mount can also fail if the maximum number of filesystems are currently
328 function calls appeared in
331 Some of the error codes need translation to more obvious messages.