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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 $
30 .\" $DragonFly: src/lib/libc/sys/mount.2,v 1.6 2008/02/09 00:10:29 swildner Exp $
38 .Nd mount or dismount a filesystem
45 .Fn mount "const char *type" "const char *dir" "int flags" "void *data"
47 .Fn unmount "const char *dir" "int flags"
52 a filesystem object onto the system file tree
57 describes the filesystem object to be mounted.
60 tells the kernel how to interpret
65 The contents of the filesystem
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 filesystem is unmounted.
74 By default only the super-user may call the
77 This restriction can be removed by setting the sysctl
84 suppress default semantics which affect filesystem access.
85 .Bl -tag -width MNT_SYNCHRONOUS
87 The filesystem should be treated as read-only;
88 Even the super-user may not write on it.
89 Specifying MNT_UPDATE without this option will upgrade
90 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
162 (if MNT_UPDATE and MNT_RDONLY are also specified)
163 even if files are still active.
164 Active special devices continue to work,
165 but any further accesses to any other active files result in errors
166 even if the filesystem is later remounted.
170 option requires the SUIDDIR option to have been compiled into the kernel
176 pages for more information.
182 function will fail when one of the following occurs:
185 The caller is neither the super-user nor the owner of
189 belongs to a filesystem that does not support stacked mounts.
190 .It Bq Er ENAMETOOLONG
191 A component of a pathname exceeded 255 characters,
192 or the entire length of a path name exceeded 1023 characters.
194 Too many symbolic links were encountered in translating a pathname.
207 Another process currently holds a reference to
211 points outside the process's allocated address space.
214 The following errors can occur for a
219 A component of ufs_args
224 is not a block device.
226 The major device number of
228 is out of range (this indicates no device driver exists
229 for the associated hardware).
234 No space remains in the mount table.
236 The super block for the filesystem had a bad magic
237 number or an out of range block size.
239 Not enough memory was available to read the cylinder
240 group information for the filesystem.
242 An I/O error occurred while reading the super block or
243 cylinder group information.
246 points outside the process's allocated address space.
249 The following errors can occur for a
255 timed out trying to contact the server.
257 Some part of the information described by nfs_args
258 points outside the process's allocated address space.
261 The following errors can occur for a
266 No space remains in the mount table.
268 The super block for the filesystem had a bad magic
269 number or an out of range block size.
271 Not enough memory was available to read the cylinder
272 group information for the filesystem.
274 A paging error occurred while reading the super block or
275 cylinder group information.
278 points outside the process's allocated address space.
283 function may fail with one of the following errors:
286 The caller is neither the super-user nor the user who issued the corresponding
290 A component of the path is not a directory.
291 .It Bq Er ENAMETOOLONG
292 A component of a pathname exceeded 255 characters,
293 or an entire path name exceeded 1023 characters.
295 Too many symbolic links were encountered in translating the pathname.
297 The requested directory is not in the mount table.
299 A process is holding a reference to a file located
302 An I/O error occurred while writing cached filesystem information.
305 points outside the process's allocated address space.
312 mount can also fail if the maximum number of filesystems are currently
325 function calls appeared in
328 Some of the error codes need translation to more obvious messages.