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28 .\" @(#)exports.5 8.3 (Berkeley) 3/29/95
29 .\" $FreeBSD: src/sbin/mountd/exports.5,v 1.10.2.8 2002/09/28 16:31:45 markm Exp $
30 .\" $DragonFly: src/sbin/mountd/exports.5,v 1.5 2007/11/23 23:16:36 swildner Exp $
37 .Nd define remote mount points for
45 file specifies remote mount points for the
47 mount protocol per the
49 server specification; see
50 .%T "Network File System Protocol Specification" ,
51 RFC 1094, Appendix A and
52 .%T "NFS: Network File System Version 3 Specification" ,
56 (other than comment lines that begin with a #)
57 specifies the mount point(s) and export flags within one local server
58 filesystem for one or more hosts.
59 A host may be specified only once for each local filesystem on the
60 server and there may be only one default entry for each server
61 filesystem that applies to all other hosts.
62 The latter exports the filesystem to the
64 and should be used only when the filesystem contains public information.
67 the first field(s) specify the directory path(s) within a server filesystem
68 that can be mounted on by the corresponding client(s).
69 There are two forms of this specification.
70 The first is to list all mount points as absolute
71 directory paths separated by whitespace.
72 This list of directory paths should be considered an
73 .Dq administrative control ,
74 since it is only enforced by the
76 daemon and not the kernel.
77 As such, it only applies to NFSv2 and NFSv3 mounts and only
78 with respect to the client's use of the mount protocol.
79 The second is to specify the pathname of the root of the filesystem
83 this form allows the host(s) to mount at any point within the filesystem,
84 including regular files if the
88 The pathnames must not have any symbolic links in them and should not have
94 Mount points for a filesystem may appear on multiple lines each with
95 different sets of hosts and export options.
97 The second component of a line specifies how the filesystem is to be
98 exported to the host set.
99 The option flags specify whether the filesystem
100 is exported read-only or read-write and how the client UID is mapped to
101 user credentials on the server.
103 Export options are specified as follows:
106 .Fl maproot Li = Sy user
108 The credential of the specified user is used for remote access by root.
109 The credential includes all the groups to which the user is a member
110 on the local machine (see
112 The user may be specified by name or number.
115 .Fl maproot Li = Sy user:group1:group2:...
117 The colon separated list is used to specify the precise credential
118 to be used for remote access by root.
119 The elements of the list may be either names or numbers.
120 Note that user: should be used to distinguish a credential containing
121 no groups from a complete credential for that user.
124 .Fl mapall Li = Sy user
128 .Fl mapall Li = Sy user:group1:group2:...
130 specifies a mapping for all client UIDs (including root)
131 using the same semantics as
138 in an effort to be backward compatible with older export file formats.
144 options, remote accesses by root will result in using a credential of 65534:65533.
145 All other users will be mapped to their remote credential.
149 remote access by root will be mapped to that credential instead of 65534:65533.
153 all users (including root) will be mapped to that credential in
158 option specifies that the filesystem should be exported read-only
159 (default read/write).
164 in an effort to be backward compatible with older export file formats.
167 exports strictly according to the spec (RFC 2054 and RFC 2055) can
171 However, this flag in itself allows r/w access to all files in
172 the file system, not requiring reserved ports and not remapping UIDs.
174 is only provided to conform to the spec, and should normally not be used.
183 .Fl mapall No = Sy nobody
190 .Fl index No = Sy file
192 option can be used to specify a file whose handle will be returned if
193 a directory is looked up using the public filehandle
195 This is to mimic the behavior of URLs.
198 option is specified, a directory filehandle will be returned as usual.
201 option only makes sense in combination with the
209 option will inhibit some of the syslog diagnostics for bad lines in
211 This can be useful to avoid annoying error messages for known possible
216 The third component of a line specifies the host set to which the line applies.
217 The set may be specified in three ways.
218 The first way is to list the host name(s) separated by white space.
221 addresses may be used in place of names.)
222 The second way is to specify a
228 The third way is to specify an Internet subnetwork using a network and
229 network mask that is defined as the set of all hosts with addresses within
231 This latter approach requires less overhead within the
232 kernel and is recommended for cases where the export line refers to a
233 large number of clients within an administrative subnet.
235 The first two cases are specified by simply listing the name(s) separated
237 All names are checked to see if they are
239 names first and are assumed to be hostnames otherwise.
240 Using the full domain specification for a hostname can normally
241 circumvent the problem of a host that has the same name as a netgroup.
242 The third case is specified by the flag
244 .Fl network Li = Sy netname Op Li / Ar prefixlength
248 .Fl mask No = Sy netmask .
250 The netmask may be specified either by attaching a
254 option, or by using a separate
257 If the mask is not specified, it will default to the mask for that network
258 class (A, B or C; see
266 utility can be made to re-read the
268 file by sending it a hangup signal as follows:
269 .Bd -literal -offset indent
270 /etc/rc.d/mountd reload
277 output to see whether
279 logged any parsing errors in the
283 .Bl -tag -width /etc/exports -compact
285 the default remote mount-point file
288 .Bd -literal -offset indent
289 /usr /usr/local -maproot=0:10 friends
290 /usr -maproot=daemon grumpy.cis.uoguelph.ca 131.104.48.16
291 /usr -ro -mapall=nobody
292 /u -maproot=bin: -network 131.104.48 -mask 255.255.255.0
293 /a -network 192.168.0/24
294 /u2 -maproot=root friends
295 /u2 -alldirs -network cis-net -mask cis-mask
296 /cdrom -alldirs,quiet,ro -network 192.168.33.0 -mask 255.255.255.0
306 local filesystem mount points, the above example specifies the following:
308 The file system rooted at
312 where friends is specified in the netgroup file
313 with users mapped to their remote credentials and
314 root mapped to UID 0 and group 10.
315 It is exported read-write and the hosts in
324 .Em grumpy.cis.uoguelph.ca
325 with users mapped to their remote credentials and
326 root mapped to the user and groups associated with
328 it is exported to the rest of the world as read-only with
329 all users mapped to the user and groups associated with
332 The file system rooted at
334 is exported to all hosts on the subnetwork
336 with root mapped to the UID for
338 and with no group access.
340 The file system rooted at
342 is exported to the hosts in
344 with root mapped to UID and groups
347 it is exported to all hosts on network
349 allowing mounts at any
350 directory within /u2.
352 The file system rooted at
354 is exported to the network 192.168.0.0, with a netmask of 255.255.255.0.
355 However, the netmask length in the entry for
357 is not specified through a
359 option, but through the
363 The filesystem rooted at
365 will exported read-only to the entire network 192.168.33.0/24, including
366 all its subdirectories.
369 is the conventional mountpoint for a CD-ROM device, this export will
370 fail if no CD-ROM medium is currently mounted there since that line
371 would then attempt to export a subdirectory of the root filesystem
374 option which is not allowed.
377 option will then suppress the error message for this condition that
378 would normally be syslogged.
379 As soon as an actual CD-ROM is going to be mounted,
383 about this situation, and the
385 filesystem will be exported as intended.
386 Note that without using the
388 option, the export would always succeed.
389 While there is no CD-ROM medium mounted under
391 it would export the (normally empty) directory
393 of the root filesystem instead.
400 The export options are tied to the local mount points in the kernel and
401 must be non-contradictory for any exported subdirectory of the local
403 It is recommended that all exported directories within the same server
404 filesystem be specified on adjacent lines going down the tree.
405 You cannot specify a hostname that is also the name of a netgroup.
406 Specifying the full domain specification for a hostname can normally
407 circumvent the problem.