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28 .\" @(#)exports.5 8.3 (Berkeley) 3/29/95
36 .Nd define remote mount points for
44 file specifies remote mount points for the
46 mount protocol per the
48 server specification; see
49 .%T "Network File System Protocol Specification" ,
50 RFC1094, Appendix A and
51 .%T "NFS: Network File System Version 3 Specification" ,
55 (other than comment lines that begin with a #)
56 specifies the mount point(s) and export flags within one local server
57 file system or the NFSv4 tree root for one or more hosts.
58 A long line may be split over several lines by ending all but the
59 last line with a backslash
61 A host may be specified only once for each local file or the NFSv4 tree root on the
62 server and there may be only one default entry for each server
63 file system that applies to all other hosts.
64 The latter exports the file system to the
67 be used only when the file system contains public information.
70 the first field(s) specify the directory path(s) within a server file system
71 that can be mounted on by the corresponding client(s).
72 There are three forms of this specification.
73 The first is to list all mount points as absolute
74 directory paths separated by whitespace.
75 This list of directory paths should be considered an
76 .Dq administrative control ,
77 since it is only enforced by the
79 daemon and not the kernel.
80 As such, it only applies to NFSv2 and NFSv3 mounts and only
81 with respect to the client's use of the mount protocol.
82 The second is to specify the pathname of the root of the file system
86 this form allows the host(s) to mount at any point within the file system,
87 including regular files if the
91 Because NFSv4 does not use the mount protocol,
93 .Dq administrative controls
94 are not applied and all directories within this server
95 file system are mountable via NFSv4 even if the
97 flag has not been specified.
98 The third form has the string ``V4:'' followed by a single absolute path
99 name, to specify the NFSv4 tree root.
100 This line does not export any file system, but simply marks where the root
101 of the server's directory tree is for NFSv4 clients.
102 The exported file systems for NFSv4 are specified via the other lines
105 file in the same way as for NFSv2 and NFSv3.
106 The pathnames must not have any symbolic links in them and should not have
112 Mount points for a file system may appear on multiple lines each with
113 different sets of hosts and export options.
115 The second component of a line specifies how the file system is to be
116 exported to the host set.
117 The option flags specify whether the file system
118 is exported read-only or read-write and how the client UID is mapped to
119 user credentials on the server.
120 For the NFSv4 tree root, the only option that can be specified in this
124 Export options are specified as follows:
127 .Fl maproot Li = Sy user
129 The credential of the specified user is used for remote access by root.
130 The credential includes all the groups to which the user is a member
131 on the local machine (see
133 The user may be specified by name or number.
134 The user string may be quoted, or use backslash escaping.
137 .Fl maproot Li = Sy user:group1:group2:...
139 The colon separated list is used to specify the precise credential
140 to be used for remote access by root.
141 The elements of the list may be either names or numbers.
142 Note that user: should be used to distinguish a credential containing
143 no groups from a complete credential for that user.
144 The group names may be quoted, or use backslash escaping.
147 .Fl mapall Li = Sy user
151 .Fl mapall Li = Sy user:group1:group2:...
153 specifies a mapping for all client UIDs (including root)
154 using the same semantics as
161 in an effort to be backward compatible with older export file formats.
167 options, remote accesses by root will result in using a credential of 65534:65533.
168 All other users will be mapped to their remote credential.
172 remote access by root will be mapped to that credential instead of 65534:65533.
176 all users (including root) will be mapped to that credential in
180 .Fl sec Li = Sy flavor1:flavor2...
182 specifies a colon separated list of acceptable security flavors to be
183 used for remote access.
184 Supported security flavors are sys, krb5, krb5i and krb5p.
185 If multiple flavors are listed, they should be ordered with the most
186 preferred flavor first.
187 If this option is not present,
188 the default security flavor list of just sys is used.
192 option specifies that the file system should be exported read-only
193 (default read/write).
198 in an effort to be backward compatible with older export file formats.
201 exports strictly according to the spec (RFC 2054 and RFC 2055) can
205 However, this flag in itself allows r/w access to all files in
206 the file system, not requiring reserved ports and not remapping UIDs.
208 is only provided to conform to the spec, and should normally not be used.
217 .Fl mapall No = Sy nobody
221 Note that only one file system can be
223 exported on a server.
227 .Fl index No = Pa file
229 option can be used to specify a file whose handle will be returned if
230 a directory is looked up using the public filehandle
232 This is to mimic the behavior of URLs.
235 option is specified, a directory filehandle will be returned as usual.
238 option only makes sense in combination with the
246 option will inhibit some of the syslog diagnostics for bad lines in
248 This can be useful to avoid annoying error messages for known possible
253 The third component of a line specifies the host set to which the line applies.
254 The set may be specified in three ways.
255 The first way is to list the host name(s) separated by white space.
258 addresses may be used in place of names.)
259 The second way is to specify a
265 The third way is to specify an Internet subnetwork using a network and
266 network mask that is defined as the set of all hosts with addresses within
268 This latter approach requires less overhead within the
269 kernel and is recommended for cases where the export line refers to a
270 large number of clients within an administrative subnet.
272 The first two cases are specified by simply listing the name(s) separated
274 All names are checked to see if they are
277 first and are assumed to be hostnames otherwise.
278 Using the full domain specification for a hostname can normally
279 circumvent the problem of a host that has the same name as a netgroup.
280 The third case is specified by the flag
282 .Fl network Li = Sy netname Op Li / Ar prefixlength
286 .Fl mask No = Sy netmask .
288 The netmask may be specified either by attaching a
292 option, or by using a separate
295 If the mask is not specified, it will default to the mask for that network
296 class (A, B or C; see
302 Scoped IPv6 address must carry scope identifier as documented in
312 For the third form which specifies the NFSv4 tree root, the directory path
313 specifies the location within the server's file system tree which is the
314 root of the NFSv4 tree.
315 There can only be one NFSv4 root directory per server.
316 As such, all entries of this form must specify the same directory path.
317 For file systems other than ZFS,
318 this location can be any directory and does not
319 need to be within an exported file system. If it is not in an exported
320 file system, a very limited set of operations are permitted, so that an
321 NFSv4 client can traverse the tree to an exported file system.
322 Although parts of the NFSv4 tree can be non-exported, the entire NFSv4 tree
323 must consist of local file systems capable of being exported via NFS.
324 All ZFS file systems in the subtree below the NFSv4 tree root must be
326 NFSv4 does not use the mount protocol and does permit clients to cross server
327 mount point boundaries, although not all clients are capable of crossing the
332 option on these line(s) specifies what security flavors may be used for
333 NFSv4 operations that do not use file handles. Since these operations
334 (SetClientID, SetClientIDConfirm, Renew, DelegPurge and ReleaseLockOnwer)
335 allocate/modify state in the server, it is possible to restrict some clients to
336 the use of the krb5[ip] security flavors, via this option.
340 This third form is meaningless for NFSv2 and NFSv3 and is ignored for them.
344 utility can be made to re-read the
346 file by sending it a hangup signal as follows:
347 .Bd -literal -offset indent
348 /etc/rc.d/mountd reload
355 output to see whether
357 logged any parsing errors in the
361 .Bl -tag -width /etc/exports -compact
363 the default remote mount-point file
366 .Bd -literal -offset indent
367 /usr /usr/local -maproot=0:10 friends
368 /usr -maproot=daemon grumpy.cis.uoguelph.ca 131.104.48.16
369 /usr -ro -mapall=nobody
370 /u -maproot=bin: -network 131.104.48 -mask 255.255.255.0
371 /a -network 192.168.0/24
372 /a -network 3ffe:1ce1:1:fe80::/64
373 /u2 -maproot=root friends
374 /u2 -alldirs -network cis-net -mask cis-mask
375 /cdrom -alldirs,quiet,ro -network 192.168.33.0 -mask 255.255.255.0
378 V4: / -sec=krb5:krb5i:krb5p -network 131.104.48 -mask 255.255.255.0
379 V4: / -sec=sys:krb5:krb5i:krb5p grumpy.cis.uoguelph.ca
387 local file system mount points, the above example specifies the following:
389 The file system rooted at
393 where friends is specified in the netgroup file
394 with users mapped to their remote credentials and
395 root mapped to UID 0 and group 10.
396 It is exported read-write and the hosts in
405 .Em grumpy.cis.uoguelph.ca
406 with users mapped to their remote credentials and
407 root mapped to the user and groups associated with
409 it is exported to the rest of the world as read-only with
410 all users mapped to the user and groups associated with
413 The file system rooted at
415 is exported to all hosts on the subnetwork
417 with root mapped to the UID for
419 and with no group access.
421 The file system rooted at
423 is exported to the hosts in
425 with root mapped to UID and groups
428 it is exported to all hosts on network
430 allowing mounts at any
431 directory within /u2.
433 The file system rooted at
435 is exported to the network 192.168.0.0, with a netmask of 255.255.255.0.
436 However, the netmask length in the entry for
438 is not specified through a
440 option, but through the
444 The file system rooted at
446 is also exported to the IPv6 network
447 .Li 3ffe:1ce1:1:fe80::
448 address, using the upper 64 bits as the prefix.
449 Note that, unlike with IPv4 network addresses, the specified network
450 address must be complete, and not just contain the upper bits.
451 With IPv6 addresses, the
453 option must not be used.
455 The file system rooted at
457 will be exported read-only to the entire network 192.168.33.0/24, including
458 all its subdirectories.
461 is the conventional mountpoint for a CD-ROM device, this export will
462 fail if no CD-ROM medium is currently mounted there since that line
463 would then attempt to export a subdirectory of the root file system
466 option which is not allowed.
469 option will then suppress the error message for this condition that
470 would normally be syslogged.
471 As soon as an actual CD-ROM is going to be mounted,
475 about this situation, and the
477 file system will be exported as intended.
478 Note that without using the
480 option, the export would always succeed.
481 While there is no CD-ROM medium mounted under
483 it would export the (normally empty) directory
485 of the root file system instead.
487 The file system rooted at
489 will be exported using Kerberos 5 authentication and will require
490 integrity protected messages for all accesses.
491 The file system rooted at
493 will also be exported using Kerberos 5 authentication and all messages
494 used to access it will be encrypted.
496 For the experimental server, the NFSv4 tree is rooted at ``/'',
497 and any client within the 131.104.48 subnet is permitted to perform NFSv4 state
498 operations on the server, so long as valid Kerberos credentials are provided.
499 The machine grumpy.cis.uoguelph.ca is permitted to perform NFSv4 state
500 operations on the server using AUTH_SYS credentials, as well as Kerberos ones.
502 In the following example some directories are exported as NFSv3 and NFSv4:
503 .Bd -literal -offset indent
505 /wingsdl/nfsv4/usr-ports -maproot=root -network 172.16.0.0 -mask 255.255.0.0
506 /wingsdl/nfsv4/clasper -maproot=root clasper
509 Only one V4: line is needed or allowed to declare where NFSv4 is
510 rooted. The other lines declare specific exported directories with
511 their absolute paths given in /etc/exports.
513 The exported directories' paths are used for both v3 and v4.
514 However, they are interpreted differently for v3 and v4. A client
515 mount command for usr-ports would use the server-absolute name when
517 .Bd -literal -offset indent
518 mount server:/wingsdl/nfsv4/usr-ports /mnt/tmp
521 A mount command using NFSv4 would use the path relative to the NFSv4
523 .Bd -literal -offset indent
524 mount server:/usr-ports /mnt/tmp
527 This also differentiates which version you want if the client can do
528 both v3 and v4. The former will only ever do a v3 mount and the
529 latter will only ever do a v4 mount.
531 Note that due to different mount behavior between NFSv3 and NFSv4 a
532 NFSv4 mount request for a directory that the client does not have
533 permission for will succeed and read/write access will fail
534 afterwards, whereas NFSv3 rejects the mount request.
542 The export options are tied to the local mount points in the kernel and
543 must be non-contradictory for any exported subdirectory of the local
545 It is recommended that all exported directories within the same server
546 file system be specified on adjacent lines going down the tree.
547 You cannot specify a hostname that is also the name of a netgroup.
548 Specifying the full domain specification for a hostname can normally
549 circumvent the problem.