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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 options that can be specified in this
121 section are ones related to security:
128 Export options are specified as follows:
131 .Fl maproot Li = Sy user
133 The credential of the specified user is used for remote access by root.
134 The credential includes all the groups to which the user is a member
135 on the local machine (see
137 The user may be specified by name or number.
138 The user string may be quoted, or use backslash escaping.
141 .Fl maproot Li = Sy user:group1:group2:...
143 The colon separated list is used to specify the precise credential
144 to be used for remote access by root.
145 The elements of the list may be either names or numbers.
146 Note that user: should be used to distinguish a credential containing
147 no groups from a complete credential for that user.
148 The group names may be quoted, or use backslash escaping.
151 .Fl mapall Li = Sy user
155 .Fl mapall Li = Sy user:group1:group2:...
157 specifies a mapping for all client UIDs (including root)
158 using the same semantics as
165 in an effort to be backward compatible with older export file formats.
171 options, remote accesses by root will result in using a credential of 65534:65533.
172 All other users will be mapped to their remote credential.
176 remote access by root will be mapped to that credential instead of 65534:65533.
180 all users (including root) will be mapped to that credential in
184 .Fl sec Li = Sy flavor1:flavor2...
186 specifies a colon separated list of acceptable security flavors to be
187 used for remote access.
188 Supported security flavors are sys, krb5, krb5i and krb5p.
189 If multiple flavors are listed, they should be ordered with the most
190 preferred flavor first.
191 If this option is not present,
192 the default security flavor list of just sys is used.
196 option specifies that the file system should be exported read-only
197 (default read/write).
202 in an effort to be backward compatible with older export file formats.
205 exports strictly according to the spec (RFC 2054 and RFC 2055) can
209 However, this flag in itself allows r/w access to all files in
210 the file system, not requiring reserved ports and not remapping UIDs.
212 is only provided to conform to the spec, and should normally not be used.
221 .Fl mapall No = Sy nobody
225 Note that only one file system can be
227 exported on a server.
231 .Fl index No = Pa file
233 option can be used to specify a file whose handle will be returned if
234 a directory is looked up using the public filehandle
236 This is to mimic the behavior of URLs.
239 option is specified, a directory filehandle will be returned as usual.
242 option only makes sense in combination with the
253 export options are used to require the client to use TLS for the mount(s)
255 For NFS mounts using TLS to work,
257 must be running on the server.
258 .Bd -filled -offset indent
260 requires that the client use TLS.
263 requires that the client use TLS and provide a verifiable X.509 certificate
264 during TLS handshake.
267 requires that the client use TLS and provide a verifiable X.509 certificate.
268 The otherName component of the certificate's subjAltName must have a
269 an OID of 1.3.6.1.4.1.2238.1.1.1 and a UTF8 string of the form
272 will be translated to the credentials of the specified user in the same
277 is normally a username is the server's password database and
279 is the DNS domain name for the server.
280 All RPCs will be performed using these credentials instead of the
281 ones in the RPC header in a manner similar to
283 .Fl mapall Li = Sy user .
287 If none of these three flags are specified, TLS mounts are permitted but
292 option will inhibit some of the syslog diagnostics for bad lines in
294 This can be useful to avoid annoying error messages for known possible
299 The third component of a line specifies the host set to which the line applies.
300 The set may be specified in three ways.
301 The first way is to list the host name(s) separated by white space.
304 addresses may be used in place of names.)
305 The second way is to specify a
311 The third way is to specify an Internet subnetwork using a network and
312 network mask that is defined as the set of all hosts with addresses within
314 This latter approach requires less overhead within the
315 kernel and is recommended for cases where the export line refers to a
316 large number of clients within an administrative subnet.
318 The first two cases are specified by simply listing the name(s) separated
320 All names are checked to see if they are
323 first and are assumed to be hostnames otherwise.
324 Using the full domain specification for a hostname can normally
325 circumvent the problem of a host that has the same name as a netgroup.
326 The third case is specified by the flag
328 .Fl network Li = Sy netname Op Li / Ar prefixlength
332 .Fl mask No = Sy netmask .
334 The netmask may be specified either by attaching a
338 option, or by using a separate
341 If the mask is not specified, it will default to the historical mask
342 for that network class (A, B, or C; see
344 This usage is deprecated, and will elicit a warning log message.
349 Scoped IPv6 address must carry scope identifier as documented in
359 For the third form which specifies the NFSv4 tree root, the directory path
360 specifies the location within the server's file system tree which is the
361 root of the NFSv4 tree.
362 There can only be one NFSv4 root directory per server.
363 As such, all entries of this form must specify the same directory path.
364 For file systems other than ZFS,
365 this location can be any directory and does not
366 need to be within an exported file system.
367 If it is not in an exported file system, a very limited set of operations
368 are permitted, so that an NFSv4 client can traverse the tree to an
369 exported file system.
370 Although parts of the NFSv4 tree can be non-exported, the entire NFSv4 tree
371 must consist of local file systems capable of being exported via NFS.
372 All ZFS file systems in the subtree below the NFSv4 tree root must be
374 NFSv4 does not use the mount protocol and does permit clients to cross server
375 mount point boundaries, although not all clients are capable of crossing the
380 option on these line(s) specifies what security flavors may be used for
381 NFSv4 operations that do not use file handles.
382 Since these operations (SetClientID, SetClientIDConfirm, Renew, DelegPurge
383 and ReleaseLockOnwer) allocate/modify state in the server, it is possible
384 to restrict some clients to the use of the krb5[ip] security flavors,
389 This third form is meaningless for NFSv2 and NFSv3 and is ignored for them.
393 utility can be made to re-read the
395 file by sending it a hangup signal as follows:
396 .Bd -literal -offset indent
397 /etc/rc.d/mountd reload
404 output to see whether
406 logged any parsing errors in the
410 .Bl -tag -width /etc/exports -compact
412 the default remote mount-point file
420 local file system mount points, let's consider the following example:
422 .Bd -literal -offset indent
423 /usr /usr/local -maproot=0:10 friends
424 /usr -maproot=daemon grumpy.cis.uoguelph.ca 131.104.48.16
425 /usr -ro -mapall=nobody
426 /u -maproot=bin: -network 131.104.48 -mask 255.255.255.0
427 /a -network 192.168.0/24
428 /a -network 3ffe:1ce1:1:fe80::/64
429 /u2 -maproot=root friends
430 /u2 -alldirs -network cis-net -mask cis-mask
431 /cdrom -alldirs,quiet,ro -network 192.168.33.0 -mask 255.255.255.0
434 V4: / -sec=krb5:krb5i:krb5p -network 131.104.48 -mask 255.255.255.0
435 V4: / -sec=sys:krb5:krb5i:krb5p grumpy.cis.uoguelph.ca
438 The file systems rooted at
442 are exported to hosts within the
445 with users mapped to their remote credentials and
446 root mapped to UID 0 and group 10.
447 They are exported read-write and the hosts in
450 The file system rooted at
455 .Em grumpy.cis.uoguelph.ca
456 with users mapped to their remote credentials and
457 root mapped to the user and groups associated with
459 it is exported to the rest of the world as read-only with
460 all users mapped to the user and groups associated with
463 The file system rooted at
465 is exported to all hosts on the subnetwork
467 with root mapped to the UID for
469 and with no group access.
471 The file system rooted at
473 is exported to the hosts in
475 with root mapped to UID and groups
478 it is exported to all hosts on network
480 allowing mounts at any
481 directory within /u2.
483 The file system rooted at
485 is exported to the network 192.168.0.0, with a netmask of 255.255.255.0.
486 However, the netmask length in the entry for
488 is not specified through a
490 option, but through the
494 The file system rooted at
496 is also exported to the IPv6 network
497 .Li 3ffe:1ce1:1:fe80::
498 address, using the upper 64 bits as the prefix.
499 Note that, unlike with IPv4 network addresses, the specified network
500 address must be complete, and not just contain the upper bits.
501 With IPv6 addresses, the
503 option must not be used.
505 The file system rooted at
507 will be exported read-only to the entire network 192.168.33.0/24, including
508 all its subdirectories.
511 is the conventional mountpoint for a CD-ROM device, this export will
512 fail if no CD-ROM medium is currently mounted there since that line
513 would then attempt to export a subdirectory of the root file system
516 option which is not allowed.
519 option will then suppress the error message for this condition that
520 would normally be syslogged.
521 As soon as an actual CD-ROM is going to be mounted,
525 about this situation, and the
527 file system will be exported as intended.
528 Note that without using the
530 option, the export would always succeed.
531 While there is no CD-ROM medium mounted under
533 it would export the (normally empty) directory
535 of the root file system instead.
537 The file system rooted at
539 will be exported using Kerberos 5 authentication and will require
540 integrity protected messages for all accesses.
541 The file system rooted at
543 will also be exported using Kerberos 5 authentication and all messages
544 used to access it will be encrypted.
546 For the experimental server, the NFSv4 tree is rooted at ``/'',
547 and any client within the 131.104.48 subnet is permitted to perform NFSv4 state
548 operations on the server, so long as valid Kerberos credentials are provided.
549 The machine grumpy.cis.uoguelph.ca is permitted to perform NFSv4 state
550 operations on the server using AUTH_SYS credentials, as well as Kerberos ones.
552 In the following example some directories are exported as NFSv3 and NFSv4:
553 .Bd -literal -offset indent
555 /wingsdl/nfsv4/usr-ports -maproot=root -network 172.16.0.0 -mask 255.255.0.0
556 /wingsdl/nfsv4/clasper -maproot=root clasper
559 Only one V4: line is needed or allowed to declare where NFSv4 is
561 The other lines declare specific exported directories with
562 their absolute paths given in /etc/exports.
564 The exported directories' paths are used for both v3 and v4.
565 However, they are interpreted differently for v3 and v4.
566 A client mount command for usr-ports would use the server-absolute name when
568 .Bd -literal -offset indent
569 mount server:/wingsdl/nfsv4/usr-ports /mnt/tmp
572 A mount command using NFSv4 would use the path relative to the NFSv4
574 .Bd -literal -offset indent
575 mount server:/usr-ports /mnt/tmp
578 This also differentiates which version you want if the client can do
580 The former will only ever do a v3 mount and the latter will only ever
583 Note that due to different mount behavior between NFSv3 and NFSv4 a
584 NFSv4 mount request for a directory that the client does not have
585 permission for will succeed and read/write access will fail
586 afterwards, whereas NFSv3 rejects the mount request.
595 The implementation is based on the following documents:
599 .%T "Network File System Protocol Specification, Appendix A, RFC 1094"
603 .%T "NFS: Network File System Version 3, Appendix I, RFC 1813"
607 .%T "Towards Remote Procedure Call Encryption By Default, RFC nnnn"
611 The export options are tied to the local mount points in the kernel and
612 must be non-contradictory for any exported subdirectory of the local
614 It is recommended that all exported directories within the same server
615 file system be specified on adjacent lines going down the tree.
616 You cannot specify a hostname that is also the name of a netgroup.
617 Specifying the full domain specification for a hostname can normally
618 circumvent the problem.