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33 .Nd define remote mount points for
41 file specifies remote mount points for the
43 mount protocol per the
45 server specification; see
46 .%T "Network File System Protocol Specification" ,
47 RFC1094, Appendix A and
48 .%T "NFS: Network File System Version 3 Specification" ,
52 (other than comment lines that begin with a #)
53 specifies the mount point(s) and export flags within one local server
54 file system or the NFSv4 tree root for one or more hosts.
55 A long line may be split over several lines by ending all but the
56 last line with a backslash
58 A host may be specified only once for each local file or the NFSv4 tree root on the
59 server and there may be only one default entry for each server
60 file system that applies to all other hosts.
61 The latter exports the file system to the
64 be used only when the file system contains public information.
67 the first field(s) specify the directory path(s) within a server file system
68 that can be mounted on by the corresponding client(s).
69 There are three 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 file system
83 this form allows the host(s) to mount at any point within the file system,
84 including regular files if the
88 Because NFSv4 does not use the mount protocol,
90 .Dq administrative controls
91 are not applied and all directories within this server
92 file system are mountable via NFSv4 even if the
94 flag has not been specified.
95 The third form has the string ``V4:'' followed by a single absolute path
96 name, to specify the NFSv4 tree root.
97 This line does not export any file system, but simply marks where the root
98 of the server's directory tree is for NFSv4 clients.
99 The exported file systems for NFSv4 are specified via the other lines
102 file in the same way as for NFSv2 and NFSv3.
103 The pathnames must not have any symbolic links in them and should not have
109 Mount points for a file system may appear on multiple lines each with
110 different sets of hosts and export options.
112 The second component of a line specifies how the file system is to be
113 exported to the host set.
114 The option flags specify whether the file system
115 is exported read-only or read-write and how the client UID is mapped to
116 user credentials on the server.
117 For the NFSv4 tree root, the only options that can be specified in this
118 section are ones related to security:
125 Export options are specified as follows:
128 .Fl maproot Li = Sy user
130 The credential of the specified user is used for remote access by root.
131 The credential includes all the groups to which the user is a member
132 on the local machine (see
134 The user may be specified by name or number.
135 The user string may be quoted, or use backslash escaping.
138 .Fl maproot Li = Sy user:group1:group2:...
140 The colon separated list is used to specify the precise credential
141 to be used for remote access by root.
142 The elements of the list may be either names or numbers.
143 Note that user: should be used to distinguish a credential containing
144 no groups from a complete credential for that user.
145 The group names may be quoted, or use backslash escaping.
148 .Fl mapall Li = Sy user
152 .Fl mapall Li = Sy user:group1:group2:...
154 specifies a mapping for all client UIDs (including root)
155 using the same semantics as
162 in an effort to be backward compatible with older export file formats.
168 options, remote accesses by root will result in using a credential of 65534:65533.
169 All other users will be mapped to their remote credential.
173 remote access by root will be mapped to that credential instead of 65534:65533.
177 all users (including root) will be mapped to that credential in
181 .Fl sec Li = Sy flavor1:flavor2...
183 specifies a colon separated list of acceptable security flavors to be
184 used for remote access.
185 Supported security flavors are sys, krb5, krb5i and krb5p.
186 If multiple flavors are listed, they should be ordered with the most
187 preferred flavor first.
188 If this option is not present,
189 the default security flavor list of just sys is used.
193 option specifies that the file system should be exported read-only
194 (default read/write).
199 in an effort to be backward compatible with older export file formats.
202 exports strictly according to the spec (RFC 2054 and RFC 2055) can
206 However, this flag in itself allows r/w access to all files in
207 the file system, not requiring reserved ports and not remapping UIDs.
209 is only provided to conform to the spec, and should normally not be used.
218 .Fl mapall No = Sy nobody
222 Note that only one file system can be
224 exported on a server.
228 .Fl index No = Pa file
230 option can be used to specify a file whose handle will be returned if
231 a directory is looked up using the public filehandle
233 This is to mimic the behavior of URLs.
236 option is specified, a directory filehandle will be returned as usual.
239 option only makes sense in combination with the
250 export options are used to require the client to use TLS for the mount(s)
252 For NFS mounts using TLS to work,
254 must be running on the server.
255 .Bd -filled -offset indent
257 requires that the client use TLS.
260 requires that the client use TLS and provide a verifiable X.509 certificate
261 during TLS handshake.
264 requires that the client use TLS and provide a verifiable X.509 certificate.
265 The otherName component of the certificate's subjAltName must have a
266 an OID of 1.3.6.1.4.1.2238.1.1.1 and a UTF8 string of the form
269 will be translated to the credentials of the specified user in the same
274 is normally a username is the server's password database and
276 is the DNS domain name for the server.
277 All RPCs will be performed using these credentials instead of the
278 ones in the RPC header in a manner similar to
280 .Fl mapall Li = Sy user .
284 If none of these three flags are specified, TLS mounts are permitted but
289 option will inhibit some of the syslog diagnostics for bad lines in
291 This can be useful to avoid annoying error messages for known possible
296 The third component of a line specifies the host set to which the line applies.
297 The set may be specified in three ways.
298 The first way is to list the host name(s) separated by white space.
301 addresses may be used in place of names.)
302 The second way is to specify a
308 The third way is to specify an Internet subnetwork using a network and
309 network mask that is defined as the set of all hosts with addresses within
311 This latter approach requires less overhead within the
312 kernel and is recommended for cases where the export line refers to a
313 large number of clients within an administrative subnet.
315 The first two cases are specified by simply listing the name(s) separated
317 All names are checked to see if they are
320 first and are assumed to be hostnames otherwise.
321 Using the full domain specification for a hostname can normally
322 circumvent the problem of a host that has the same name as a netgroup.
323 The third case is specified by the flag
325 .Fl network Li = Sy netname Op Li / Ar prefixlength
329 .Fl mask No = Sy netmask .
331 The netmask may be specified either by attaching a
335 option, or by using a separate
338 If the mask is not specified, it will default to the historical mask
339 for that network class (A, B, or C; see
341 This usage is deprecated, and will elicit a warning log message.
346 Scoped IPv6 address must carry scope identifier as documented in
356 For the third form which specifies the NFSv4 tree root, the directory path
357 specifies the location within the server's file system tree which is the
358 root of the NFSv4 tree.
359 There can only be one NFSv4 root directory per server.
360 As such, all entries of this form must specify the same directory path.
361 For file systems other than ZFS,
362 this location can be any directory and does not
363 need to be within an exported file system.
364 If it is not in an exported file system, a very limited set of operations
365 are permitted, so that an NFSv4 client can traverse the tree to an
366 exported file system.
367 Although parts of the NFSv4 tree can be non-exported, the entire NFSv4 tree
368 must consist of local file systems capable of being exported via NFS.
369 All ZFS file systems in the subtree below the NFSv4 tree root must be
371 NFSv4 does not use the mount protocol and does permit clients to cross server
372 mount point boundaries, although not all clients are capable of crossing the
377 option on these line(s) specifies what security flavors may be used for
378 NFSv4 operations that do not use file handles.
379 Since these operations (SetClientID, SetClientIDConfirm, Renew, DelegPurge
380 and ReleaseLockOnwer) allocate/modify state in the server, it is possible
381 to restrict some clients to the use of the krb5[ip] security flavors,
386 This third form is meaningless for NFSv2 and NFSv3 and is ignored for them.
390 utility can be made to re-read the
392 file by sending it a hangup signal as follows:
393 .Bd -literal -offset indent
394 /etc/rc.d/mountd reload
401 output to see whether
403 logged any parsing errors in the
407 .Bl -tag -width /etc/exports -compact
409 the default remote mount-point file
417 local file system mount points, let's consider the following example:
419 .Bd -literal -offset indent
420 /usr /usr/local -maproot=0:10 friends
421 /usr -maproot=daemon grumpy.cis.uoguelph.ca 131.104.48.16
422 /usr -ro -mapall=nobody
423 /u -maproot=bin: -network 131.104.48 -mask 255.255.255.0
424 /a -network 192.168.0/24
425 /a -network 3ffe:1ce1:1:fe80::/64
426 /u2 -maproot=root friends
427 /u2 -alldirs -network cis-net -mask cis-mask
428 /cdrom -alldirs,quiet,ro -network 192.168.33.0 -mask 255.255.255.0
431 V4: / -sec=krb5:krb5i:krb5p -network 131.104.48 -mask 255.255.255.0
432 V4: / -sec=sys:krb5:krb5i:krb5p grumpy.cis.uoguelph.ca
435 The file systems rooted at
439 are exported to hosts within the
442 with users mapped to their remote credentials and
443 root mapped to UID 0 and group 10.
444 They are exported read-write and the hosts in
447 The file system rooted at
452 .Em grumpy.cis.uoguelph.ca
453 with users mapped to their remote credentials and
454 root mapped to the user and groups associated with
456 it is exported to the rest of the world as read-only with
457 all users mapped to the user and groups associated with
460 The file system rooted at
462 is exported to all hosts on the subnetwork
464 with root mapped to the UID for
466 and with no group access.
468 The file system rooted at
470 is exported to the hosts in
472 with root mapped to UID and groups
475 it is exported to all hosts on network
477 allowing mounts at any
478 directory within /u2.
480 The file system rooted at
482 is exported to the network 192.168.0.0, with a netmask of 255.255.255.0.
483 However, the netmask length in the entry for
485 is not specified through a
487 option, but through the
491 The file system rooted at
493 is also exported to the IPv6 network
494 .Li 3ffe:1ce1:1:fe80::
495 address, using the upper 64 bits as the prefix.
496 Note that, unlike with IPv4 network addresses, the specified network
497 address must be complete, and not just contain the upper bits.
498 With IPv6 addresses, the
500 option must not be used.
502 The file system rooted at
504 will be exported read-only to the entire network 192.168.33.0/24, including
505 all its subdirectories.
508 is the conventional mountpoint for a CD-ROM device, this export will
509 fail if no CD-ROM medium is currently mounted there since that line
510 would then attempt to export a subdirectory of the root file system
513 option which is not allowed.
516 option will then suppress the error message for this condition that
517 would normally be syslogged.
518 As soon as an actual CD-ROM is going to be mounted,
522 about this situation, and the
524 file system will be exported as intended.
525 Note that without using the
527 option, the export would always succeed.
528 While there is no CD-ROM medium mounted under
530 it would export the (normally empty) directory
532 of the root file system instead.
534 The file system rooted at
536 will be exported using Kerberos 5 authentication and will require
537 integrity protected messages for all accesses.
538 The file system rooted at
540 will also be exported using Kerberos 5 authentication and all messages
541 used to access it will be encrypted.
543 For the experimental server, the NFSv4 tree is rooted at ``/'',
544 and any client within the 131.104.48 subnet is permitted to perform NFSv4 state
545 operations on the server, so long as valid Kerberos credentials are provided.
546 The machine grumpy.cis.uoguelph.ca is permitted to perform NFSv4 state
547 operations on the server using AUTH_SYS credentials, as well as Kerberos ones.
549 In the following example some directories are exported as NFSv3 and NFSv4:
550 .Bd -literal -offset indent
552 /wingsdl/nfsv4/usr-ports -maproot=root -network 172.16.0.0 -mask 255.255.0.0
553 /wingsdl/nfsv4/clasper -maproot=root clasper
556 Only one V4: line is needed or allowed to declare where NFSv4 is
558 The other lines declare specific exported directories with
559 their absolute paths given in /etc/exports.
561 The exported directories' paths are used for both v3 and v4.
562 However, they are interpreted differently for v3 and v4.
563 A client mount command for usr-ports would use the server-absolute name when
565 .Bd -literal -offset indent
566 mount server:/wingsdl/nfsv4/usr-ports /mnt/tmp
569 A mount command using NFSv4 would use the path relative to the NFSv4
571 .Bd -literal -offset indent
572 mount server:/usr-ports /mnt/tmp
575 This also differentiates which version you want if the client can do
577 The former will only ever do a v3 mount and the latter will only ever
580 Note that due to different mount behavior between NFSv3 and NFSv4 a
581 NFSv4 mount request for a directory that the client does not have
582 permission for will succeed and read/write access will fail
583 afterwards, whereas NFSv3 rejects the mount request.
592 The implementation is based on the following documents:
596 .%T "Network File System Protocol Specification, Appendix A, RFC 1094"
600 .%T "NFS: Network File System Version 3, Appendix I, RFC 1813"
604 .%T "Towards Remote Procedure Call Encryption By Default, RFC nnnn"
608 The export options are tied to the local mount points in the kernel and
609 must be non-contradictory for any exported subdirectory of the local
611 It is recommended that all exported directories within the same server
612 file system be specified on adjacent lines going down the tree.
613 You cannot specify a hostname that is also the name of a netgroup.
614 Specifying the full domain specification for a hostname can normally
615 circumvent the problem.