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28 .\" @(#)exports.5 8.3 (Berkeley) 3/29/95
35 .Nd define remote mount points for
43 file specifies remote mount points for the
45 mount protocol per the
47 server specification; see
48 .%T "Network File System Protocol Specification" ,
49 RFC1094, Appendix A and
50 .%T "NFS: Network File System Version 3 Specification" ,
54 (other than comment lines that begin with a #)
55 specifies the mount point(s) and export flags within one local server
56 file system or the NFSv4 tree root for one or more hosts.
57 A long line may be split over several lines by ending all but the
58 last line with a backslash
60 A host may be specified only once for each local file or the NFSv4 tree root on the
61 server and there may be only one default entry for each server
62 file system that applies to all other hosts.
63 The latter exports the file system to the
66 be used only when the file system contains public information.
69 the first field(s) specify the directory path(s) within a server file system
70 that can be mounted on by the corresponding client(s).
71 There are three forms of this specification.
72 The first is to list all mount points as absolute
73 directory paths separated by whitespace.
74 This list of directory paths should be considered an
75 .Dq administrative control ,
76 since it is only enforced by the
78 daemon and not the kernel.
79 As such, it only applies to NFSv2 and NFSv3 mounts and only
80 with respect to the client's use of the mount protocol.
81 The second is to specify the pathname of the root of the file system
85 this form allows the host(s) to mount at any point within the file system,
86 including regular files if the
90 Because NFSv4 does not use the mount protocol,
92 .Dq administrative controls
93 are not applied and all directories within this server
94 file system are mountable via NFSv4 even if the
96 flag has not been specified.
97 The third form has the string ``V4:'' followed by a single absolute path
98 name, to specify the NFSv4 tree root.
99 This line does not export any file system, but simply marks where the root
100 of the server's directory tree is for NFSv4 clients.
101 The exported file systems for NFSv4 are specified via the other lines
104 file in the same way as for NFSv2 and NFSv3.
105 The pathnames must not have any symbolic links in them and should not have
111 Mount points for a file system may appear on multiple lines each with
112 different sets of hosts and export options.
114 The second component of a line specifies how the file system is to be
115 exported to the host set.
116 The option flags specify whether the file system
117 is exported read-only or read-write and how the client UID is mapped to
118 user credentials on the server.
119 For the NFSv4 tree root, the only options that can be specified in this
120 section are ones related to security:
127 Export options are specified as follows:
130 .Fl maproot Li = Sy user
132 The credential of the specified user is used for remote access by root.
133 The credential includes all the groups to which the user is a member
134 on the local machine (see
136 The user may be specified by name or number.
137 The user string may be quoted, or use backslash escaping.
140 .Fl maproot Li = Sy user:group1:group2:...
142 The colon separated list is used to specify the precise credential
143 to be used for remote access by root.
144 The elements of the list may be either names or numbers.
145 Note that user: should be used to distinguish a credential containing
146 no groups from a complete credential for that user.
147 The group names may be quoted, or use backslash escaping.
150 .Fl mapall Li = Sy user
154 .Fl mapall Li = Sy user:group1:group2:...
156 specifies a mapping for all client UIDs (including root)
157 using the same semantics as
164 in an effort to be backward compatible with older export file formats.
170 options, remote accesses by root will result in using a credential of 65534:65533.
171 All other users will be mapped to their remote credential.
175 remote access by root will be mapped to that credential instead of 65534:65533.
179 all users (including root) will be mapped to that credential in
183 .Fl sec Li = Sy flavor1:flavor2...
185 specifies a colon separated list of acceptable security flavors to be
186 used for remote access.
187 Supported security flavors are sys, krb5, krb5i and krb5p.
188 If multiple flavors are listed, they should be ordered with the most
189 preferred flavor first.
190 If this option is not present,
191 the default security flavor list of just sys is used.
195 option specifies that the file system should be exported read-only
196 (default read/write).
201 in an effort to be backward compatible with older export file formats.
204 exports strictly according to the spec (RFC 2054 and RFC 2055) can
208 However, this flag in itself allows r/w access to all files in
209 the file system, not requiring reserved ports and not remapping UIDs.
211 is only provided to conform to the spec, and should normally not be used.
220 .Fl mapall No = Sy nobody
224 Note that only one file system can be
226 exported on a server.
230 .Fl index No = Pa file
232 option can be used to specify a file whose handle will be returned if
233 a directory is looked up using the public filehandle
235 This is to mimic the behavior of URLs.
238 option is specified, a directory filehandle will be returned as usual.
241 option only makes sense in combination with the
252 export options are used to require the client to use TLS for the mount(s)
254 For NFS mounts using TLS to work,
256 must be running on the server.
257 .Bd -filled -offset indent
259 requires that the client use TLS.
262 requires that the client use TLS and provide a verifiable X.509 certificate
263 during TLS handshake.
266 requires that the client use TLS and provide a verifiable X.509 certificate.
267 The otherName component of the certificate's subjAltName must have a
268 an OID of 1.3.6.1.4.1.2238.1.1.1 and a UTF8 string of the form
271 will be translated to the credentials of the specified user in the same
276 is normally a username is the server's password database and
278 is the DNS domain name for the server.
279 All RPCs will be performed using these credentials instead of the
280 ones in the RPC header in a manner similar to
282 .Fl mapall Li = Sy user .
286 If none of these three flags are specified, TLS mounts are permitted but
291 option will inhibit some of the syslog diagnostics for bad lines in
293 This can be useful to avoid annoying error messages for known possible
298 The third component of a line specifies the host set to which the line applies.
299 The set may be specified in three ways.
300 The first way is to list the host name(s) separated by white space.
303 addresses may be used in place of names.)
304 The second way is to specify a
310 The third way is to specify an Internet subnetwork using a network and
311 network mask that is defined as the set of all hosts with addresses within
313 This latter approach requires less overhead within the
314 kernel and is recommended for cases where the export line refers to a
315 large number of clients within an administrative subnet.
317 The first two cases are specified by simply listing the name(s) separated
319 All names are checked to see if they are
322 first and are assumed to be hostnames otherwise.
323 Using the full domain specification for a hostname can normally
324 circumvent the problem of a host that has the same name as a netgroup.
325 The third case is specified by the flag
327 .Fl network Li = Sy netname Op Li / Ar prefixlength
331 .Fl mask No = Sy netmask .
333 The netmask may be specified either by attaching a
337 option, or by using a separate
340 If the mask is not specified, it will default to the historical mask
341 for that network class (A, B, or C; see
343 This usage is deprecated, and will elicit a warning log message.
348 Scoped IPv6 address must carry scope identifier as documented in
358 For the third form which specifies the NFSv4 tree root, the directory path
359 specifies the location within the server's file system tree which is the
360 root of the NFSv4 tree.
361 There can only be one NFSv4 root directory per server.
362 As such, all entries of this form must specify the same directory path.
363 For file systems other than ZFS,
364 this location can be any directory and does not
365 need to be within an exported file system.
366 If it is not in an exported file system, a very limited set of operations
367 are permitted, so that an NFSv4 client can traverse the tree to an
368 exported file system.
369 Although parts of the NFSv4 tree can be non-exported, the entire NFSv4 tree
370 must consist of local file systems capable of being exported via NFS.
371 All ZFS file systems in the subtree below the NFSv4 tree root must be
373 NFSv4 does not use the mount protocol and does permit clients to cross server
374 mount point boundaries, although not all clients are capable of crossing the
379 option on these line(s) specifies what security flavors may be used for
380 NFSv4 operations that do not use file handles.
381 Since these operations (SetClientID, SetClientIDConfirm, Renew, DelegPurge
382 and ReleaseLockOnwer) allocate/modify state in the server, it is possible
383 to restrict some clients to the use of the krb5[ip] security flavors,
388 This third form is meaningless for NFSv2 and NFSv3 and is ignored for them.
392 utility can be made to re-read the
394 file by sending it a hangup signal as follows:
395 .Bd -literal -offset indent
396 /etc/rc.d/mountd reload
403 output to see whether
405 logged any parsing errors in the
409 .Bl -tag -width /etc/exports -compact
411 the default remote mount-point file
419 local file system mount points, let's consider the following example:
421 .Bd -literal -offset indent
422 /usr /usr/local -maproot=0:10 friends
423 /usr -maproot=daemon grumpy.cis.uoguelph.ca 131.104.48.16
424 /usr -ro -mapall=nobody
425 /u -maproot=bin: -network 131.104.48 -mask 255.255.255.0
426 /a -network 192.168.0/24
427 /a -network 3ffe:1ce1:1:fe80::/64
428 /u2 -maproot=root friends
429 /u2 -alldirs -network cis-net -mask cis-mask
430 /cdrom -alldirs,quiet,ro -network 192.168.33.0 -mask 255.255.255.0
433 V4: / -sec=krb5:krb5i:krb5p -network 131.104.48 -mask 255.255.255.0
434 V4: / -sec=sys:krb5:krb5i:krb5p grumpy.cis.uoguelph.ca
437 The file systems rooted at
441 are exported to hosts within the
444 with users mapped to their remote credentials and
445 root mapped to UID 0 and group 10.
446 They are exported read-write and the hosts in
449 The file system rooted at
454 .Em grumpy.cis.uoguelph.ca
455 with users mapped to their remote credentials and
456 root mapped to the user and groups associated with
458 it is exported to the rest of the world as read-only with
459 all users mapped to the user and groups associated with
462 The file system rooted at
464 is exported to all hosts on the subnetwork
466 with root mapped to the UID for
468 and with no group access.
470 The file system rooted at
472 is exported to the hosts in
474 with root mapped to UID and groups
477 it is exported to all hosts on network
479 allowing mounts at any
480 directory within /u2.
482 The file system rooted at
484 is exported to the network 192.168.0.0, with a netmask of 255.255.255.0.
485 However, the netmask length in the entry for
487 is not specified through a
489 option, but through the
493 The file system rooted at
495 is also exported to the IPv6 network
496 .Li 3ffe:1ce1:1:fe80::
497 address, using the upper 64 bits as the prefix.
498 Note that, unlike with IPv4 network addresses, the specified network
499 address must be complete, and not just contain the upper bits.
500 With IPv6 addresses, the
502 option must not be used.
504 The file system rooted at
506 will be exported read-only to the entire network 192.168.33.0/24, including
507 all its subdirectories.
510 is the conventional mountpoint for a CD-ROM device, this export will
511 fail if no CD-ROM medium is currently mounted there since that line
512 would then attempt to export a subdirectory of the root file system
515 option which is not allowed.
518 option will then suppress the error message for this condition that
519 would normally be syslogged.
520 As soon as an actual CD-ROM is going to be mounted,
524 about this situation, and the
526 file system will be exported as intended.
527 Note that without using the
529 option, the export would always succeed.
530 While there is no CD-ROM medium mounted under
532 it would export the (normally empty) directory
534 of the root file system instead.
536 The file system rooted at
538 will be exported using Kerberos 5 authentication and will require
539 integrity protected messages for all accesses.
540 The file system rooted at
542 will also be exported using Kerberos 5 authentication and all messages
543 used to access it will be encrypted.
545 For the experimental server, the NFSv4 tree is rooted at ``/'',
546 and any client within the 131.104.48 subnet is permitted to perform NFSv4 state
547 operations on the server, so long as valid Kerberos credentials are provided.
548 The machine grumpy.cis.uoguelph.ca is permitted to perform NFSv4 state
549 operations on the server using AUTH_SYS credentials, as well as Kerberos ones.
551 In the following example some directories are exported as NFSv3 and NFSv4:
552 .Bd -literal -offset indent
554 /wingsdl/nfsv4/usr-ports -maproot=root -network 172.16.0.0 -mask 255.255.0.0
555 /wingsdl/nfsv4/clasper -maproot=root clasper
558 Only one V4: line is needed or allowed to declare where NFSv4 is
560 The other lines declare specific exported directories with
561 their absolute paths given in /etc/exports.
563 The exported directories' paths are used for both v3 and v4.
564 However, they are interpreted differently for v3 and v4.
565 A client mount command for usr-ports would use the server-absolute name when
567 .Bd -literal -offset indent
568 mount server:/wingsdl/nfsv4/usr-ports /mnt/tmp
571 A mount command using NFSv4 would use the path relative to the NFSv4
573 .Bd -literal -offset indent
574 mount server:/usr-ports /mnt/tmp
577 This also differentiates which version you want if the client can do
579 The former will only ever do a v3 mount and the latter will only ever
582 Note that due to different mount behavior between NFSv3 and NFSv4 a
583 NFSv4 mount request for a directory that the client does not have
584 permission for will succeed and read/write access will fail
585 afterwards, whereas NFSv3 rejects the mount request.
594 The implementation is based on the following documents:
598 .%T "Network File System Protocol Specification, Appendix A, RFC 1094"
602 .%T "NFS: Network File System Version 3, Appendix I, RFC 1813"
606 .%T "Towards Remote Procedure Call Encryption By Default, RFC nnnn"
610 The export options are tied to the local mount points in the kernel and
611 must be non-contradictory for any exported subdirectory of the local
613 It is recommended that all exported directories within the same server
614 file system be specified on adjacent lines going down the tree.
615 You cannot specify a hostname that is also the name of a netgroup.
616 Specifying the full domain specification for a hostname can normally
617 circumvent the problem.