1.\" Copyright (c) 1989, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.Dd December 21, 2023 29.Dt EXPORTS 5 30.Os 31.Sh NAME 32.Nm exports 33.Nd define remote mount points for 34.Tn NFS 35mount requests 36.Sh SYNOPSIS 37.Nm 38.Sh DESCRIPTION 39The 40.Nm 41file specifies remote mount points for the 42.Tn NFS 43mount protocol per the 44.Tn NFS 45server specification; see 46.%T "Network File System Protocol Specification" , 47RFC1094, Appendix A and 48.%T "NFS: Network File System Version 3 Specification" , 49Appendix I. 50.Pp 51Each line in the file 52(other than comment lines that begin with a #) 53specifies the mount point(s) and export flags within one local server 54file system or the NFSv4 tree root for one or more hosts. 55A long line may be split over several lines by ending all but the 56last line with a backslash 57.Pq Ql \e . 58A host may be specified only once for each local file or the NFSv4 tree root on the 59server and there may be only one default entry for each server 60file system that applies to all other hosts. 61The latter exports the file system to the 62.Dq world 63and should 64be used only when the file system contains public information. 65.Pp 66In a mount entry, 67the first field(s) specify the directory path(s) within a server file system 68that can be mounted on by the corresponding client(s). 69There are three forms of this specification. 70The first is to list all mount points as absolute 71directory paths separated by whitespace. 72This list of directory paths should be considered an 73.Dq administrative control , 74since it is only enforced by the 75.Xr mountd 8 76daemon and not the kernel. 77As such, it only applies to NFSv2 and NFSv3 mounts and only 78with respect to the client's use of the mount protocol. 79The second is to specify the pathname of the root of the file system 80followed by the 81.Fl alldirs 82flag; 83this form allows the host(s) to mount at any point within the file system, 84including regular files if the 85.Fl r 86option is used on 87.Xr mountd 8 . 88Because NFSv4 does not use the mount protocol, 89the 90.Dq administrative controls 91are not applied and all directories within this server 92file system are mountable via NFSv4 even if the 93.Fl alldirs 94flag has not been specified. 95The third form has the string ``V4:'' followed by a single absolute path 96name, to specify the NFSv4 tree root. 97This line does not export any file system, but simply marks where the root 98of the server's directory tree is for NFSv4 clients. 99The exported file systems for NFSv4 are specified via the other lines 100in the 101.Nm 102file in the same way as for NFSv2 and NFSv3. 103The pathnames must not have any symbolic links in them and should not have 104any 105.Dq Pa \&. 106or 107.Dq Pa .. 108components. 109Pathnames are decoded by 110.Xr strunvis 3 111allowing special characters to be included in the directory name(s). 112In particular, whitespace, such as embedded blanks in directory names 113can be handled. 114For example, a blank can be encoded as \(rs040. 115.Xr vis 1 116with the 117.Fl M 118option may be used to encode directory name(s) with embedded special 119characters. 120Mount points for a file system may appear on multiple lines each with 121different sets of hosts and export options. 122.Pp 123The second component of a line specifies how the file system is to be 124exported to the host set. 125The option flags specify whether the file system 126is exported read-only or read-write and how the client UID is mapped to 127user credentials on the server. 128For the NFSv4 tree root, the only options that can be specified in this 129section are ones related to security: 130.Fl sec , 131.Fl tls , 132.Fl tlscert 133and 134.Fl tlscertuser . 135.Pp 136Export options are specified as follows: 137.Pp 138.Sm off 139.Fl maproot Li = Sy user 140.Sm on 141The credential of the specified user is used for remote access by root. 142The credential includes all the groups to which the user is a member 143on the local machine (see 144.Xr id 1 ) . 145The user may be specified by name or number. 146The user string may be quoted, or use backslash escaping. 147.Pp 148.Sm off 149.Fl maproot Li = Sy user:group1:group2:... 150.Sm on 151The colon separated list is used to specify the precise credential 152to be used for remote access by root. 153The elements of the list may be either names or numbers. 154Note that user: should be used to distinguish a credential containing 155no groups from a complete credential for that user. 156The group names may be quoted, or use backslash escaping. 157.Pp 158.Sm off 159.Fl mapall Li = Sy user 160.Sm on 161or 162.Sm off 163.Fl mapall Li = Sy user:group1:group2:... 164.Sm on 165specifies a mapping for all client UIDs (including root) 166using the same semantics as 167.Fl maproot . 168.Pp 169The option 170.Fl r 171is a synonym for 172.Fl maproot 173in an effort to be backward compatible with older export file formats. 174.Pp 175In the absence of 176.Fl maproot 177and 178.Fl mapall 179options, remote accesses by root will result in using a credential of 65534:65533. 180All other users will be mapped to their remote credential. 181If a 182.Fl maproot 183option is given, 184remote access by root will be mapped to that credential instead of 65534:65533. 185If a 186.Fl mapall 187option is given, 188all users (including root) will be mapped to that credential in 189place of their own. 190.Pp 191.Sm off 192.Fl sec Li = Sy flavor1:flavor2... 193.Sm on 194specifies a colon separated list of acceptable security flavors to be 195used for remote access. 196Supported security flavors are sys, krb5, krb5i and krb5p. 197If multiple flavors are listed, they should be ordered with the most 198preferred flavor first. 199If this option is not present, 200the default security flavor list of just sys is used. 201.Pp 202The 203.Fl ro 204option specifies that the file system should be exported read-only 205(default read/write). 206The option 207.Fl o 208is a synonym for 209.Fl ro 210in an effort to be backward compatible with older export file formats. 211.Pp 212.Tn WebNFS 213exports strictly according to the spec (RFC 2054 and RFC 2055) can 214be done with the 215.Fl public 216flag. 217However, this flag in itself allows r/w access to all files in 218the file system, not requiring reserved ports and not remapping UIDs. 219It 220is only provided to conform to the spec, and should normally not be used. 221For a 222.Tn WebNFS 223export, 224use the 225.Fl webnfs 226flag, which implies 227.Fl public , 228.Sm off 229.Fl mapall No = Sy nobody 230.Sm on 231and 232.Fl ro . 233Note that only one file system can be 234.Tn WebNFS 235exported on a server. 236.Pp 237A 238.Sm off 239.Fl index No = Pa file 240.Sm on 241option can be used to specify a file whose handle will be returned if 242a directory is looked up using the public filehandle 243.Pq Tn WebNFS . 244This is to mimic the behavior of URLs. 245If no 246.Fl index 247option is specified, a directory filehandle will be returned as usual. 248The 249.Fl index 250option only makes sense in combination with the 251.Fl public 252or 253.Fl webnfs 254flags. 255.Pp 256The 257.Fl tls , 258.Fl tlscert 259and 260.Fl tlscertuser 261export options are used to require the client to use TLS for the mount(s) 262per RFC NNNN. 263For NFS mounts using TLS to work, 264.Xr rpc.tlsservd 8 265must be running on the server. 266.Bd -filled -offset indent 267.Fl tls 268requires that the client use TLS. 269.br 270.Fl tlscert 271requires that the client use TLS and provide a verifiable X.509 certificate 272during TLS handshake. 273.br 274.Fl tlscertuser 275requires that the client use TLS and provide a verifiable X.509 certificate. 276The otherName component of the certificate's subjAltName must have a 277an OID of 1.3.6.1.4.1.2238.1.1.1 and a UTF8 string of the form 278.Dq user@domain . 279.Dq user@domain 280will be translated to the credentials of the specified user in the same 281manner as 282.Xr nfsuserd 8 , 283where 284.Dq user 285is normally a username is the server's password database and 286.Dq domain 287is the DNS domain name for the server. 288All RPCs will be performed using these credentials instead of the 289ones in the RPC header in a manner similar to 290.Sm off 291.Fl mapall Li = Sy user . 292.Sm on 293.Ed 294.Pp 295If none of these three flags are specified, TLS mounts are permitted but 296not required. 297.Pp 298Specifying the 299.Fl quiet 300option will inhibit some of the syslog diagnostics for bad lines in 301.Pa /etc/exports . 302This can be useful to avoid annoying error messages for known possible 303problems (see 304.Sx EXAMPLES 305below). 306.Pp 307The third component of a line specifies the host set to which the line applies. 308The set may be specified in three ways. 309The first way is to list the host name(s) separated by white space. 310(Standard Internet 311.Dq dot 312addresses may be used in place of names.) 313The second way is to specify a 314.Dq netgroup 315as defined in the 316.Pa netgroup 317file (see 318.Xr netgroup 5 ) . 319The third way is to specify an Internet subnetwork using a network and 320network mask that is defined as the set of all hosts with addresses within 321the subnetwork. 322This latter approach requires less overhead within the 323kernel and is recommended for cases where the export line refers to a 324large number of clients within an administrative subnet. 325.Pp 326The first two cases are specified by simply listing the name(s) separated 327by whitespace. 328All names are checked to see if they are 329.Dq netgroup 330names 331first and are assumed to be hostnames otherwise. 332Using the full domain specification for a hostname can normally 333circumvent the problem of a host that has the same name as a netgroup. 334The third case is specified by the flag 335.Sm off 336.Fl network Li = Sy netname Op Li / Ar prefixlength 337.Sm on 338and optionally 339.Sm off 340.Fl mask No = Sy netmask . 341.Sm on 342The netmask may be specified either by attaching a 343.Ar prefixlength 344to the 345.Fl network 346option, or by using a separate 347.Fl mask 348option. 349If the mask is not specified, it will default to the historical mask 350for that network class (A, B, or C; see 351.Xr inet 4 ) . 352This usage is deprecated, and will elicit a warning log message. 353See the 354.Sx EXAMPLES 355section below. 356.Pp 357Scoped IPv6 address must carry scope identifier as documented in 358.Xr inet6 4 . 359For example, 360.Dq Li fe80::%re2/10 361is used to specify 362.Li fe80::/10 363on 364.Li re2 365interface. 366.Pp 367For the third form which specifies the NFSv4 tree root, the directory path 368specifies the location within the server's file system tree which is the 369root of the NFSv4 tree. 370There can only be one NFSv4 root directory per server. 371As such, all entries of this form must specify the same directory path. 372For file systems other than ZFS, 373this location can be any directory and does not 374need to be within an exported file system. 375If it is not in an exported file system, a very limited set of operations 376are permitted, so that an NFSv4 client can traverse the tree to an 377exported file system. 378Although parts of the NFSv4 tree can be non-exported, the entire NFSv4 tree 379must consist of local file systems capable of being exported via NFS. 380All ZFS file systems in the subtree below the NFSv4 tree root must be 381exported. 382NFSv4 does not use the mount protocol and does permit clients to cross server 383mount point boundaries, although not all clients are capable of crossing the 384mount points. 385.Pp 386The 387.Fl sec 388option on these line(s) specifies what security flavors may be used for 389NFSv4 operations that do not use file handles. 390Since these operations (SetClientID, SetClientIDConfirm, Renew, DelegPurge 391and ReleaseLockOnwer) allocate/modify state in the server, it is possible 392to restrict some clients to the use of the krb5[ip] security flavors, 393via this option. 394See the 395.Sx EXAMPLES 396section below. 397This third form is meaningless for NFSv2 and NFSv3 and is ignored for them. 398.Pp 399The 400.Xr mountd 8 401utility can be made to re-read the 402.Nm 403file by sending it a hangup signal as follows: 404.Bd -literal -offset indent 405/etc/rc.d/mountd reload 406.Ed 407.Pp 408After sending the 409.Dv SIGHUP , 410check the 411.Xr syslogd 8 412output to see whether 413.Xr mountd 8 414logged any parsing errors in the 415.Nm 416file. 417.Sh FILES 418.Bl -tag -width /etc/exports -compact 419.It Pa /etc/exports 420the default remote mount-point file 421.El 422.Sh EXAMPLES 423Given that 424.Pa /usr , /u , /a 425and 426.Pa /u2 427are 428local file system mount points, let's consider the following example: 429.Pp 430.Bd -literal -offset indent 431/usr /usr/local -maproot=0:10 friends 432/usr -maproot=daemon grumpy.cis.uoguelph.ca 131.104.48.16 433/usr -ro -mapall=nobody 434/u -maproot=bin: -network 131.104.48 -mask 255.255.255.0 435/a -network 192.168.0/24 436/a -network 3ffe:1ce1:1:fe80::/64 437/u2 -maproot=root friends 438/u2 -alldirs -network cis-net -mask cis-mask 439/cdrom -alldirs,quiet,ro -network 192.168.33.0 -mask 255.255.255.0 440/private -sec=krb5i 441/secret -sec=krb5p 442V4: / -sec=krb5:krb5i:krb5p -network 131.104.48 -mask 255.255.255.0 443V4: / -sec=sys:krb5:krb5i:krb5p grumpy.cis.uoguelph.ca 444.Ed 445.Pp 446The file systems rooted at 447.Pa /usr 448and 449.Pa /usr/local 450are exported to hosts within the 451.Dq friends 452network group 453with users mapped to their remote credentials and 454root mapped to UID 0 and group 10. 455They are exported read-write and the hosts in 456.Dq friends . 457.Pp 458The file system rooted at 459.Pa /usr 460is exported to 461.Em 131.104.48.16 462and 463.Em grumpy.cis.uoguelph.ca 464with users mapped to their remote credentials and 465root mapped to the user and groups associated with 466.Dq daemon ; 467it is exported to the rest of the world as read-only with 468all users mapped to the user and groups associated with 469.Dq nobody . 470.Pp 471The file system rooted at 472.Pa /u 473is exported to all hosts on the subnetwork 474.Em 131.104.48 475with root mapped to the UID for 476.Dq bin 477and with no group access. 478.Pp 479The file system rooted at 480.Pa /u2 481is exported to the hosts in 482.Dq friends 483with root mapped to UID and groups 484associated with 485.Dq root ; 486it is exported to all hosts on network 487.Dq cis-net 488allowing mounts at any 489directory within /u2. 490.Pp 491The file system rooted at 492.Pa /a 493is exported to the network 192.168.0.0, with a netmask of 255.255.255.0. 494However, the netmask length in the entry for 495.Pa /a 496is not specified through a 497.Fl mask 498option, but through the 499.Li / Ns Ar prefix 500notation. 501.Pp 502The file system rooted at 503.Pa /a 504is also exported to the IPv6 network 505.Li 3ffe:1ce1:1:fe80:: 506address, using the upper 64 bits as the prefix. 507Note that, unlike with IPv4 network addresses, the specified network 508address must be complete, and not just contain the upper bits. 509With IPv6 addresses, the 510.Fl mask 511option must not be used. 512.Pp 513The file system rooted at 514.Pa /cdrom 515will be exported read-only to the entire network 192.168.33.0/24, including 516all its subdirectories. 517Since 518.Pa /cdrom 519is the conventional mountpoint for a CD-ROM device, this export will 520fail if no CD-ROM medium is currently mounted there since that line 521would then attempt to export a subdirectory of the root file system 522with the 523.Fl alldirs 524option which is not allowed. 525The 526.Fl quiet 527option will then suppress the error message for this condition that 528would normally be syslogged. 529As soon as an actual CD-ROM is going to be mounted, 530.Xr mount 8 531will notify 532.Xr mountd 8 533about this situation, and the 534.Pa /cdrom 535file system will be exported as intended. 536Note that without using the 537.Fl alldirs 538option, the export would always succeed. 539While there is no CD-ROM medium mounted under 540.Pa /cdrom , 541it would export the (normally empty) directory 542.Pa /cdrom 543of the root file system instead. 544.Pp 545The file system rooted at 546.Pa /private 547will be exported using Kerberos 5 authentication and will require 548integrity protected messages for all accesses. 549The file system rooted at 550.Pa /secret 551will also be exported using Kerberos 5 authentication and all messages 552used to access it will be encrypted. 553.Pp 554For the experimental server, the NFSv4 tree is rooted at ``/'', 555and any client within the 131.104.48 subnet is permitted to perform NFSv4 state 556operations on the server, so long as valid Kerberos credentials are provided. 557The machine grumpy.cis.uoguelph.ca is permitted to perform NFSv4 state 558operations on the server using AUTH_SYS credentials, as well as Kerberos ones. 559.Pp 560In the following example some directories are exported as NFSv3 and NFSv4: 561.Bd -literal -offset indent 562V4: /wingsdl/nfsv4 563/wingsdl/nfsv4/usr-ports -maproot=root -network 172.16.0.0 -mask 255.255.0.0 564/wingsdl/nfsv4/clasper -maproot=root clasper 565.Ed 566.Pp 567Only one V4: line is needed or allowed to declare where NFSv4 is 568rooted. 569The other lines declare specific exported directories with 570their absolute paths given in /etc/exports. 571.Pp 572The exported directories' paths are used for both v3 and v4. 573However, they are interpreted differently for v3 and v4. 574A client mount command for usr-ports would use the server-absolute name when 575using nfsv3: 576.Bd -literal -offset indent 577mount server:/wingsdl/nfsv4/usr-ports /mnt/tmp 578.Ed 579.Pp 580A mount command using NFSv4 would use the path relative to the NFSv4 581root: 582.Bd -literal -offset indent 583mount server:/usr-ports /mnt/tmp 584.Ed 585.Pp 586This also differentiates which version you want if the client can do 587both v3 and v4. 588The former will only ever do a v3 mount and the latter will only ever 589do a v4 mount. 590.Pp 591Note that due to different mount behavior between NFSv3 and NFSv4 a 592NFSv4 mount request for a directory that the client does not have 593permission for will succeed and read/write access will fail 594afterwards, whereas NFSv3 rejects the mount request. 595.Sh SEE ALSO 596.Xr vis 1 , 597.Xr strunvis 3 , 598.Xr nfsv4 4 , 599.Xr netgroup 5 , 600.Xr mountd 8 , 601.Xr nfsd 8 , 602.Xr rpc.tlsservd 8 , 603.Xr showmount 8 604.Sh STANDARDS 605The implementation is based on the following documents: 606.Bl -dash 607.It 608.Rs 609.%T "Network File System Protocol Specification, Appendix A, RFC 1094" 610.Re 611.It 612.Rs 613.%T "NFS: Network File System Version 3, Appendix I, RFC 1813" 614.Re 615.It 616.Rs 617.%T "Towards Remote Procedure Call Encryption By Default, RFC nnnn" 618.Re 619.El 620.Sh BUGS 621The export options are tied to the local mount points in the kernel and 622must be non-contradictory for any exported subdirectory of the local 623server mount point. 624It is recommended that all exported directories within the same server 625file system be specified on adjacent lines going down the tree. 626You cannot specify a hostname that is also the name of a netgroup. 627Specifying the full domain specification for a hostname can normally 628circumvent the problem. 629