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.\" @(#)exports.5 8.3 (Berkeley) 3/29/95 29.\" $FreeBSD$ 30.\" 31.Dd May 20, 2017 32.Dt EXPORTS 5 33.Os 34.Sh NAME 35.Nm exports 36.Nd define remote mount points for 37.Tn NFS 38mount requests 39.Sh SYNOPSIS 40.Nm 41.Sh DESCRIPTION 42The 43.Nm 44file specifies remote mount points for the 45.Tn NFS 46mount protocol per the 47.Tn NFS 48server specification; see 49.%T "Network File System Protocol Specification" , 50RFC1094, Appendix A and 51.%T "NFS: Network File System Version 3 Specification" , 52Appendix I. 53.Pp 54Each line in the file 55(other than comment lines that begin with a #) 56specifies the mount point(s) and export flags within one local server 57file system or the NFSv4 tree root for one or more hosts. 58A long line may be split over several lines by ending all but the 59last line with a backslash 60.Pq Ql \e . 61A host may be specified only once for each local file or the NFSv4 tree root on the 62server and there may be only one default entry for each server 63file system that applies to all other hosts. 64The latter exports the file system to the 65.Dq world 66and should 67be used only when the file system contains public information. 68.Pp 69In a mount entry, 70the first field(s) specify the directory path(s) within a server file system 71that can be mounted on by the corresponding client(s). 72There are three forms of this specification. 73The first is to list all mount points as absolute 74directory paths separated by whitespace. 75This list of directory paths should be considered an 76.Dq administrative control , 77since it is only enforced by the 78.Xr mountd 8 79daemon and not the kernel. 80As such, it only applies to NFSv2 and NFSv3 mounts and only 81with respect to the client's use of the mount protocol. 82The second is to specify the pathname of the root of the file system 83followed by the 84.Fl alldirs 85flag; 86this form allows the host(s) to mount at any point within the file system, 87including regular files if the 88.Fl r 89option is used on 90.Xr mountd 8 . 91Because NFSv4 does not use the mount protocol, 92the 93.Dq administrative controls 94are not applied and all directories within this server 95file system are mountable via NFSv4 even if the 96.Fl alldirs 97flag has not been specified. 98The third form has the string ``V4:'' followed by a single absolute path 99name, to specify the NFSv4 tree root. 100This line does not export any file system, but simply marks where the root 101of the server's directory tree is for NFSv4 clients. 102The exported file systems for NFSv4 are specified via the other lines 103in the 104.Nm 105file in the same way as for NFSv2 and NFSv3. 106The pathnames must not have any symbolic links in them and should not have 107any 108.Dq Pa \&. 109or 110.Dq Pa .. 111components. 112Mount points for a file system may appear on multiple lines each with 113different sets of hosts and export options. 114.Pp 115The second component of a line specifies how the file system is to be 116exported to the host set. 117The option flags specify whether the file system 118is exported read-only or read-write and how the client UID is mapped to 119user credentials on the server. 120For the NFSv4 tree root, the only option that can be specified in this 121section is 122.Fl sec . 123.Pp 124Export options are specified as follows: 125.Pp 126.Sm off 127.Fl maproot Li = Sy user 128.Sm on 129The credential of the specified user is used for remote access by root. 130The credential includes all the groups to which the user is a member 131on the local machine (see 132.Xr id 1 ) . 133The user may be specified by name or number. 134The user string may be quoted, or use backslash escaping. 135.Pp 136.Sm off 137.Fl maproot Li = Sy user:group1:group2:... 138.Sm on 139The colon separated list is used to specify the precise credential 140to be used for remote access by root. 141The elements of the list may be either names or numbers. 142Note that user: should be used to distinguish a credential containing 143no groups from a complete credential for that user. 144The group names may be quoted, or use backslash escaping. 145.Pp 146.Sm off 147.Fl mapall Li = Sy user 148.Sm on 149or 150.Sm off 151.Fl mapall Li = Sy user:group1:group2:... 152.Sm on 153specifies a mapping for all client UIDs (including root) 154using the same semantics as 155.Fl maproot . 156.Pp 157The option 158.Fl r 159is a synonym for 160.Fl maproot 161in an effort to be backward compatible with older export file formats. 162.Pp 163In the absence of 164.Fl maproot 165and 166.Fl mapall 167options, remote accesses by root will result in using a credential of 65534:65533. 168All other users will be mapped to their remote credential. 169If a 170.Fl maproot 171option is given, 172remote access by root will be mapped to that credential instead of 65534:65533. 173If a 174.Fl mapall 175option is given, 176all users (including root) will be mapped to that credential in 177place of their own. 178.Pp 179.Sm off 180.Fl sec Li = Sy flavor1:flavor2... 181.Sm on 182specifies a colon separated list of acceptable security flavors to be 183used for remote access. 184Supported security flavors are sys, krb5, krb5i and krb5p. 185If multiple flavors are listed, they should be ordered with the most 186preferred flavor first. 187If this option is not present, 188the default security flavor list of just sys is used. 189.Pp 190The 191.Fl ro 192option specifies that the file system should be exported read-only 193(default read/write). 194The option 195.Fl o 196is a synonym for 197.Fl ro 198in an effort to be backward compatible with older export file formats. 199.Pp 200.Tn WebNFS 201exports strictly according to the spec (RFC 2054 and RFC 2055) can 202be done with the 203.Fl public 204flag. 205However, this flag in itself allows r/w access to all files in 206the file system, not requiring reserved ports and not remapping UIDs. 207It 208is only provided to conform to the spec, and should normally not be used. 209For a 210.Tn WebNFS 211export, 212use the 213.Fl webnfs 214flag, which implies 215.Fl public , 216.Sm off 217.Fl mapall No = Sy nobody 218.Sm on 219and 220.Fl ro . 221Note that only one file system can be 222.Tn WebNFS 223exported on a server. 224.Pp 225A 226.Sm off 227.Fl index No = Pa file 228.Sm on 229option can be used to specify a file whose handle will be returned if 230a directory is looked up using the public filehandle 231.Pq Tn WebNFS . 232This is to mimic the behavior of URLs. 233If no 234.Fl index 235option is specified, a directory filehandle will be returned as usual. 236The 237.Fl index 238option only makes sense in combination with the 239.Fl public 240or 241.Fl webnfs 242flags. 243.Pp 244Specifying the 245.Fl quiet 246option will inhibit some of the syslog diagnostics for bad lines in 247.Pa /etc/exports . 248This can be useful to avoid annoying error messages for known possible 249problems (see 250.Sx EXAMPLES 251below). 252.Pp 253The third component of a line specifies the host set to which the line applies. 254The set may be specified in three ways. 255The first way is to list the host name(s) separated by white space. 256(Standard Internet 257.Dq dot 258addresses may be used in place of names.) 259The second way is to specify a 260.Dq netgroup 261as defined in the 262.Pa netgroup 263file (see 264.Xr netgroup 5 ) . 265The third way is to specify an Internet subnetwork using a network and 266network mask that is defined as the set of all hosts with addresses within 267the subnetwork. 268This latter approach requires less overhead within the 269kernel and is recommended for cases where the export line refers to a 270large number of clients within an administrative subnet. 271.Pp 272The first two cases are specified by simply listing the name(s) separated 273by whitespace. 274All names are checked to see if they are 275.Dq netgroup 276names 277first and are assumed to be hostnames otherwise. 278Using the full domain specification for a hostname can normally 279circumvent the problem of a host that has the same name as a netgroup. 280The third case is specified by the flag 281.Sm off 282.Fl network Li = Sy netname Op Li / Ar prefixlength 283.Sm on 284and optionally 285.Sm off 286.Fl mask No = Sy netmask . 287.Sm on 288The netmask may be specified either by attaching a 289.Ar prefixlength 290to the 291.Fl network 292option, or by using a separate 293.Fl mask 294option. 295If the mask is not specified, it will default to the mask for that network 296class (A, B or C; see 297.Xr inet 4 ) . 298See the 299.Sx EXAMPLES 300section below. 301.Pp 302Scoped IPv6 address must carry scope identifier as documented in 303.Xr inet6 4 . 304For example, 305.Dq Li fe80::%re2/10 306is used to specify 307.Li fe80::/10 308on 309.Li re2 310interface. 311.Pp 312For the third form which specifies the NFSv4 tree root, the directory path 313specifies the location within the server's file system tree which is the 314root of the NFSv4 tree. 315There can only be one NFSv4 root directory per server. 316As such, all entries of this form must specify the same directory path. 317For file systems other than ZFS, 318this location can be any directory and does not 319need to be within an exported file system. If it is not in an exported 320file system, a very limited set of operations are permitted, so that an 321NFSv4 client can traverse the tree to an exported file system. 322Although parts of the NFSv4 tree can be non-exported, the entire NFSv4 tree 323must consist of local file systems capable of being exported via NFS. 324All ZFS file systems in the subtree below the NFSv4 tree root must be 325exported. 326NFSv4 does not use the mount protocol and does permit clients to cross server 327mount point boundaries, although not all clients are capable of crossing the 328mount points. 329.Pp 330The 331.Fl sec 332option on these line(s) specifies what security flavors may be used for 333NFSv4 operations that do not use file handles. Since these operations 334(SetClientID, SetClientIDConfirm, Renew, DelegPurge and ReleaseLockOnwer) 335allocate/modify state in the server, it is possible to restrict some clients to 336the use of the krb5[ip] security flavors, via this option. 337See the 338.Sx EXAMPLES 339section below. 340This third form is meaningless for NFSv2 and NFSv3 and is ignored for them. 341.Pp 342The 343.Xr mountd 8 344utility can be made to re-read the 345.Nm 346file by sending it a hangup signal as follows: 347.Bd -literal -offset indent 348/etc/rc.d/mountd reload 349.Ed 350.Pp 351After sending the 352.Dv SIGHUP , 353check the 354.Xr syslogd 8 355output to see whether 356.Xr mountd 8 357logged any parsing errors in the 358.Nm 359file. 360.Sh FILES 361.Bl -tag -width /etc/exports -compact 362.It Pa /etc/exports 363the default remote mount-point file 364.El 365.Sh EXAMPLES 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 255.255.255.0 376/private -sec=krb5i 377/secret -sec=krb5p 378V4: / -sec=krb5:krb5i:krb5p -network 131.104.48 -mask 255.255.255.0 379V4: / -sec=sys:krb5:krb5i:krb5p grumpy.cis.uoguelph.ca 380.Ed 381.Pp 382Given that 383.Pa /usr , /u , /a 384and 385.Pa /u2 386are 387local file system mount points, the above example specifies the following: 388.Pp 389The file system rooted at 390.Pa /usr 391is exported to hosts 392.Em friends 393where friends is specified in the netgroup file 394with users mapped to their remote credentials and 395root mapped to UID 0 and group 10. 396It is exported read-write and the hosts in 397.Dq friends 398can mount either 399.Pa /usr 400or 401.Pa /usr/local . 402It is exported to 403.Em 131.104.48.16 404and 405.Em grumpy.cis.uoguelph.ca 406with users mapped to their remote credentials and 407root mapped to the user and groups associated with 408.Dq daemon ; 409it is exported to the rest of the world as read-only with 410all users mapped to the user and groups associated with 411.Dq nobody . 412.Pp 413The file system rooted at 414.Pa /u 415is exported to all hosts on the subnetwork 416.Em 131.104.48 417with root mapped to the UID for 418.Dq bin 419and with no group access. 420.Pp 421The file system rooted at 422.Pa /u2 423is exported to the hosts in 424.Dq friends 425with root mapped to UID and groups 426associated with 427.Dq root ; 428it is exported to all hosts on network 429.Dq cis-net 430allowing mounts at any 431directory within /u2. 432.Pp 433The file system rooted at 434.Pa /a 435is exported to the network 192.168.0.0, with a netmask of 255.255.255.0. 436However, the netmask length in the entry for 437.Pa /a 438is not specified through a 439.Fl mask 440option, but through the 441.Li / Ns Ar prefix 442notation. 443.Pp 444The file system rooted at 445.Pa /a 446is also exported to the IPv6 network 447.Li 3ffe:1ce1:1:fe80:: 448address, using the upper 64 bits as the prefix. 449Note that, unlike with IPv4 network addresses, the specified network 450address must be complete, and not just contain the upper bits. 451With IPv6 addresses, the 452.Fl mask 453option must not be used. 454.Pp 455The file system rooted at 456.Pa /cdrom 457will be exported read-only to the entire network 192.168.33.0/24, including 458all its subdirectories. 459Since 460.Pa /cdrom 461is the conventional mountpoint for a CD-ROM device, this export will 462fail if no CD-ROM medium is currently mounted there since that line 463would then attempt to export a subdirectory of the root file system 464with the 465.Fl alldirs 466option which is not allowed. 467The 468.Fl quiet 469option will then suppress the error message for this condition that 470would normally be syslogged. 471As soon as an actual CD-ROM is going to be mounted, 472.Xr mount 8 473will notify 474.Xr mountd 8 475about this situation, and the 476.Pa /cdrom 477file system will be exported as intended. 478Note that without using the 479.Fl alldirs 480option, the export would always succeed. 481While there is no CD-ROM medium mounted under 482.Pa /cdrom , 483it would export the (normally empty) directory 484.Pa /cdrom 485of the root file system instead. 486.Pp 487The file system rooted at 488.Pa /private 489will be exported using Kerberos 5 authentication and will require 490integrity protected messages for all accesses. 491The file system rooted at 492.Pa /secret 493will also be exported using Kerberos 5 authentication and all messages 494used to access it will be encrypted. 495.Pp 496For the experimental server, the NFSv4 tree is rooted at ``/'', 497and any client within the 131.104.48 subnet is permitted to perform NFSv4 state 498operations on the server, so long as valid Kerberos credentials are provided. 499The machine grumpy.cis.uoguelph.ca is permitted to perform NFSv4 state 500operations on the server using AUTH_SYS credentials, as well as Kerberos ones. 501.Sh SEE ALSO 502.Xr nfsv4 4 , 503.Xr netgroup 5 , 504.Xr mountd 8 , 505.Xr nfsd 8 , 506.Xr showmount 8 507.Sh BUGS 508The export options are tied to the local mount points in the kernel and 509must be non-contradictory for any exported subdirectory of the local 510server mount point. 511It is recommended that all exported directories within the same server 512file system be specified on adjacent lines going down the tree. 513You cannot specify a hostname that is also the name of a netgroup. 514Specifying the full domain specification for a hostname can normally 515circumvent the problem. 516