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.\" 4. 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 December 23, 2012 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. 95Thus, all the above export line(s) should be considered to have the 96.Fl alldirs 97flag, even if the line is specified without it. 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. 134.Pp 135.Sm off 136.Fl maproot Li = Sy user:group1:group2:... 137.Sm on 138The colon separated list is used to specify the precise credential 139to be used for remote access by root. 140The elements of the list may be either names or numbers. 141Note that user: should be used to distinguish a credential containing 142no groups from a complete credential for that user. 143.Pp 144.Sm off 145.Fl mapall Li = Sy user 146.Sm on 147or 148.Sm off 149.Fl mapall Li = Sy user:group1:group2:... 150.Sm on 151specifies a mapping for all client UIDs (including root) 152using the same semantics as 153.Fl maproot . 154.Pp 155The option 156.Fl r 157is a synonym for 158.Fl maproot 159in an effort to be backward compatible with older export file formats. 160.Pp 161In the absence of 162.Fl maproot 163and 164.Fl mapall 165options, remote accesses by root will result in using a credential of -2:-2. 166All other users will be mapped to their remote credential. 167If a 168.Fl maproot 169option is given, 170remote access by root will be mapped to that credential instead of -2:-2. 171If a 172.Fl mapall 173option is given, 174all users (including root) will be mapped to that credential in 175place of their own. 176.Pp 177.Sm off 178.Fl sec Li = Sy flavor1:flavor2... 179.Sm on 180specifies a colon separated list of acceptable security flavors to be 181used for remote access. 182Supported security flavors are sys, krb5, krb5i and krb5p. 183If multiple flavors are listed, they should be ordered with the most 184preferred flavor first. 185If this option is not present, 186the default security flavor list of just sys is used. 187.Pp 188The 189.Fl ro 190option specifies that the file system should be exported read-only 191(default read/write). 192The option 193.Fl o 194is a synonym for 195.Fl ro 196in an effort to be backward compatible with older export file formats. 197.Pp 198.Tn WebNFS 199exports strictly according to the spec (RFC 2054 and RFC 2055) can 200be done with the 201.Fl public 202flag. 203However, this flag in itself allows r/w access to all files in 204the file system, not requiring reserved ports and not remapping UIDs. 205It 206is only provided to conform to the spec, and should normally not be used. 207For a 208.Tn WebNFS 209export, 210use the 211.Fl webnfs 212flag, which implies 213.Fl public , 214.Sm off 215.Fl mapall No = Sy nobody 216.Sm on 217and 218.Fl ro . 219Note that only one file system can be 220.Tn WebNFS 221exported on a server. 222.Pp 223A 224.Sm off 225.Fl index No = Pa file 226.Sm on 227option can be used to specify a file whose handle will be returned if 228a directory is looked up using the public filehandle 229.Pq Tn WebNFS . 230This is to mimic the behavior of URLs. 231If no 232.Fl index 233option is specified, a directory filehandle will be returned as usual. 234The 235.Fl index 236option only makes sense in combination with the 237.Fl public 238or 239.Fl webnfs 240flags. 241.Pp 242Specifying the 243.Fl quiet 244option will inhibit some of the syslog diagnostics for bad lines in 245.Pa /etc/exports . 246This can be useful to avoid annoying error messages for known possible 247problems (see 248.Sx EXAMPLES 249below). 250.Pp 251The third component of a line specifies the host set to which the line applies. 252The set may be specified in three ways. 253The first way is to list the host name(s) separated by white space. 254(Standard Internet 255.Dq dot 256addresses may be used in place of names.) 257The second way is to specify a 258.Dq netgroup 259as defined in the 260.Pa netgroup 261file (see 262.Xr netgroup 5 ) . 263The third way is to specify an Internet subnetwork using a network and 264network mask that is defined as the set of all hosts with addresses within 265the subnetwork. 266This latter approach requires less overhead within the 267kernel and is recommended for cases where the export line refers to a 268large number of clients within an administrative subnet. 269.Pp 270The first two cases are specified by simply listing the name(s) separated 271by whitespace. 272All names are checked to see if they are 273.Dq netgroup 274names 275first and are assumed to be hostnames otherwise. 276Using the full domain specification for a hostname can normally 277circumvent the problem of a host that has the same name as a netgroup. 278The third case is specified by the flag 279.Sm off 280.Fl network Li = Sy netname Op Li / Ar prefixlength 281.Sm on 282and optionally 283.Sm off 284.Fl mask No = Sy netmask . 285.Sm on 286The netmask may be specified either by attaching a 287.Ar prefixlength 288to the 289.Fl network 290option, or by using a separate 291.Fl mask 292option. 293If the mask is not specified, it will default to the mask for that network 294class (A, B or C; see 295.Xr inet 4 ) . 296See the 297.Sx EXAMPLES 298section below. 299.Pp 300Scoped IPv6 address must carry scope identifier as documented in 301.Xr inet6 4 . 302For example, 303.Dq Li fe80::%re2/10 304is used to specify 305.Li fe80::/10 306on 307.Li re2 308interface. 309.Pp 310For the third form which specifies the NFSv4 tree root, the directory path 311specifies the location within the server's file system tree which is the 312root of the NFSv4 tree. 313All entries of this form must specify the same directory path. 314For file systems other than ZFS, 315this location can be any directory and does not 316need to be within an exported file system. If it is not in an exported 317file system, a very limited set of operations are permitted, so that an 318NFSv4 client can traverse the tree to an exported file system. 319Although parts of the NFSv4 tree can be non-exported, the entire NFSv4 tree 320must consist of local file systems capable of being exported via NFS. 321All ZFS file systems in the subtree below the NFSv4 tree root must be 322exported. 323NFSv4 does not use the mount protocol and does permit clients to cross server 324mount point boundaries, although not all clients are capable of crossing the 325mount points. 326.Pp 327The 328.Fl sec 329option on these line(s) specifies what security flavors may be used for 330NFSv4 operations that do not use file handles. Since these operations 331(SetClientID, SetClientIDConfirm, Renew, DelegPurge and ReleaseLockOnwer) 332allocate/modify state in the server, it is possible to restrict some clients to 333the use of the krb5[ip] security flavors, via this option. 334See the 335.Sx EXAMPLES 336section below. 337This third form is meaningless for NFSv2 and NFSv3 and is ignored for them. 338.Pp 339The 340.Xr mountd 8 341utility can be made to re-read the 342.Nm 343file by sending it a hangup signal as follows: 344.Bd -literal -offset indent 345/etc/rc.d/mountd reload 346.Ed 347.Pp 348After sending the 349.Dv SIGHUP , 350check the 351.Xr syslogd 8 352output to see whether 353.Xr mountd 8 354logged any parsing errors in the 355.Nm 356file. 357.Sh FILES 358.Bl -tag -width /etc/exports -compact 359.It Pa /etc/exports 360the default remote mount-point file 361.El 362.Sh EXAMPLES 363.Bd -literal -offset indent 364/usr /usr/local -maproot=0:10 friends 365/usr -maproot=daemon grumpy.cis.uoguelph.ca 131.104.48.16 366/usr -ro -mapall=nobody 367/u -maproot=bin: -network 131.104.48 -mask 255.255.255.0 368/a -network 192.168.0/24 369/a -network 3ffe:1ce1:1:fe80::/64 370/u2 -maproot=root friends 371/u2 -alldirs -network cis-net -mask cis-mask 372/cdrom -alldirs,quiet,ro -network 192.168.33.0 -mask 255.255.255.0 373/private -sec=krb5i 374/secret -sec=krb5p 375V4: / -sec=krb5:krb5i:krb5p -network 131.104.48 -mask 255.255.255.0 376V4: / -sec=sys:krb5:krb5i:krb5p grumpy.cis.uoguelph.ca 377.Ed 378.Pp 379Given that 380.Pa /usr , /u , /a 381and 382.Pa /u2 383are 384local file system mount points, the above example specifies the following: 385.Pp 386The file system rooted at 387.Pa /usr 388is exported to hosts 389.Em friends 390where friends is specified in the netgroup file 391with users mapped to their remote credentials and 392root mapped to UID 0 and group 10. 393It is exported read-write and the hosts in 394.Dq friends 395can mount either 396.Pa /usr 397or 398.Pa /usr/local . 399It is exported to 400.Em 131.104.48.16 401and 402.Em grumpy.cis.uoguelph.ca 403with users mapped to their remote credentials and 404root mapped to the user and groups associated with 405.Dq daemon ; 406it is exported to the rest of the world as read-only with 407all users mapped to the user and groups associated with 408.Dq nobody . 409.Pp 410The file system rooted at 411.Pa /u 412is exported to all hosts on the subnetwork 413.Em 131.104.48 414with root mapped to the UID for 415.Dq bin 416and with no group access. 417.Pp 418The file system rooted at 419.Pa /u2 420is exported to the hosts in 421.Dq friends 422with root mapped to UID and groups 423associated with 424.Dq root ; 425it is exported to all hosts on network 426.Dq cis-net 427allowing mounts at any 428directory within /u2. 429.Pp 430The file system rooted at 431.Pa /a 432is exported to the network 192.168.0.0, with a netmask of 255.255.255.0. 433However, the netmask length in the entry for 434.Pa /a 435is not specified through a 436.Fl mask 437option, but through the 438.Li / Ns Ar prefix 439notation. 440.Pp 441The file system rooted at 442.Pa /a 443is also exported to the IPv6 network 444.Li 3ffe:1ce1:1:fe80:: 445address, using the upper 64 bits as the prefix. 446Note that, unlike with IPv4 network addresses, the specified network 447address must be complete, and not just contain the upper bits. 448With IPv6 addresses, the 449.Fl mask 450option must not be used. 451.Pp 452The file system rooted at 453.Pa /cdrom 454will be exported read-only to the entire network 192.168.33.0/24, including 455all its subdirectories. 456Since 457.Pa /cdrom 458is the conventional mountpoint for a CD-ROM device, this export will 459fail if no CD-ROM medium is currently mounted there since that line 460would then attempt to export a subdirectory of the root file system 461with the 462.Fl alldirs 463option which is not allowed. 464The 465.Fl quiet 466option will then suppress the error message for this condition that 467would normally be syslogged. 468As soon as an actual CD-ROM is going to be mounted, 469.Xr mount 8 470will notify 471.Xr mountd 8 472about this situation, and the 473.Pa /cdrom 474file system will be exported as intended. 475Note that without using the 476.Fl alldirs 477option, the export would always succeed. 478While there is no CD-ROM medium mounted under 479.Pa /cdrom , 480it would export the (normally empty) directory 481.Pa /cdrom 482of the root file system instead. 483.Pp 484The file system rooted at 485.Pa /private 486will be exported using Kerberos 5 authentication and will require 487integrity protected messages for all accesses. 488The file system rooted at 489.Pa /secret 490will also be exported using Kerberos 5 authentication and all messages 491used to access it will be encrypted. 492.Pp 493For the experimental server, the NFSv4 tree is rooted at ``/'', 494and any client within the 131.104.48 subnet is permitted to perform NFSv4 state 495operations on the server, so long as valid Kerberos credentials are provided. 496The machine grumpy.cis.uoguelph.ca is permitted to perform NFSv4 state 497operations on the server using AUTH_SYS credentials, as well as Kerberos ones. 498.Sh SEE ALSO 499.Xr nfsv4 4 , 500.Xr netgroup 5 , 501.Xr mountd 8 , 502.Xr nfsd 8 , 503.Xr showmount 8 504.Sh BUGS 505The export options are tied to the local mount points in the kernel and 506must be non-contradictory for any exported subdirectory of the local 507server mount point. 508It is recommended that all exported directories within the same server 509file system be specified on adjacent lines going down the tree. 510You cannot specify a hostname that is also the name of a netgroup. 511Specifying the full domain specification for a hostname can normally 512circumvent the problem. 513