1.\" $OpenBSD: exports.5,v 1.23 2016/01/08 20:26:54 zhuk Exp $ 2.\" $NetBSD: exports.5,v 1.9 1996/02/18 11:57:50 fvdl Exp $ 3.\" 4.\" Copyright (c) 1989, 1991, 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" @(#)exports.5 8.3 (Berkeley) 3/29/95 32.\" 33.Dd $Mdocdate: January 8 2016 $ 34.Dt EXPORTS 5 35.Os 36.Sh NAME 37.Nm exports 38.Nd define remote mount points for NFS mount requests 39.Sh DESCRIPTION 40The 41.Nm 42file specifies remote mount points for the NFS 43mount protocol per the NFS server specification; see 44.%T "Network File System Protocol Specification" , 45RFC 1094, Appendix A and 46.%T "NFS: Network File System Version 3 Specification" , 47RFC 1813, Appendix I. 48.Pp 49Each line in the file 50(other than comment lines that begin with a 51.Dq # ) 52specifies the mount point(s) and export flags within one local server 53filesystem for one or more hosts. 54A host may be specified only once for each local filesystem on the 55server and there may be only one default entry for each server 56filesystem that applies to all other hosts. 57The latter exports the filesystem to the 58.Dq world 59and should 60be used only when the filesystem contains public information. 61.Pp 62In a mount entry, 63the first field(s) specify the directory path(s) within a server filesystem 64that can be mounted on by the corresponding client(s). 65There are two forms of this specification. 66The first is to list all mount points as absolute 67directory paths separated by whitespace. 68The second is to specify the pathname of the root of the filesystem 69followed by the 70.Fl alldirs 71flag; 72this form allows the host(s) to mount at any point within the filesystem, 73including regular files. 74The pathnames must not have any symbolic links in them and should not have 75any 76.Dq \&. 77or 78.Dq \&.\&. 79components. 80Mount points for a filesystem may appear on multiple lines each with 81different sets of hosts and export options. 82.Pp 83The second component of a line specifies how the filesystem is to be 84exported to the host set. 85The option flags specify whether the filesystem 86is exported read-only or read-write and how the client UID is mapped to 87user credentials on the server. 88.Pp 89Export options are specified as follows: 90.Pp 91.Sm off 92.Fl maproot No = Ar user 93.Sm on 94The credential of the specified user is used for remote access by root. 95The credential includes all the groups to which the user is a member 96on the local machine (see 97.Xr id 1 ) . 98The 99.Ar user 100may be specified by name or number. 101.Pp 102.Sm off 103.Fl maproot No = Ar user:group1:group2:... 104.Sm on 105The colon separated list is used to specify the precise credential 106to be used for remote access by root. 107The elements of the list may be either names or numbers. 108Note that user: should be used to distinguish a credential containing 109no groups from a complete credential for that user. 110.Pp 111.Sm off 112.Fl mapall No = Ar user 113.Sm on 114or 115.Sm off 116.Fl mapall No = Ar user:group1:group2:... 117.Sm on 118Specifies a mapping for all client UIDs (including root) 119using the same semantics as 120.Fl maproot . 121.Pp 122The option 123.Fl r 124is a synonym for 125.Fl maproot 126in an effort to be backward compatible with older export file formats. 127.Pp 128In the absence of 129.Fl maproot 130and 131.Fl mapall 132options, remote accesses by root will result in using a credential of -2:-2. 133All other users will be mapped to their remote credential. 134If a 135.Fl maproot 136option is given, 137remote access by root will be mapped to that credential instead of -2:-2. 138If a 139.Fl mapall 140option is given, 141all users (including root) will be mapped to that credential in 142place of their own. 143.Pp 144The 145.Fl ro 146option specifies that the filesystem should be exported read-only 147(default read/write). 148The option 149.Fl o 150is a synonym for 151.Fl ro 152in an effort to be backward compatible with older export file formats. 153.Pp 154The third component of a line specifies the host set to which the line applies. 155The set may be specified in three ways. 156The first way is to list the host name(s) separated by whitespace. 157(Standard internet 158.Dq dot 159addresses may be used in place of names.) 160The second way is to specify a 161.Dq netgroup 162as defined in the netgroup file (see 163.Xr netgroup 5 ) . 164The third way is to specify an internet subnetwork using a network and 165network mask that is defined as the set of all hosts with addresses within 166the subnetwork. 167This latter approach requires less overhead within the 168kernel and is recommended for cases where the export line refers to a 169large number of clients within an administrative subnet. 170.Pp 171The first two cases are specified by simply listing the name(s) separated 172by whitespace. 173All names are checked to see if they are 174.Dq netgroup 175names 176first and are assumed to be hostnames otherwise. 177Using the full domain specification for a hostname can normally 178circumvent the problem of a host that has the same name as a netgroup. 179The third case is specified by the flag 180.Sm off 181.Fl network No = Ar netname 182.Sm on 183and optionally 184.Sm off 185.Fl mask No = Ar netmask . 186.Sm on 187If the mask is not specified, it will default to the mask for that network 188class (A, B or C; see 189.Xr inet_addr 3 ) . 190.Pp 191For example: 192.Bd -literal -offset indent 193/usr /usr/local -maproot=0:10 friends 194/usr -maproot=daemon grumpy.cis.uoguelph.ca 131.104.48.16 195/usr -ro -mapall=nobody 196/u -maproot=bin: -network=131.104.48 -mask=255.255.255.0 197/u2 -maproot=root friends 198/u2 -alldirs -network=cis-net -mask=cis-mask 199.Ed 200.Pp 201Given that 202.Pa /usr , 203.Pa /u 204and 205.Pa /u2 206are 207local filesystem mount points, the above example specifies the following: 208.Pa /usr 209is exported to hosts 210.Em friends 211where 212.Em friends 213is specified in the netgroup file 214with users mapped to their remote credentials and 215root mapped to UID 0 and GID 10. 216It is exported read-write and the hosts in 217.Dq friends 218can mount either 219.Pa /usr 220or 221.Pa /usr/local . 222It is exported to 223.Em 131.104.48.16 224and 225.Em grumpy.cis.uoguelph.ca 226with users mapped to their remote credentials and 227root mapped to the user and groups associated with 228.Dq daemon ; 229it is exported to the rest of the world as read-only with 230all users mapped to the user and groups associated with 231.Dq nobody . 232.Pp 233.Pa /u 234is exported to all hosts on the subnetwork 235.Em 131.104.48 236with root mapped to the UID for 237.Dq bin 238and with no group access. 239.Pp 240.Pa /u2 241is exported to the hosts in 242.Dq friends 243with root mapped to UID and groups 244associated with 245.Dq root ; 246it is exported to all hosts on network 247.Dq cis-net 248allowing mounts at any 249directory within /u2. 250.Sh FILES 251.Bl -tag -width /etc/exports -compact 252.It Pa /etc/exports 253default remote mount-point file 254.El 255.Sh SEE ALSO 256.Xr netgroup 5 , 257.Xr mountd 8 , 258.Xr nfsd 8 , 259.Xr showmount 8 260.Sh BUGS 261The export options are tied to the local mount points in the kernel and 262must be non-contradictory for any exported subdirectory of the local 263server mount point. 264It is recommended that all exported directories within the same server 265filesystem be specified on adjacent lines going down the tree. 266You cannot specify a hostname that is also the name of a netgroup. 267Specifying the full domain specification for a hostname can normally 268circumvent the problem. 269.Pp 270Regarding 271.Fl alldirs , 272because NFS mount filehandles are filesystem wide the 273.Fl alldirs 274option applies to exports of the entire filesystem -- even mountpoints 275that are higher up elsewhere in the directory hierarchy. 276Hence if the server has a filesystem 277.Pa /export 278and you wished to export the sub-directory 279.Bd -literal -offset indent 280/export/root/client -alldirs client.foo.com 281.Ed 282.Pp 283you must realize that this also allows mounts to be requested 284against other locations in the 285.Pa /export 286filesystem; thus the host client.foo.com is also permitted to 287mount the directory 288.Pa /export/root/client2 289if it exists. 290