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Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" @(#)exports.5 8.3 (Berkeley) 3/29/95 .\" $FreeBSD$ .\" .Dd June 30, 2008 .Dt EXPORTS 5 .Os .Sh NAME .Nm exports .Nd define remote mount points for .Tn NFS mount requests .Sh SYNOPSIS .Nm .Sh DESCRIPTION The .Nm file specifies remote mount points for the .Tn NFS mount protocol per the .Tn NFS server specification; see .%T "Network File System Protocol Specification" , RFC1094, Appendix A and .%T "NFS: Network File System Version 3 Specification" , Appendix I. .Pp Each line in the file (other than comment lines that begin with a #) specifies the mount point(s) and export flags within one local server file system for one or more hosts. A long line may be split over several lines by ending all but the last line with a backslash .Pq Ql \e . A host may be specified only once for each local file system on the server and there may be only one default entry for each server file system that applies to all other hosts. The latter exports the file system to the .Dq world and should be used only when the file system contains public information. .Pp In a mount entry, the first field(s) specify the directory path(s) within a server file system that can be mounted on by the corresponding client(s). There are two forms of this specification. The first is to list all mount points as absolute directory paths separated by whitespace. The second is to specify the pathname of the root of the file system followed by the .Fl alldirs flag; this form allows the host(s) to mount at any point within the file system, including regular files if the .Fl r option is used on .Xr mountd 8 . The pathnames must not have any symbolic links in them and should not have any .Dq Pa \&. or .Dq Pa .. components. Mount points for a file system may appear on multiple lines each with different sets of hosts and export options. .Pp The second component of a line specifies how the file system is to be exported to the host set. The option flags specify whether the file system is exported read-only or read-write and how the client UID is mapped to user credentials on the server. .Pp Export options are specified as follows: .Pp .Sm off .Fl maproot Li = Sy user .Sm on The credential of the specified user is used for remote access by root. The credential includes all the groups to which the user is a member on the local machine (see .Xr id 1 ) . The user may be specified by name or number. .Pp .Sm off .Fl maproot Li = Sy user:group1:group2:... .Sm on The colon separated list is used to specify the precise credential to be used for remote access by root. The elements of the list may be either names or numbers. Note that user: should be used to distinguish a credential containing no groups from a complete credential for that user. .Pp .Sm off .Fl mapall Li = Sy user .Sm on or .Sm off .Fl mapall Li = Sy user:group1:group2:... .Sm on specifies a mapping for all client UIDs (including root) using the same semantics as .Fl maproot . .Pp The option .Fl r is a synonym for .Fl maproot in an effort to be backward compatible with older export file formats. .Pp In the absence of .Fl maproot and .Fl mapall options, remote accesses by root will result in using a credential of -2:-2. All other users will be mapped to their remote credential. If a .Fl maproot option is given, remote access by root will be mapped to that credential instead of -2:-2. If a .Fl mapall option is given, all users (including root) will be mapped to that credential in place of their own. .Pp The .Fl ro option specifies that the file system should be exported read-only (default read/write). The option .Fl o is a synonym for .Fl ro in an effort to be backward compatible with older export file formats. .Pp .Tn WebNFS exports strictly according to the spec (RFC 2054 and RFC 2055) can be done with the .Fl public flag. However, this flag in itself allows r/w access to all files in the file system, not requiring reserved ports and not remapping UIDs. It is only provided to conform to the spec, and should normally not be used. For a .Tn WebNFS export, use the .Fl webnfs flag, which implies .Fl public , .Sm off .Fl mapall No = Sy nobody .Sm on and .Fl ro . Note that only one file system can be .Tn WebNFS exported on a server. .Pp A .Sm off .Fl index No = Pa file .Sm on option can be used to specify a file whose handle will be returned if a directory is looked up using the public filehandle .Pq Tn WebNFS . This is to mimic the behavior of URLs. If no .Fl index option is specified, a directory filehandle will be returned as usual. The .Fl index option only makes sense in combination with the .Fl public or .Fl webnfs flags. .Pp Specifying the .Fl quiet option will inhibit some of the syslog diagnostics for bad lines in .Pa /etc/exports . This can be useful to avoid annoying error messages for known possible problems (see .Sx EXAMPLES below). .Pp The third component of a line specifies the host set to which the line applies. The set may be specified in three ways. The first way is to list the host name(s) separated by white space. (Standard Internet .Dq dot addresses may be used in place of names.) The second way is to specify a .Dq netgroup as defined in the .Pa netgroup file (see .Xr netgroup 5 ) . The third way is to specify an Internet subnetwork using a network and network mask that is defined as the set of all hosts with addresses within the subnetwork. This latter approach requires less overhead within the kernel and is recommended for cases where the export line refers to a large number of clients within an administrative subnet. .Pp The first two cases are specified by simply listing the name(s) separated by whitespace. All names are checked to see if they are .Dq netgroup names first and are assumed to be hostnames otherwise. Using the full domain specification for a hostname can normally circumvent the problem of a host that has the same name as a netgroup. The third case is specified by the flag .Sm off .Fl network Li = Sy netname Op Li / Ar prefixlength .Sm on and optionally .Sm off .Fl mask No = Sy netmask . .Sm on The netmask may be specified either by attaching a .Ar prefixlength to the .Fl network option, or by using a separate .Fl mask option. If the mask is not specified, it will default to the mask for that network class (A, B or C; see .Xr inet 4 ) . See the .Sx EXAMPLES section below. .Pp Scoped IPv6 address must carry scope identifier as documented in .Xr inet6 4 . For example, .Dq Li fe80::%re2/10 is used to specify .Li fe80::/10 on .Li re2 interface. .Pp The .Xr mountd 8 utility can be made to re-read the .Nm file by sending it a hangup signal as follows: .Bd -literal -offset indent /etc/rc.d/mountd reload .Ed .Pp After sending the .Dv SIGHUP , check the .Xr syslogd 8 output to see whether .Xr mountd 8 logged any parsing errors in the .Nm file. .Sh FILES .Bl -tag -width /etc/exports -compact .It Pa /etc/exports the default remote mount-point file .El .Sh EXAMPLES .Bd -literal -offset indent /usr /usr/local -maproot=0:10 friends /usr -maproot=daemon grumpy.cis.uoguelph.ca 131.104.48.16 /usr -ro -mapall=nobody /u -maproot=bin: -network 131.104.48 -mask 255.255.255.0 /a -network 192.168.0/24 /a -network 3ffe:1ce1:1:fe80::/64 /u2 -maproot=root friends /u2 -alldirs -network cis-net -mask cis-mask /cdrom -alldirs,quiet,ro -network 192.168.33.0 -mask 255.255.255.0 .Ed .Pp Given that .Pa /usr , /u , /a and .Pa /u2 are local file system mount points, the above example specifies the following: .Pp The file system rooted at .Pa /usr is exported to hosts .Em friends where friends is specified in the netgroup file with users mapped to their remote credentials and root mapped to UID 0 and group 10. It is exported read-write and the hosts in .Dq friends can mount either .Pa /usr or .Pa /usr/local . It is exported to .Em 131.104.48.16 and .Em grumpy.cis.uoguelph.ca with users mapped to their remote credentials and root mapped to the user and groups associated with .Dq daemon ; it is exported to the rest of the world as read-only with all users mapped to the user and groups associated with .Dq nobody . .Pp The file system rooted at .Pa /u is exported to all hosts on the subnetwork .Em 131.104.48 with root mapped to the UID for .Dq bin and with no group access. .Pp The file system rooted at .Pa /u2 is exported to the hosts in .Dq friends with root mapped to UID and groups associated with .Dq root ; it is exported to all hosts on network .Dq cis-net allowing mounts at any directory within /u2. .Pp The file system rooted at .Pa /a is exported to the network 192.168.0.0, with a netmask of 255.255.255.0. However, the netmask length in the entry for .Pa /a is not specified through a .Fl mask option, but through the .Li / Ns Ar prefix notation. .Pp The file system rooted at .Pa /a is also exported to the IPv6 network .Li 3ffe:1ce1:1:fe80:: address, using the upper 64 bits as the prefix. Note that, unlike with IPv4 network addresses, the specified network address must be complete, and not just contain the upper bits. With IPv6 addresses, the .Fl mask option must not be used. .Pp The file system rooted at .Pa /cdrom will be exported read-only to the entire network 192.168.33.0/24, including all its subdirectories. Since .Pa /cdrom is the conventional mountpoint for a CD-ROM device, this export will fail if no CD-ROM medium is currently mounted there since that line would then attempt to export a subdirectory of the root file system with the .Fl alldirs option which is not allowed. The .Fl quiet option will then suppress the error message for this condition that would normally be syslogged. As soon as an actual CD-ROM is going to be mounted, .Xr mount 8 will notify .Xr mountd 8 about this situation, and the .Pa /cdrom file system will be exported as intended. Note that without using the .Fl alldirs option, the export would always succeed. While there is no CD-ROM medium mounted under .Pa /cdrom , it would export the (normally empty) directory .Pa /cdrom of the root file system instead. .Sh SEE ALSO .Xr netgroup 5 , .Xr mountd 8 , .Xr nfsd 8 , .Xr showmount 8 .Sh BUGS The export options are tied to the local mount points in the kernel and must be non-contradictory for any exported subdirectory of the local server mount point. It is recommended that all exported directories within the same server file system be specified on adjacent lines going down the tree. You cannot specify a hostname that is also the name of a netgroup. Specifying the full domain specification for a hostname can normally circumvent the problem.