204 lines
6.8 KiB
Groff
204 lines
6.8 KiB
Groff
.\" $NetBSD: resolv.conf.5,v 1.10 1999/01/15 13:04:10 lukem Exp $
|
|
.\"
|
|
.\" Copyright (c) 1986, 1991 The Regents of the University of California.
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 3. All advertising materials mentioning features or use of this software
|
|
.\" must display the following acknowledgement:
|
|
.\" This product includes software developed by the University of
|
|
.\" California, Berkeley and its contributors.
|
|
.\" 4. 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.
|
|
.\"
|
|
.\" @(#)resolver.5 5.12 (Berkeley) 5/10/91
|
|
.\"
|
|
.Dd January 16, 1999
|
|
.Dt RESOLV.CONF 5
|
|
.Os BSD 4
|
|
.Sh NAME
|
|
.Nm resolv.conf
|
|
.Nd resolver configuration file
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm resolv.conf
|
|
file specifies how the
|
|
.Xr resolver 3
|
|
routines in the C library
|
|
(which provide access to the Internet Domain Name System) should operate.
|
|
The resolver configuration file contains information that is read
|
|
by the resolver routines the first time they are invoked by a process.
|
|
The file is designed to be human readable and contains a list of
|
|
keywords with values that provide various types of resolver information.
|
|
.Pp
|
|
On a normally configured system this file should not be necessary.
|
|
The only name server to be queried will be on the local machine,
|
|
the domain name is determined from the host name,
|
|
and the domain search path is constructed from the domain name.
|
|
.Pp
|
|
The different configuration options are:
|
|
.Bl -tag -width nameserver
|
|
.It Sy nameserver
|
|
Internet address (in dot notation) of a name server
|
|
that the resolver should query.
|
|
Up to
|
|
.Dv MAXNS
|
|
(currently 3) name servers may be listed,
|
|
one per keyword.
|
|
If there are multiple servers,
|
|
the resolver library queries them in the order listed.
|
|
If no
|
|
.Sy nameserver
|
|
entries are present,
|
|
the default is to use the name server on the local machine.
|
|
(The algorithm used is to try a name server, and if the query times out,
|
|
try the next, until out of name servers,
|
|
then repeat trying all the name servers
|
|
until a maximum number of retries are made).
|
|
.It Sy domain
|
|
Local domain name.
|
|
Most queries for names within this domain can use short names
|
|
relative to the local domain.
|
|
If no
|
|
.Sy domain
|
|
entry is present, the domain is determined
|
|
from the local host name returned by
|
|
.Xr gethostname 3 ;
|
|
the domain part is taken to be everything after the first `.'.
|
|
Finally, if the host name does not contain a domain part, the root
|
|
domain is assumed.
|
|
.It Sy lookup
|
|
This keyword has been deprecated by the functionality described in
|
|
.Xr nsswitch.conf 5 .
|
|
.Pp
|
|
.It Sy search
|
|
Search list for host-name lookup.
|
|
The search list is normally determined from the local domain name;
|
|
by default, it begins with the local domain name, then successive
|
|
parent domains that have at least two components in their names.
|
|
This may be changed by listing the desired domain search path
|
|
following the
|
|
.Sy search
|
|
keyword with spaces or tabs separating
|
|
the names.
|
|
Most resolver queries will be attempted using each component
|
|
of the search path in turn until a match is found.
|
|
Note that this process may be slow and will generate a lot of network
|
|
traffic if the servers for the listed domains are not local,
|
|
and that queries will time out if no server is available
|
|
for one of the domains.
|
|
.Pp
|
|
The search list is currently limited to six domains
|
|
with a total of 1024 characters.
|
|
.It Sy sortlist
|
|
Sortlist allows addresses returned by gethostbyname to
|
|
be sorted.
|
|
A sortlist is specified by IP address netmask pairs.
|
|
The netmask is optional and defaults to the natural
|
|
netmask of the net.
|
|
The IP address and optional network pairs are seperated by
|
|
slashes.
|
|
Up to 10 pairs may be specified, ie.
|
|
.Pp
|
|
.Sy sortlist 130.155.160.0/255.255.240.0 130.155.0.0
|
|
.It Sy options
|
|
Options allows certain internal resolver variables to be modified.
|
|
The syntax is:
|
|
.Pp
|
|
.Sy options option ...
|
|
.Pp
|
|
where option is one of the following:
|
|
.Bl -tag -width ndots:n
|
|
.It Sy debug
|
|
enable debugging information, by setting RES_DEBUG in _res.options
|
|
(see
|
|
.Xr resolver 3 ).
|
|
.It Sy inet6
|
|
enable support for IPv6 addresses, by setting RES_USE_INET6 in
|
|
_res.options (see
|
|
.Xr resolver 3 ).
|
|
.It Sy ndots:n
|
|
sets a threshold for the number of dots which
|
|
must appear in a name given to res_query (see
|
|
.Xr resolver 3 )
|
|
before an initial absolute query will be made.
|
|
The default for n is 1, meaning that if there are any
|
|
dots in a name, the name will be tried first as an absolute
|
|
name before any search list elements are appended to it.
|
|
.El
|
|
.El
|
|
.Pp
|
|
The
|
|
.Sy domain
|
|
and
|
|
.Sy search
|
|
keywords are mutually exclusive.
|
|
If more than one instance of these keywords is present,
|
|
the last instance will override.
|
|
.Pp
|
|
The
|
|
.Sy search
|
|
keyword of a system's
|
|
.Pa resolv.conf
|
|
file can be overridden on a per-process basis by setting the
|
|
environment variable
|
|
.Ev LOCALDOMAIN
|
|
to a space-separated list of search domains.
|
|
.Pp
|
|
The
|
|
.Sy options
|
|
keyword of a system's
|
|
.Pa resolv.conf
|
|
file can be amended on a per-process basis by setting the
|
|
environment variable
|
|
.Ev RES_OPTIONS
|
|
to a space-separated list of resolver options as explained above.
|
|
.Pp
|
|
The keyword and value must appear on a single line, and the keyword
|
|
(e.g.
|
|
.Sy nameserver )
|
|
must start the line. The value follows
|
|
the keyword, separated by white space.
|
|
.Sh FILES
|
|
.Bl -tag -width /etc/resolv.conf -compact
|
|
.It Pa /etc/resolv.conf
|
|
The file
|
|
.Nm resolv.conf
|
|
resides in
|
|
.Pa /etc .
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr gethostbyname 3 ,
|
|
.Xr resolver 3 ,
|
|
.Xr nsswitch.conf 5 ,
|
|
.Xr hostname 7 ,
|
|
.Xr named 8
|
|
.Rs
|
|
.%T "Name Server Operations Guide for BIND"
|
|
.Re
|
|
.Sh HISTORY
|
|
The
|
|
.Nm resolv.conf
|
|
file format appeared in
|
|
.Bx 4.3 .
|