xref: /csrg-svn/share/man/man5/resolver.5 (revision 61610)
1*61610Sbostic.\" Copyright (c) 1986, 1991, 1993
2*61610Sbostic.\"	The Regents of the University of California.  All rights reserved.
325718Skjd.\"
449647Scael.\" %sccs.include.redist.roff%
528206Sbloom.\"
6*61610Sbostic.\"     @(#)resolver.5	8.1 (Berkeley) 06/05/93
736741Sbostic.\"
849647Scael.Dd
949647Scael.Dt RESOLVER 5
1049647Scael.Os BSD 4
1149647Scael.Sh NAME
1249647Scael.Nm resolver
1349647Scael.Nd resolver configuration file
1449647Scael.Sh SYNOPSIS
1549647Scael.Nm resolv.conf
1649647Scael.Sh DESCRIPTION
1739709SkarelsThe
1849647Scael.Xr resolver 3
1949647Scaelis a set of routines in the C library
2049647Scaelwhich provide access to the Internet Domain Name System.
2125718SkjdThe resolver configuration file contains information that is read
2228206Sbloomby the resolver routines the first time they are invoked by a process.
2325718SkjdThe file is designed to be human readable and contains a list of
2439709Skarelskeywords with values that provide various types of resolver information.
2549647Scael.Pp
2628206SbloomOn a normally configured system this file should not be necessary.
2739709SkarelsThe only name server to be queried will be on the local machine,
2839709Skarelsthe domain name is determined from the host name,
2939709Skarelsand the domain search path is constructed from the domain name.
3049647Scael.Pp
3125718SkjdThe different configuration options are:
3249647Scael.Bl -tag -width nameserver
3349647Scael.It Sy nameserver
3439709SkarelsInternet address (in dot notation) of a name server
3539709Skarelsthat the resolver should query.
3649647ScaelUp to
3749647Scael.Dv MAXNS
3849647Scael(currently 3) name servers may be listed,
3939709Skarelsone per keyword.
4039709SkarelsIf there are multiple servers,
4139709Skarelsthe resolver library queries them in the order listed.
4249647ScaelIf no
4349647Scael.Sy nameserver
4449647Scaelentries are present,
4528206Sbloomthe default is to use the name server on the local machine.
4626927Skjd(The algorithm used is to try a name server, and if the query times out,
4728206Sbloomtry the next, until out of name servers,
4828206Sbloomthen repeat trying all the name servers
4926927Skjduntil a maximum number of retries are made).
5049647Scael.It Sy domain
5139709SkarelsLocal domain name.
5239709SkarelsMost queries for names within this domain can use short names
5339709Skarelsrelative to the local domain.
5449647ScaelIf no
5549647Scael.Sy domain
5649647Scaelentry is present, the domain is determined
5739709Skarelsfrom the local host name returned by
5849647Scael.Xr gethostname 2 ;
5939709Skarelsthe domain part is taken to be everything after the first `.'.
6028206SbloomFinally, if the host name does not contain a domain part, the root
6128206Sbloomdomain is assumed.
6249647Scael.It Sy search
6339709SkarelsSearch list for host-name lookup.
6439709SkarelsThe search list is normally determined from the local domain name;
6539709Skarelsby default, it begins with the local domain name, then successive
6639709Skarelsparent domains that have at least two components in their names.
6739709SkarelsThis may be changed by listing the desired domain search path
6849647Scaelfollowing the
6949647Scael.Sy search
7049647Scaelkeyword with spaces or tabs separating
7139709Skarelsthe names.
7239709SkarelsMost resolver queries will be attempted using each component
7339709Skarelsof the search path in turn until a match is found.
7439709SkarelsNote that this process may be slow and will generate a lot of network
7539709Skarelstraffic if the servers for the listed domains are not local,
7639709Skarelsand that queries will time out if no server is available
7739709Skarelsfor one of the domains.
7849647Scael.Pp
7939715SkarelsThe search list is currently limited to six domains
8039715Skarelswith a total of 256 characters.
8149647Scael.El
8249647Scael.Pp
8349647ScaelThe
8449647Scael.Sy domain
8549647Scaeland
8649647Scael.Sy search
8749647Scaelkeywords are mutually exclusive.
8839709SkarelsIf more than one instance of these keywords is present,
8939709Skarelsthe last instance will override.
9049647Scael.Pp
9139709SkarelsThe keyword and value must appear on a single line, and the keyword
9249647Scael(e.g.
9349647Scael.Sy nameserver )
9449647Scaelmust start the line.  The value follows
9526927Skjdthe keyword, separated by white space.
9649647Scael.Sh FILES
9749647Scael.Bl -tag -width /etc/resolv.conf -compact
9849647Scael.It Pa /etc/resolv.conf
9949647ScaelThe file
10049647Scael.Nm resolv.conf
10149647Scaelresides in
10249647Scael.Pa /etc .
10349647Scael.El
10449647Scael.Sh SEE ALSO
10549647Scael.Xr gethostbyname 3 ,
10649647Scael.Xr resolver 3 ,
10749647Scael.Xr hostname 7 ,
10849647Scael.Xr named 8
10949647Scael.Rs
11049647Scael.%T "Name Server Operations Guide for BIND"
11149647Scael.Re
11249647Scael.Sh HISTORY
11349647ScaelThe
11449647Scael.Nm resolv.conf
11549647Scaelfile format appeared in
11649647Scael.Bx 4.3 .
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