1*49647Scael.\" Copyright (c) 1986, 1991 The Regents of the University of California. 236741Sbostic.\" All rights reserved. 325718Skjd.\" 4*49647Scael.\" %sccs.include.redist.roff% 528206Sbloom.\" 6*49647Scael.\" @(#)resolver.5 5.12 (Berkeley) 05/10/91 736741Sbostic.\" 8*49647Scael.Dd 9*49647Scael.Dt RESOLVER 5 10*49647Scael.Os BSD 4 11*49647Scael.Sh NAME 12*49647Scael.Nm resolver 13*49647Scael.Nd resolver configuration file 14*49647Scael.Sh SYNOPSIS 15*49647Scael.Nm resolv.conf 16*49647Scael.Sh DESCRIPTION 1739709SkarelsThe 18*49647Scael.Xr resolver 3 19*49647Scaelis a set of routines in the C library 20*49647Scaelwhich 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. 25*49647Scael.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. 30*49647Scael.Pp 3125718SkjdThe different configuration options are: 32*49647Scael.Bl -tag -width nameserver 33*49647Scael.It Sy nameserver 3439709SkarelsInternet address (in dot notation) of a name server 3539709Skarelsthat the resolver should query. 36*49647ScaelUp to 37*49647Scael.Dv MAXNS 38*49647Scael(currently 3) name servers may be listed, 3939709Skarelsone per keyword. 4039709SkarelsIf there are multiple servers, 4139709Skarelsthe resolver library queries them in the order listed. 42*49647ScaelIf no 43*49647Scael.Sy nameserver 44*49647Scaelentries 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). 50*49647Scael.It Sy domain 5139709SkarelsLocal domain name. 5239709SkarelsMost queries for names within this domain can use short names 5339709Skarelsrelative to the local domain. 54*49647ScaelIf no 55*49647Scael.Sy domain 56*49647Scaelentry is present, the domain is determined 5739709Skarelsfrom the local host name returned by 58*49647Scael.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. 62*49647Scael.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 68*49647Scaelfollowing the 69*49647Scael.Sy search 70*49647Scaelkeyword 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. 78*49647Scael.Pp 7939715SkarelsThe search list is currently limited to six domains 8039715Skarelswith a total of 256 characters. 81*49647Scael.El 82*49647Scael.Pp 83*49647ScaelThe 84*49647Scael.Sy domain 85*49647Scaeland 86*49647Scael.Sy search 87*49647Scaelkeywords are mutually exclusive. 8839709SkarelsIf more than one instance of these keywords is present, 8939709Skarelsthe last instance will override. 90*49647Scael.Pp 9139709SkarelsThe keyword and value must appear on a single line, and the keyword 92*49647Scael(e.g. 93*49647Scael.Sy nameserver ) 94*49647Scaelmust start the line. The value follows 9526927Skjdthe keyword, separated by white space. 96*49647Scael.Sh FILES 97*49647Scael.Bl -tag -width /etc/resolv.conf -compact 98*49647Scael.It Pa /etc/resolv.conf 99*49647ScaelThe file 100*49647Scael.Nm resolv.conf 101*49647Scaelresides in 102*49647Scael.Pa /etc . 103*49647Scael.El 104*49647Scael.Sh SEE ALSO 105*49647Scael.Xr gethostbyname 3 , 106*49647Scael.Xr resolver 3 , 107*49647Scael.Xr hostname 7 , 108*49647Scael.Xr named 8 109*49647Scael.Rs 110*49647Scael.%T "Name Server Operations Guide for BIND" 111*49647Scael.Re 112*49647Scael.Sh HISTORY 113*49647ScaelThe 114*49647Scael.Nm resolv.conf 115*49647Scaelfile format appeared in 116*49647Scael.Bx 4.3 . 117