*nix Documentation Project
·  Home
 +   man pages
·  Linux HOWTOs
·  FreeBSD Tips
·  *niX Forums

  man pages->Linux man pages -> resolver (5)              



NAME    [Toc]    [Back]

       resolver - resolver configuration file

SYNOPSIS    [Toc]    [Back]


DESCRIPTION    [Toc]    [Back]

       The  resolver is a set of routines in the C library that provide access
       to the Internet Domain Name System.  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.

       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.

       The different configuration options are:

	      Internet	address  (in  dot  notation) of a name server that the
	      resolver should query.  Up to 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
	      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).

       domain Local  domain  name.   Most queries for names within this domain
	      can use short names relative to the local domain.  If no	domain
	      entry  is  present, the domain is determined from the local host
	      name returned by gethostname(); 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.

       search Search list for host-name lookup.  The search list  is  normally
	      determined  from	the local domain name; by default, it contains
	      only the local domain name.  This may be changed by listing  the
	      desired  domain  search  path  following the 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.

	      The search list is currently limited to six domains with a total
	      of 256 characters.

	      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 separated
	      by slashes. Up to 10 pairs may be specified.

	      e.g. sortlist

	      Options allows certain internal resolver variables to  be  modified.
  The syntax is

	      options option ...

	      where option is one of the following:

	      debug -- sets RES_DEBUG in _res.options.

	      ndots:n  --  sets  a threshold for the number of dots which must
	      appear in a name given to res_query (see 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.

       The domain and search keywords are mutually exclusive.	If  more  than
       one instance of these keywords is present, the last instance wins.

       The  search keyword of a system's resolv.conf file can be overridden on
       a per-process basis by setting the environment variable ``LOCALDOMAIN''
       to a space-separated list of search domains.

       The  options keyword of a system's resolv.conf file can be amended on a
       per-process basis by setting the environment  variable  ``RES_OPTIONS''
       to  a space-separated list of resolver options as explained above under

       The keyword and value must appear on a single  line,  and  the  keyword
       (e.g.  nameserver) must start the line.	The value follows the keyword,
       separated by white space.

FILES    [Toc]    [Back]


SEE ALSO    [Toc]    [Back]

       gethostbyname(3), hostname(7), named(8),
       Name Server Operations Guide for BIND

4th Berkeley Distribution	  1993-11-11			   RESOLVER(5)
[ Back ]
 Similar pages
Name OS Title
resolver IRIX host-address resolver configuration file (DNS/NIS)
amd.conf FreeBSD amd configuration file
apt.conf Linux Configuration file for APT
man.conf OpenBSD configuration file for man(1)
rndc.conf HP-UX rndc configuration file
slp.conf HP-UX Configuration file for SLP Agents
krb5.conf HP-UX Kerberos configuration file
tcpd.conf HP-UX configuration file for tcpd
named.conf HP-UX configuration file for NameDaemon
inetd.conf HP-UX configuration file for inetd
Copyright © 2004-2005 DeniX Solutions SRL
newsletter delivery service