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RESOLVER(5)		  FreeBSD File Formats Manual		   RESOLVER(5)

     resolver -- resolver configuration	file


     The resolver(3) is	a set of routines in the C library which 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 con-
     structed from the domain name.

     The different configuration options are:

     nameserver	 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 multi-
		 ple 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(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.

     search	 Search	list for host-name lookup.  The	search list is nor-
		 mally 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	 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	 Options allows	certain	internal resolver variables to be mod-
		 ified.	 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.

		 no_tld_query  tells the resolver not to attempt to resolve a
			       top level domain	name, that is, a name that
			       contains	no dots.  Use of this option doesn't
			       prevent the resolver from obeying the standard
			       domain and search rules with the	given name.

		 Options may also be specified as a space or tab separated
		 list using the	RES_OPTIONS environment	variable.

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

     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, sepa-
     rated by white space.

     /etc/resolv.conf  The file	resolv.conf resides in /etc.

     gethostbyname(3), resolver(3), hostname(7), named(8)

     Name Server Operations Guide for BIND.

     The resolv.conf file format appeared in 4.3BSD.

FreeBSD	5.2.1		       November	11, 1993		 FreeBSD 5.2.1


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