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resolver(4)							  resolver(4)

  resolver - resolver configuration file




  The resolver is a set	of routines in the C library that provide access to
  the Internet Domain Name System.  The	resolver configuration file
  (resolv.conf)	contains information that is read by the resolver routines
  the first time they are invoked by a process.	The file is designed to	be
  read by humans and contains a	list of	keywords with values that provide
  various types	of resolver information.

  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 every-
	    thing after	the first dot (.). Finally, if the host	name does not
	    contain a domain part, the root domain is assumed.

  search    Search list	for host name lookup. By default, the search list
	    consists of	the local domain name.	You can	change this system
	    wide by specifying search keyword followed by a list of domain
	    names separated by spaces or tabs, or on a per-process basis by
	    specifying the LOCALDOMAIN environment variable followed by	a
	    list of domain names separated by spaces or	tabs.

	    Most resolver queries will be attempted using each component of
	    the	search path in turn until a match is found.  This process
	    might be slow and 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  Enables the	sorting	of addresses returned by gethostname.  A
	    sortlist comprises pairs of	IP addresses and optional netmasks;
	    each IP address and	optional netmask are separated by a slash
	    character (/).  The	netmask	is optional, and defaults to the
	    current network netmask.  You can specify up to 10 pairs.  For

  options ndots:n
	    Option for host name lookup.  By default, when a host name con-
	    tains one or more dots (.),	resolver looks up the name as given
	    before applying the	search list.  The n specifies the minimum
	    number of dots a name must contain in order	to be looked up	as
	    given before applying the search list.  The	range is from 0	to

	    You	can change the resolver	options	system wide by specifying
	    options keyword followed a list of resolver	options	separated by
	    spaces, or on a per-process	basis by specifying the	RES_OPTIONS
	    environment	variable followed by a list of resolver	options
	    separated by spaces.

  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 (for
  example, nameserver) must start the line.  The value follows the keyword,
  separated by white space.




  Functions: dn_comp(3), dn_expand(3), gethostbyname(3), res_init(3),
  res_mkquery(3), res_query(3),	res_search(3), res_send(3).

  Files: hostname(5).

  Commands: named(8).