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resolv.conf(4)						       resolv.conf(4)

  resolv.conf -	Resolver configuration file




  The resolver is a set	of routines in the C library (resolver(4)) that	pro-
  vide 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	read-
  able and contains a list of keywords with values that	provide	various	types
  of resolver information.

  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. For	example:

       keyword value

  The file format is as	follows:

       nameserver Address

  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 DomainName

  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 . (dot).
  Finally, if the host name does not contain a domain part, the	root domain
  is assumed.

       search Domain_Name1 DomainName2 ...

  Search list for host-name lookup.  Up	to six domains (separated by spaces
  or tabs) with	a total	of 256 characters can be specified.  If	no search
  entry	is present, the	search list consists of	the local domain name.

  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.

  You can also specify a search	list on	a per-process basis by specifying the
  LOCALDOMAIN environment variable. See	resolver(4).

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

       options allow_special all | { \char }

  Option for defining valid characters in hostnames.  Specify all to disable
  hostname checking (allow all characters) or define a set of valid charac-
  ters by using	the { \char } syntax, where char is the	character you want to
  allow.  For example, you can allow the semicolon, underscore,	and colon
  characters by	using {	\; \_ \: }.

  Disabling hostname checking altogether is not	recommended.  By default, the
  allow_special	option is not set and strict hostname checking is enforced.

       options ndots:n

  Option for hostname lookup.  The n specifies the minimum number of dots a
  name must contain in order for resolver to look up the name as given.	 If
  the lookup fails, the	search list (if	specified) is applied. The range for
  n is from 0 to 15.  If no options entry is present, the minimum number of
  dots is 1.

  You can also specify the number of dots on a per-process basis by using the
  RES_OPTIONS environment variable. See	resolver(4).


  Any white space entered after	the domain name	is not ignored but is inter-
  preted as part of the	domain name.


  Commands: named(8)

  Functions:  gethostbyname(3),	resolver(4)

  Files: hostname(5)