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

NAME

       resolv.conf - resolver configuration file

       /etc/resolv.conf

       The  resolver is a set of routines that provide access to the Internet Domain Name System. See resolver(3RESOLV). resolv.conf is a configu-
       ration file that contains the 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.

       The resolv.conf file contains the following configuration directives:

       nameserver	       Specifies  the  IPv4  or  IPv6  Internet  address  of a name server that the resolver is to query. Up to MAXNS name
			       servers may be listed, one per keyword. See <resolv.h>.	If  there  are	multiple  servers,  the  resolver  library
			       queries	them  in  the  order  listed. If no name server entries are present, the resolver library queries the name
			       server on the local machine. The resolver library follows the algorithm to try a name server until the query  times
			       out.  It then tries the name servers that follow, until each query times out. It repeats all the name servers until
			       a maximum number of retries are made.

       domain		       Specifies the 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 sysinfo(2) or from gethostname(3C).
			       (Everything after the first `.' is presumed to be the domain name.) If the host name  does  not	contain  a  domain
			       part, the root domain is assumed. You can use the LOCALDOMAIN environment variable to override the domain name.

       search		       The  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. You can change the default behavior 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. This process may be slow and will
			       generate  a lot of network traffic if the servers for the listed domains are not local. Queries will time out if no
			       server is available for one of the domains.

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

       sortlistaddresslist     Allows addresses returned by the libresolv-internal 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. For example:

			       sortlist 130.155.160.0/255.255.240.0 130.155.0.0

       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 the _res.options field.

			       ndots:n

				   Sets a threshold floor for the number of dots which must appear in a name given to res_query() before  an  ini-
				   tial absolute (as-is) query is performed. See resolver(3RESOLV). The default value for n is 1, which means that
				   if there are any dots in a name, the name is tried first as an absolute name before any  search  list  elements
				   are appended to it.

			       timeout:n
			       retrans:n

				   Sets  the  amount  of  time the resolver will wait for a response from a remote name server before retrying the
				   query by means of a different name server. Measured in seconds, the default is RES_TIMEOUT. See <resolv.h>. The
				   timeout  and  retrans  values are the starting point for an exponential back off procedure where the timeout is
				   doubled for every retransmit attempt.

			       attempts:n
			       retry:n

				   Sets the number of times the resolver will send a query to its name servers before giving up and  returning	an
				   error to the calling application.
				    The default is RES_DFLRETRY. See <resolv.h>.

			       rotate

				   Sets  RES_ROTATE  in  _res.options. The name servers are queried round-robin from among those listed. The query
				   load is spread among all listed servers, rather than having all clients try the first listed server first every
				   time.

			       no-check-names

				   Sets  RES_NOCHECKNAME  in  _res.options. This disables the modern BIND checking of incoming host names and mail
				   names for invalid characters such as underscore (_), non-ASCII, or control characters.

			       inet6

				   Sets RES_USE_INET6 in _res.options. In the Solaris BIND port, this has no  effect  on  gethostbyname(3NSL).	To
				   retrieve IPv6 addresses or IPv4 addresses, use getaddrinfo(3SOCKET) instead of setting inet6.

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

       You can override the search keyword of the system resolv.conf file on a per-process basis by setting the environment  variable  LOCALDOMAIN
       to a space-separated list of search domains.

       You  can amend the options keyword of the system resolv.conf file on a per-process basis by setting the environment variable RES_OPTIONS to
       a space-separated list of resolver options.

       The keyword and value must appear on a single line. Start the line with the keyword, for example, nameserver, followed by the value,  sepa-
       rated by white space.

       /etc/resolv.conf

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard BIND 8.3.3	   |
       +-----------------------------+-----------------------------+

       domainname(1M),	 sysinfo(2),  gethostbyname(3NSL),  getnameinfo(3SOCKET),  getipnodebyname(3SOCKET),  gethostname(3C),	resolver(3RESOLV),
       attributes(5)

       Vixie, Paul, Dunlap, Keven J., Karels, Michael J. Name Server Operations Guide for BIND. Internet Software Consortium, 1996.

								    15 Dec 2004 						    resolv.conf(4)