resolver - resolver configuration file



     The resolver is a set of routines  in  the  C  library  (resolv(3))  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).

          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(2);  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 list for host-name  lookup.   The  search  list  is  normally
          determined  from  the  local domain name; by default, it begins with
          the local domain name, then successive parent domains that  have  at
          least two components in their names.  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.

     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,
     separated by white space.


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