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
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
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