RESOLVER(5) File Formats Manual RESOLVER(5)
NAME
resolver - resolver configuration file
SYNOPSIS
/etc/resolv.conf
DESCRIPTION
The resolver is a set of routines in the C library (resolv(3)) that provide access to the Internet Domain Name System. The resolver con-
figuration 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:
nameserver
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(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 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 gen-
erate 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.
FILES
/etc/resolv.conf
SEE ALSO
gethostbyname(3N), resolver(3), hostname(7), named(8)
Name Server Operations Guide for BIND
4th Berkeley Distribution December 14, 1989 RESOLVER(5)