RESOLVER(5) MachTen Programmer’s Manual RESOLVER(5)

NAME
resolver - resolver configuration file

SYNOPSIS
resolv.conf

DESCRIPTION
The resolver(3) is a set of routines in the C library which provide ac-
cess 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 con-
structed 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 multi-
ple 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 normal-
ly determined from the local domain name; by default, it be-
gins with the local domain name, then successive parent do-
mains that have at least two components in their names. This
may be changed by listing the desired domain search path fol-
lowing 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 avail-
able 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, separat-
ed by white space.

FILES
/etc/resolv.conf The file resolv.conf resides in /etc.

SEE ALSO
gethostbyname(3), resolver(3), hostname(7), named(8)

Name Server Operations Guide for BIND.

HISTORY
The resolv.conf file format appeared in 4.3BSD.

4th Berkeley Distribution June 5, 1993 2