resolv.conf(4) resolv.conf(4)
NAME
resolv.conf - configuration file for resolver routines
SYNOPSIS
/etc/resolv.conf
DESCRIPTION
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
keyword-value pairs that provide various types of resolver informa-
tion.
The different configuration options are:
nameserver address
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 name
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(3N); 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 name
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. 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.
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resolv.conf(4) resolv.conf(4)
sortlist address
sortlist allows addresses returned by gethostbyname(3N) to be
sorted. A sort list 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. Example:
sortlist 130.155.160.0/255.255.240.0 130.155.0.0
options
options allows certain internal resolver variables to be modi-
fied. The syntax is
options option ...
where option is one of the following:
debug Sets RESDEBUG in res.options.
ndots:n Sets a threshold for the number of dots which must
appear in a name given to resquery [see resolver(3N)]
before an initial absolute query will be made. The
default for n is "1", meaning that if there are any
dots in a name, the name will be tried first as an
absolute name before any search list elements are
appended to it.
The domain and search keywords are mutually exclusive. If more than
one instance of these keywords is present, the last instance wins.
The search keyword of a system's resolv.conf file can be overridden on
a per-process basis by setting the environment variable LOCALDOMAIN to
a space-separated list of search domains.
The options keyword of a system's resolv.conf file can be amended on a
per-process basis by setting the environment variable RESOPTIONS to a
space-separated list of resolver options as explained above under
options.
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
hostname(1), named(1M), gethostent(3N), gethostname(3N), resolver(3N).
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