resolver, resolv.conf - host-address resolver configuration file
This file controls the behavior of then resolver(3N) routines in the C
library. It is read by these routines the first time they are invoked by
The file is designed to be human readable and contains a list of keywords
with values that provide various types of resolver information. The
keyword and value must appear on a single line, and the keyword (for
example, nameserver) must start the line. The value follows the keyword,
separated by white space.
This file is not necessary if there is a name server running on the local
machine and the hostname contains the domain name. It is necessary,
however, if the system administrator wants to override the default
ordering of the host lookup services.
Internet address (in dot notation) of a name server that the
resolver should query. Up to three of these lines can be
specified; 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.) When
specifying a nameserver entry for the local machine, use the
address 0 instead of the localhost address of 127.1.
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
hostname returned by gethostname(2); the domain part is taken to
be everything after the first `.'. Finally, if the hostname
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 can be
changed by listing the desired domain search path following the
search keyword with spaces or tabs separating the names. Most
resolver queries are attempted using each component of the
search path in turn until a match is found. This process can be
slow and generates a lot of network traffic if the servers for
the listed domains are not local. Queries time out if no server
is available for one of the domains.
The first item in the list becomes the default domain name; the
remaining items are the other domains to search after the
The domain and search keywords are mutually exclusive. If more than one
instance of these keywords is present, only the first instance is used.
List of preferred networks. The sortlist keyword is followed by a
list of network addresses. On each lookup the address list is
sorted according to the list of addresses. If multiple addresses
match for a single subnet they are presented in the order returned
from the server. The format of the items of the list is a dotted
quad with an optional slash '/' and netmask.
e.g. sortlist 184.108.40.206/255.255.240.0 220.127.116.11
A list of resolver options. Currently the only supported option is
ndots which specifies how many dots need to be in a name for the
resolver to attempt to lookup the name as a fully qualified name if
the name does not contain a trailing dot. It is followed by a colon
':' and a number. The default is ndots:1.
The hostresorder keyword is now ignored. Resolve order for gethostbyname
and gethostbyaddr is now done in the nsswitch.conf file.
In previous IRIX releases, the resolv.conf file was in the /usr/etc
directory. In order for pre-IRIX5 binaries that use BIND to work
correctly, a symbolic link from /etc/resolv.conf must be made to the old
named(1M), gethostbyname(3N), resolver(3N), hostname(5).
IRIX Admin: Networking and Mail
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