resolv.conf(5) - NetBSD Manual Pages

RESOLV.CONF(5)            NetBSD Programmer's Manual            RESOLV.CONF(5)


NAME

     resolv.conf - resolver configuration file


DESCRIPTION

     The resolv.conf file specifies how the resolver(3) routines in the C li-
     brary (which provide access to the Internet Domain Name System) should
     operate.  The resolver configuration file contains information that is
     read by the resolver routines the first time they are invoked by a pro-
     cess.  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(3); 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.

     lookup      This keyword is now ignored: its function has been superseded
                 by features of nsswitch.conf(5).

     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 1024 characters.

     sortlist    Sortlist allows addresses returned by gethostbyname to be
                 sorted.  A sortlist 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
                 seperated by slashes.  Up to 10 pairs may be specified, ie.

                 sortlist 130.155.160.0/255.255.240.0 130.155.0.0

     options     Options allows certain internal resolver variables to be mod-
                 ified.  The syntax is:

                 options option ...

                 where option is one of the following:

                 debug    enable debugging information, by setting RES_DEBUG
                          in _res.options (see resolver(3)).

                 inet6    enable support for IPv6 addresses, by setting
                          RES_USE_INET6 in _res.options (see resolver(3)).

                 ndots:n  sets a threshold for the number of dots which must
                          appear in a name given to res_query (see
                          resolver(3)) 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 el-
                          ements 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 will override.

     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 RES_OPTIONS to a
     space-separated list of resolver options as explained above.

     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), nsswitch.conf(5), hostname(7), named(8)

     Name Server Operations Guide for BIND.


HISTORY

     The resolv.conf file format appeared in 4.3BSD.

NetBSD 1.4                     January 16, 1999                              2