| RESOLV.CONF(5) | File Formats Manual | RESOLV.CONF(5) | 
resolv.conf —
resolv.conf file specifies how the
  resolver(3) routines in the C
  library (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 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:
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).The search list is currently limited to six domains with a total of 1024 characters.
sortlist 130.155.160.0/255.255.240.0 130.155.0.0
options option ...
where option is one of the following:
RES_TIMEOUT (see
          ⟨resolv.h⟩).RES_DFLRETRY (see
          ⟨resolv.h⟩).RES_ROTATE in
          _res.options, which causes round robin selection
          of nameservers from among those listed. This has the effect of
          spreading the query load among all listed servers, rather than having
          all clients try the first listed server first every time.RES_NOCHECKNAME in
          _res.options, which disables the modern BIND
          checking of incoming host names and mail names for invalid characters
          such as underscore (‘_’), non-ASCII, or control
          characters.RES_NOCHECKNAME in
          _res.options, which enables the modern BIND
          checking of incoming host names and mail names as described above.
          This is the default.RES_NOTLDQUERY in
          _res.options. This option causes
          res_nsearch() to not attempt to resolve a
          unqualified name as if it were a top level domain (TLD). This option
          can cause problems if the site has “localhost” as a TLD
          rather than having localhost on one or more elements of the search
          list. This option has no effect if neither
          RES_DEFNAMES or
          RES_DNSRCH is set.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, separated by white space.
resolv.conf resides in
      /etc.Paul Vixie, Kevin J. Dunlap, and Michael J. Karels, Name Server Operations Guide for BIND, CSRG,, Department of Electrical Engineering and Computer Sciences,, University of California, Berkeley, Release 4.9.4, http://www.dns.net/dnsrd/docs/bog/bog.html, July 16, 1996.
resolv.conf file format appeared in
  4.3BSD.
| Arril 30, 2021 | NetBSD 10.0 |