listing for R
resolver - resolver configuration file
The resolver is a set of routines in the C library that provide access to
the Internet Domain Name System. The resolver configuration file
(resolv.conf) contains information that is read by the resolver routines
the first time they are invoked by a process. The file is designed to be
read by humans and contains a list of keywords with values that provide
various types of resolver information.
The different configuration options are:
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).
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(); the domain part is taken to be everything after the
first dot (.). Finally, if the host name does not contain a domain
part, the root domain is assumed.
Search list for host name lookup. By default, the search list consists
of the local domain name. You can change this system wide by
specifying search keyword followed by a list of domain names separated
by spaces or tabs, or on a per-process basis by specifying the
LOCALDOMAIN environment variable followed by a list of domain names
separated by spaces or tabs.
Most resolver queries will be attempted using each component of the
search path in turn until a match is found. This process might be slow
and 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
Enables the sorting of addresses returned by gethostname. A sortlist
comprises pairs of IP addresses and optional netmasks; each IP address
and optional netmask are separated by a slash character (/). The
netmask is optional, and defaults to the current network netmask. You
can specify up to 10 pairs. For example:
sortlist 22.214.171.124/255.255.240.0 126.96.36.199
Option for host name lookup. By default, when a host name contains one
or more dots (.), resolver looks up the name as given before applying
the search list. The n specifies the minimum number of dots a name
must contain in order to be looked up as given before applying the
search list. The range is from 0 to 15.
You can change the resolver options system wide by specifying options
keyword followed a list of resolver options separated by spaces, or on
a per-process basis by specifying the RES_OPTIONS environment variable
followed by a list of resolver options separated by spaces.
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 (for
example, nameserver) must start the line. The value follows the keyword,
separated by white space.
Functions: dn_comp(3), dn_expand(3), gethostbyname(3), res_init(3),
res_mkquery(3), res_query(3), res_search(3), res_send(3)
listing for R