The resolver is a set of routines in the C library (resolver(4)) that provide access to the Internet Domain Name System. 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.
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. For example: keyword value
The file format is as follows: 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 DomainName
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 Domain_Name1 DomainName2 ...
Search list for host-name lookup. Up to six domains (separated by spaces or tabs) with a total of 256 characters can be specified. If no search entry is present, the search list consists of the local domain name.
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.
You can also specify a search list on a per-process basis by specifying the LOCALDOMAIN environment variable. See resolver(4).
The domain and search keywords are mutually exclusive. If more than one instance of these keywords is present, the last instance will override. options ndots:n
Option for hostname lookup. The n specifies the minimum number of dots a name must contain in order for resolver to look up the name as given. If the lookup fails, the search list (if specified) is applied. The range for n is from 0 to 15. If no options entry is present, the minimum number of dots is 1.
You can also specify the number of dots on a per-process basis by using the RES_OPTIONS environment variable. See resolver(4).
Any white space entered after the domain name is not ignored but is interpreted as part of the domain name.
Functions: gethostbyname(3), resolver(4)
Files: hostname(5) delim off