Domain Name Service (DNS) is an important user service that should be used on every system connected to the Internet. UNIX implementations of DNS are based on the Berkeley Internet Name Domain (BIND) software. BIND provides both a DNS client and a DNS server.
The BIND client issues name queries and is implemented as library routines. It is called the resolver. The resolver is configured in the resolv.conf file. All systems run the resolver.
The BIND server answers name queries and it runs as a daemon. It is called named. named is configured by the named.boot file, which defines where the server gets the domain database information and the type of server being configured. The server types are primary, secondary and caching servers. Because all servers are caching servers, a single configurtaion often encompasses more than one server type.
The original domain database source files are found on the primary server. The domain database file is called a zone file. The zone file is constructed from standard resources records (RR) that are defined in RFCs. The RRs share a common structure and are used to define all DNS database information.
The DNS server can be tested using nslookup. This test tool is included with the BIND release.
In this chapter we have seen how to configure and test domain name service. In the next chapter we configure several other services.