8.1 BIND: Unix Name ServiceIn Unix, DNS is implemented by the Berkeley Internet Name Domain (BIND) software. BIND is a client/server software system. The client side of BIND is called the resolver. It generates the queries for domain name information and sends them to the server. The DNS server software answers the resolver's queries. The server side of BIND is a daemon called named (pronounced "name" "d"). This chapter covers three basic BIND configuration tasks:
A zone is a piece of the domain namespace over which a name server holds authority. A zone cannot contain a domain that is delegated to another server. Here we use "zone" to refer to the DNS database file, while the term "domain" is used in more general contexts. In this book, a domain is part of the domain hierarchy identified by a domain name. A zone is a collection of domain information contained in a DNS database file. The file that contains the domain information is called a zone file. RFC 1033, the Domain Administrators Operations Guide, defines the basic set of standard records used to construct zone files. Many RFCs propose new DNS records that are not widely implemented. In this chapter and in Appendix C, we stick to the basic resource records that you are most likely to use. We'll use these records to construct the zone files used in this chapter. But how, or even if, you need to construct zone files on your system is controlled by the type of BIND configuration you decide to use. 8.1.1 BIND ConfigurationsBIND configurations are described by the type of service the software is configured to provide. The four levels of service that can be defined in a BIND configuration are resolver-only systems, caching-only servers, master servers, and slave servers. The resolver is the code that asks name servers for domain information. On Unix systems, it is implemented as a library rather than as a separate client program. Some systems, called resolver-only systems, use only the resolver; they don't run a name server. Resolver-only systems are very easy to configure: you just need to set up the /etc/resolv.conf file. The three other BIND configurations all require that the local system run the named server software. They are:
A name server may use any one of these configurations or, as is often the case, it may combine elements of more than one type of configuration. However, all systems run the resolver, so let's begin by examining the configuration of the client side of the DNS software. |