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Traditional DNS Howto - Page 2

Author: taft

How Do I Answer These Queries Now?

That's where BIND comes into play. The people who maintain the BIND code make sure it meets the specifications of the Internet Engineering Task Force and will run on your server. All you have to do is learn how it does what it does.

Named lives on a domain name server and answers queries from resolvers. The application reads its data from a configuration file called named.conf. named.conf gets its information from something we call zone files. Several zone files exist, but one zone file in particular keeps a database of records that supply named with most of its answers.

In Figure 2, named had received a query. It looks to its configuration file named.conf, which looks to the primary zone file and hands off the information requested to the resolver from the outside.



Figure 2 - Answering a query

Some people refer to configuration files as rule files. BIND's configuration files seem like rule files to me. The rules of Domain Name Services require tight compliance. Making and resolving queries follow strict protocols on the Internet as does the interprocess communication within BIND.

Using Named.conf

Let's refer to Figure 2 again and look at the process. You should have BIND installed and running on your server. If not, we will address installation and configuration in one of the next sections.

The named process listens on port 53 of a Linux system. When it receives a query for an address, it looks to the first configuration file about which it knows: named.conf.



Figure 3 - named.conf

The following table depicts a simple named.conf file. If you have seen a file like this and didn't understand it, then let's break it down into its components. Once we do that, we can take the mystery out of it.

options {
     pid-file "/var/run/bind/run/named.pid";
     directory "/etc/bind";
     // query-source address * port 53; };

//
// a master nameserver config
//
zone "." {
     type hint;
     file "db.root";
};

zone "0.0.127.in-addr.arpa" {
     type master;
     file "db.local";
}; 

zone "158.253.70.in-addr.arpa" {
     type master;
     file "pri.158.253.70.in-addr.arpa";
};

zone "centralsoft.org" {
     type master;
     file "pri.centralsoft.org";
};

This file refers to the four other configuration files. The third line down lists the directory containing them all, /etc/bind where they exist.

The options statement defines the default directory for named and the location of the process ID (pid) file. named.pid represents the daemon itself. If you followed any of the Perfect Setup Tutorials, we put it in a chrooted environment.

The zone statement identifies the location of the hints, localhost, zone and reverse zone files.



Figure 4 - Zone files
Traditional DNS Howto - Page 2