Chapter 20. The Domain Name System

Contents

20.1. DNS Terminology
20.2. Configuration with YaST
20.3. Starting the Name Server BIND
20.4. The Configuration File /etc/named.conf
20.5. Zone Files
20.6. Dynamic Update of Zone Data
20.7. Secure Transactions
20.8. DNS Security
20.9. For More Information

Abstract

DNS (domain name system) is needed to resolve the domain names and hostnames into IP addresses. In this way, the IP address 192.168.0.0 is assigned to the hostname earth, for example. Before setting up your own name server, read the general information about DNS in Section 18.3, “Name Resolution”. The following configuration examples refer to BIND.


20.1. DNS Terminology

Zone

The domain namespace is divided into regions called zones. For instance, if you have opensuse.org, you have the opensuse section, or zone, of the org domain.

DNS server

The DNS server is a server that maintains the name and IP information for a domain. You can have a primary DNS server for master zone, a secondary server for slave zone, or a slave server without any zones for caching.

Master zone DNS server

The master zone includes all hosts from your network and a DNS server master zone stores up-to-date records for all the hosts in your domain.

Slave zone DNS server

A slave zone is a copy of the master zone. The slave zone DNS server obtains its zone data with zone transfer operations from its master server. The slave zone DNS server responds authoritatively for the zone as long as it has valid (not expired) zone data. If the slave cannot obtain a new copy of the zone data, it stops responding for the zone.

Forwarder

Forwarders are DNS servers to which your DNS server should send queries it cannot answer.

Record

The record is information about name and IP address. Supported records and their syntax are described in BIND documentation. Some special records are:

NS record

An NS record tells name servers which machines are in charge of a given domain zone.

MX record

The MX (mail exchange) records describe the machines to contact for directing mail across the Internet.

SOA record

SOA (Start of Authority) record is the first record in a zone file. The SOA record is used when using DNS to synchronize data between multiple computers.