Chapter 16. Berkeley Internet Name Domain (BIND)

235

nameservers use only few of them. The following

zone

statements are very basic examples that can

be used in a master slave nameserver relationship.

The following is an example of a

zone

statement for the primary nameserver hosting

domain.com

:

zone "domain.com" IN {

type master;

file "domain.com.zone";

allow update { none; };

};

In the statement, the zone is identified as

domain.com

, the type is set to

master

, and the

named

service is instructed to read the

/var/named/domain.com.zone

file. It also tells

named

not to

allow by any other hosts to update.

A slave server's

zone

statement for

domain.com

looks slightly different form the previous example.

For a slave server, the type is set to

slave

and in place of the

allow update

line is a directive telling

named

the IP address of the master server.

A slave server's zone statement for domain.com may look like this:

zone "domain.com" {

type slave;

file "domain.com.zone";

masters { 192.168.0.1; };

};

This

zone

statement tells

named

on the slave server to look for the master server at the

192.168.0.1

IP address to find information for the

domain.com

zone. The information the slave server receives

from the master server is saved in the

/var/named/domain.com.zone

file.

16.2.2. Zone Files

Zone files, which contain information about a particular namespace, are stored in the

named

working

directory. By default, this is

/var/named

. Each zone file is named according to the

file

option data

in the

zone

statement, usually in a way that relates to the domain in question and identifies the file as

containing zone data, such as

example.com.zone

.

Each zone file may contain directives and resource records. Directives tell the nameserver to do a

certain thing or apply a special setting to the zone. Resource records define the parameters of the

zone, assigning an identity within the zone's namespace to particular systems. Directives are optional,

but resource records are required to provide nameservice to that zone. All directives and resource

records should go on their own lines.

Comments can be placed after semicolon characters (

;

) in zone files.

16.2.2.1. Zone File Directives

Directives are identified by the leading

$

character before the name of the directive and usually placed

at the top of the zone file.

The following directives are the most commonly used:

  $INCLUDE

  Tells

named

to include another zone file in this zone file at the place where the

directive is used. This allows additional zone settings to be stored apart from the main zone file.

  $ORIGIN

  Sets the domain name to be appended to any unqualified records, such as those that

only specify the host and nothing more.