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named.conf

The configuration file for the named daemon is named.conf, located in the /etc directory. It uses a flexible syntax similar to C programs. The format enables easy configuration of selected zones, enabling features such as access control lists and categorized logging. The named.conf file consists of BIND configuration statements with attached blocks within which specific options are listed. A configuration statement is followed by arguments and a block that is delimited with braces. Within the block are lines of option and feature entries. Each entry is terminated with a semicolon. Comments can use the C, C++, or Shell/Perl syntax: enclosing

/*

*/ , preceding

// , or preceding

# . The following example shows a

zone statement followed by the zone name and a block of options that begin with an opening brace,

{ . Each option entry ends with a semicolon. The entire block ends with a closing brace, also followed by a semicolon. The format for a named.conf entry is shown here, along with the different kinds of comments allowed. Tables 35-5, 35-6, and 35-7 list several commonly used statements and options.

// comments
/* comments */
# comments
statements {
options and features; //comments
};

The following example shows a simple caching server entry:

// a caching only nameserver config
//
zone "." {
type hint;
file "named.ca";
};

zone Statement

The

zone statement is used to specify the domains the name server will service. You enter the keyword

zone , followed by the name of the domain placed within double quotes. Do not place a period at the end of the domain name. In the following example, a period is within the domain name, but not at the end, "mytrek.com"; this differs from the zone file, which requires a period at the end of a complete domain name.

After the zone name, you can specify the class

in , which stands for Internet. You can also leave it out, in which case

in is assumed (there are only a few other esoteric classes that are rarely used). Within the zone block, you can place several options (see Table 34-6 later in this chapter). Two essential options are

type and

file . The

type option is used to specify the zone's type. The

file option is used to specify the name of the zone file to be used for this zone. You can choose from several types of zones: master, slave, stub, forward, and hint. Master specifies that the zone holds master information and is authorized to act on it. A master server was called a primary server in the older 4.x BIND configuration. Slave indicates that the zone needs to update its data periodically from a specified master name server. You use this entry if your name server is operating as a secondary server for another primary (master) DNS server. A stub zone copies only other name server entries, instead of the entire zone. A forward zone directs all queries to name servers specified in a

forwarders statement. A hint zone specifies the set of root name servers used by all Internet DNS servers. You can also specify several options that can override any global options set with the

options statement. Table 34-4 lists the BIND zone types. The following example shows a simple

zone statement for the mytrek.com domain. Its class is Internet (in) and its type is master. The name of its zone file is usually the same as the zone name, in this case, "mytrek.com."

zone "mytrek.com" in {
type master;
file "mytrek.com";
};

Configuration Statements

Other statements, such as

acl ,

server ,

options , and

logging , enable you to configure different features for your name server (see DNSSEC" later in this chapter). The

logging statement is used to configure logging options for the name server, such as the maximum size of the log file and a severity level for messages. Table 34-5 lists the BIND statements. The

sortlists statement lets you specify preferences to be used when a query returns multiple responses. For example, you could give preference to your localhost network or to a private local network such a 192.168.0.0.