Linux Network Administrator Guide, Second Edition

directory. The Linux file system standard suggests this should be /var/named.

primary

This option takes a domain name and filename as an argument, declaring the local server authoritative for the named domain. As a primary server, named loads the zone information from the given master file.

There will always be at least one primary entry in every boot file used for reverse mapping of network 127.0.0.0, which is the local loopback network.

secondary

This statement takes a domain name, an address list, and a filename as an argument. It declares the local server a secondary master server for the specified domain.

A secondary server holds authoritative data on the domain, too, but it doesn't gather it from files; instead, it tries to download it from the primary server. The IP address of at least one primary server thus must be given to named in the address list. The local server contacts each of them in turn until it successfully transfers the zone database, which is then stored in the backup file given as the third argument. If none of the primary servers responds, the zone data is retrieved from the backup file instead.

named then attempts to refresh the zone data at regular intervals. This process is explained later in connection with the SOA resource record type.

cache

This option takes a domain name and filename as arguments. This file contains the root server hints, which is a list of records pointing to the root name servers. Only NS and A records will be recognized. The domain should be the root domain name, a simple period (.).

This information is absolutely crucial to named; if the cache statement does not occur in the boot file, named will not develop a local cache at all. This situation/lack of development will severely degrade performance and increase network load if the next server queried is not on the local net. Moreover, named will not be able to reach any root name servers, and thus won't resolve any addresses except those it is authoritative for. An exception from this rule involves forwarding servers (see the forwarders option that follows).

forwarders

This statement takes a whitespace-separated list of addresses as an argument. The IP addresses in this list specify a list of name servers that named may query if it fails to resolve a query from its local cache. They are tried in order until one of them responds to the query. Typically, you would use the name server of your network provider or another well-known server as a forwarder.

slave

This statement makes the name server a slave server. It never performs recursive queries itself, but only forwards them to servers specified in the forwarders statement.

There are two options that we will not describe here: sortlist and domain. Two other directives may also be used inside these database files: $INCLUDE and $ORIGIN. Since they are rarely needed, we will not describe them here, either.

The BIND 8 host.conf File

BIND Version 8 introduced a range of new features, and with these came a new configuration file syntax. The named.boot, with its simple single line statements, was replaced by the named.conf file, with a syntax like that of gated and resembling C source syntax.

The new syntax is more complex, but fortunately a tool has been provided that automates conversion from the old syntax to the new syntax. In the BIND 8 source package, a perl program called named-bootconf.pl is provided that will read your existing named.boot file from stdin and convert it into the equivalent named.conf format on stdout. To use it, you must have the perl interpreter installed.

You should use the script somewhat like this:

# cd /etc
# named-bootconf.pl ‹named.boot ›named.conf

The script then produces a named.conf that looks like that shown in Example 6.9. We've cleaned out a few of the helpful comments the script includes to help show the almost direct relationship between the old and the new syntax.

Example 6.9: The BIND 8 equivalent named.conf File for vlager

//
// /etc/named.boot file for vlager.vbrew.com
options {
 directory '/var/named';
};
zone '.' {
 type hint;
 file 'named.ca';
};
zone 'vbrew.com' {
 type master;
 file 'named.hosts';
};
zone '0.0.127.in-addr.arpa' {
 type master;
 file 'named.local';
};
zone '16.172.in-addr.arpa' {
 type master;
 file 'named.rev';
};

If you take a close look, you will see that each of the one-line statements in named.boot has been converted into a C-like statement enclosed within {} characters in the named.conf file.

The comments, which in the named.boot file were indicated by a semicolon (;), are now indicated by two forward slashes (//).

The directory statement has been translated into an options paragraph with a directory clause.

The cache and primary statements have been converted into zone paragraphs with type clauses of hint and master, respectively.

The zone files do not need to be modified in any way; their syntax remains unchanged.

The new configuration syntax allows for many new options that we haven't covered here. If you'd like information on the new options, the best source of information is the documentation supplied with the BIND