Setting Up a BIND Configuration File (DNS and BIND, 4th Edition)

4.3. Setting Up a BIND Configuration File

Now that we've created the zone data files, a name server must be instructed to read each of the files. For BIND, the mechanism for pointing the server to its zone data files is the configuration file. Up to this point, we've been discussing files whose data and format are described in the DNS specifications. The configuration file, though, is specific to BIND and is not defined in the DNS RFCs.

The BIND configuration file syntax changed significantly between Version 4 and Version 8. Mercifully, it didn't change at all between BIND 8 and BIND 9. We'll first show you the BIND 4 syntax, and then the equivalent BIND 8 and 9 syntax. You'll have to check the named [24] manual page to find out which you need to use. If you already have a BIND 4 configuration file, you can convert it to a BIND 8 or 9 configuration file by running the program named-bootconf, which is distributed with the BIND source code. In BIND 8, the program is in src/bin/named-bootconf. In BIND 9, it's in contrib/named-bootconf.

[24]named is pronounced "name-dee" and stands for "name server daemon." BIND is pronounced to rhyme with "kind." Some creative people have noticed the similarities in the names and choose to mispronounce them "bin-dee" and "named" (like "tamed").

In BIND 4, comments in the configuration file are the same as in the zone data files -- they start with a semicolon and stop at the end of the line:

; This is a comment

In BIND 8 and 9, you can use any of three styles of comments: C-style, C++-style, or shell-style:

/* This is a C-style comment */
// This is a C++-style comment
# This is a shell-style comment

Don't use a BIND 4-style comment in a BIND 8 or 9 configuration file -- it won't work. The semicolon ends a configuration statement instead of starting a comment.

Usually, configuration files contain a line indicating the directory in which the zone data files are located. The name server changes its directory to this location before reading the zone data files. This allows the filenames to be specified relative to the current directory instead of as full pathnames. Here's how a BIND 4 directory line looks:

directory /var/named

Here's how a BIND 8 or 9 directory line looks:

options {
        directory "/var/named";
        // Place additional options here.
};

TIP: Only one options statement is allowed in the configuration file, so any additional options mentioned later in this book must be added along with the directory option.

On a primary master server, the configuration file contains one line for each zone data file to be read. For BIND 4, this line comprises three fields -- the word primary (starting in the first column), the domain name of the zone, and the filename:

primary  movie.edu                db.movie.edu
primary  249.249.192.in-addr.arpa db.192.249.249
primary  253.253.192.in-addr.arpa db.192.253.253
primary  0.0.127.in-addr.arpa     db.127.0.0

For BIND 8 or 9, the line starts with the keyword zone followed by the domain name and the class (in stands for Internet). The type master is the same as the BIND 4 primary. The last field is the filename:

zone "movie.edu" in {
      type master;
      file "db.movie";
};

Earlier in this chapter, we mentioned that if we omitted the class field from a resource record, the name server would determine the right class to use from the configuration file. The in in the zone statement sets that class to the Internet class. The in is also the default for a BIND 8 or 9 zone statement, so you can leave out the field entirely for Internet class zones. Since the BIND 4 syntax doesn't have a place to specify the class of a zone, the default is in for BIND 4, too.

Here is the BIND 4 configuration file line to read the root hints file:

cache  .  db.cache

and the equivalent BIND 8 or 9 configuration file line:[25]

[25]Actually, BIND 9 has a built-in hints zone, so you don't need to include a zone statement for the hints zone in named.conf. Including one doesn't hurt, though, and it gives us the willies not to see one in the configuration file, so we include one anyway.

zone "." in {
        type hint;
        file "db.cache";
};

As mentioned earlier, this file is not for general cache data. It contains only the root name server hints.

By default, BIND 4 expects the configuration file to be named /etc/named.boot, but it can be changed with a command-line option. BIND 8 and 9 expect the configuration file to be named /etc/named.conf instead of /etc/named.boot. The zone data files for our example are in the directory /var/named. Which directory you use doesn't really matter. Just avoid putting the directory in the root filesystem if the root filesystem is short on space, and make sure that the filesystem the directory is in is mounted before the name server starts. Here is the complete BIND 4 /etc/named.boot file:

; BIND configuration file

directory /var/named

primary  movie.edu                db.movie.edu
primary  249.249.192.in-addr.arpa db.192.249.249
primary  253.253.192.in-addr.arpa db.192.253.253
primary  0.0.127.in-addr.arpa     db.127.0.0
cache    .                        db.cache

Here is the complete BIND 8 or 9 /etc/named.conf file:

// BIND configuration file

options {
        directory "/var/named";
        // Place additional options here.
};
zone "movie.edu" in {
        type master;
        file "db.movie.edu";
};

zone "249.249.192.in-addr.arpa" in {
        type master;
        file "db.192.249.249";
};

zone "253.253.192.in-addr.arpa" in {
        type master;
        file "db.192.253.253";
};

zone "0.0.127.in-addr.arpa" in {
        type master;
        file "db.127.0.0";
};

zone "." in {
        type hint;
        file "db.cache";

};