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12.4. Using rndc
BIND includes a utility called
rndc which allows command line administration of the named daemon from the localhost or from a remote host.
In order to prevent unauthorized access to the
named daemon, BIND uses a shared secret key authentication method to grant privileges to hosts. This means an identical key must be present in both /etc/named.conf and the rndc configuration file, /etc/rndc.conf.
12.4.1. Configuring /etc/named.conf
In order for
rndc to connect to a named service, there must a controls statement in the BIND server's /etc/named.conf file.
The
controls statement, shown in the following example, allows rndc to connect from the localhost.
controls {
inet 127.0.0.1 allow { localhost; } keys { <key-name>; };
};
This statement tells
named to listen on the default TCP port 953 of the loopback address and allow rndc commands coming from the localhost, if the proper key is given. The <key-name> specifies a name in the key statement within the /etc/named.conf file. The next example illustrates a sample key statement.
key "<key-name>" {
algorithm hmac-md5;
secret "<key-value>";
};
In this case, the <key-value> uses the HMAC-MD5 algorithm. Use the following command to generate keys using the HMAC-MD5 algorithm:
dnssec-keygen -a hmac-md5 -b <bit-length> -n HOST <key-file-name>
A key with at least a 256-bit length is a good idea. The actual key that should be placed in the <key-value> area can be found in the
<key-file-name> file generated by this command.
Warning
Because
/etc/named.conf is world-readable, it is a good idea to place the key statement in a separate file, readable only by root, and then use an include statement to reference it. For example:
include "/etc/rndc.key";
