RNDC.CONF(5) BIND 9 RNDC.CONF(5)
NAME
rndc.conf - rndc configuration file
SYNOPSIS
rndc.conf
DESCRIPTION
rndc.conf is the configuration file for rndc, the BIND 9 name server
control utility. This file has a similar structure and syntax to
named.conf. Statements are enclosed in braces and terminated with a
semi-colon. Clauses in the statements are also semi-colon terminated.
The usual comment styles are supported:
C style: /* */
C++ style: // to end of line
Unix style: # to end of line
rndc.conf is much simpler than named.conf. The file uses three state-
ments: an options statement, a server statement, and a key statement.
The options statement contains five clauses. The default-server clause
is followed by the name or address of a name server. This host is used
when no name server is given as an argument to rndc. The default-key
clause is followed by the name of a key, which is identified by a key
statement. If no keyid is provided on the rndc command line, and no key
clause is found in a matching server statement, this default key is used
to authenticate the server's commands and responses. The default-port
clause is followed by the port to connect to on the remote name server.
If no port option is provided on the rndc command line, and no port
clause is found in a matching server statement, this default port is
used to connect. The default-source-address and default-source-ad-
dress-v6 clauses can be used to set the IPv4 and IPv6 source addresses
respectively.
After the server keyword, the server statement includes a string which
is the hostname or address for a name server. The statement has three
possible clauses: key, port, and addresses. The key name must match the
name of a key statement in the file. The port number specifies the port
to connect to. If an addresses clause is supplied, these addresses are
used instead of the server name. Each address can take an optional port.
If an source-address or source-address-v6 is supplied, it is used to
specify the IPv4 and IPv6 source address, respectively.
The key statement begins with an identifying string, the name of the
key. The statement has two clauses. algorithm identifies the authentica-
tion algorithm for rndc to use; currently only HMAC-MD5 (for compatibil-
ity), HMAC-SHA1, HMAC-SHA224, HMAC-SHA256 (default), HMAC-SHA384, and
HMAC-SHA512 are supported. This is followed by a secret clause which
contains the base-64 encoding of the algorithm's authentication key. The
base-64 string is enclosed in double quotes.
There are two common ways to generate the base-64 string for the secret.
The BIND 9 program rndc-confgen can be used to generate a random key, or
the mmencode program, also known as mimencode, can be used to generate a
base-64 string from known input. mmencode does not ship with BIND 9 but
is available on many systems. See the Example section for sample command
lines for each.
EXAMPLE
options {
default-server localhost;
default-key samplekey;
};
server localhost {
key samplekey;
};
server testserver {
key testkey;
addresses { localhost port 5353; };
};
key samplekey {
algorithm hmac-sha256;
secret "6FMfj43Osz4lyb24OIe2iGEz9lf1llJO+lz";
};
key testkey {
algorithm hmac-sha256;
secret "R3HI8P6BKw9ZwXwN3VZKuQ==";
};
In the above example, rndc by default uses the server at localhost
(127.0.0.1) and the key called "samplekey". Commands to the localhost
server use the "samplekey" key, which must also be defined in the
server's configuration file with the same name and secret. The key
statement indicates that "samplekey" uses the HMAC-SHA256 algorithm and
its secret clause contains the base-64 encoding of the HMAC-SHA256 se-
cret enclosed in double quotes.
If rndc -s testserver is used, then rndc connects to the server on lo-
calhost port 5353 using the key "testkey".
To generate a random secret with rndc-confgen:
rndc-confgen
A complete rndc.conf file, including the randomly generated key, is
written to the standard output. Commented-out key and controls state-
ments for named.conf are also printed.
To generate a base-64 secret with mmencode:
echo "known plaintext for a secret" | mmencode
NAME SERVER CONFIGURATION
The name server must be configured to accept rndc connections and to
recognize the key specified in the rndc.conf file, using the controls
statement in named.conf. See the sections on the controls statement in
the BIND 9 Administrator Reference Manual for details.
SEE ALSO
rndc(8), rndc-confgen(8), mmencode(1), BIND 9 Administrator Reference
Manual.
AUTHOR
Internet Systems Consortium
COPYRIGHT
2025, Internet Systems Consortium
9.20.15-1~deb13u1-Debian 2025-10-18 RNDC.CONF(5)
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