Provided by: bind9_9.20.11-1ubuntu3_amd64 
NAME
rndc.conf - rndc configuration file
SYNOPSIS
rndc.conf
DESCRIPTION
rndc.conf is the configuration file for rndc <#std-iscman-rndc>, the BIND 9 name server control utility.
This file has a similar structure and syntax to named.conf <#std-iscman-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 <#std-iscman-named.conf>. The file uses three statements: 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 <#
std-iscman-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-address-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 authentication algorithm for rndc <#std-iscman-rndc> to use; currently only
HMAC-MD5 (for compatibility), 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
<#std-iscman-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 <#std-iscman-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 secret enclosed in double quotes.
If rndc -s testserver <#cmdoption-rndc-s> is used, then rndc <#std-iscman-rndc> connects to the server on
localhost port 5353 using the key "testkey".
To generate a random secret with rndc-confgen <#std-iscman-rndc-confgen>:
rndc-confgen <#std-iscman-rndc-confgen>
A complete rndc.conf file, including the randomly generated key, is written to the standard output.
Commented-out key and controls statements for named.conf <#std-iscman-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 <#std-iscman-named.conf>. See the sections on
the controls statement in the BIND 9 Administrator Reference Manual for details.
SEE ALSO
rndc(8) <#std-iscman-rndc>, rndc-confgen(8) <#std-iscman-rndc-confgen>, mmencode(1), BIND 9 Administrator
Reference Manual.
Author
Internet Systems Consortium
Copyright
2025, Internet Systems Consortium
9.20.11-1ubuntu3-Ubuntu 2025-07-04 RNDC.CONF(5)