rndc communicates with the name server over a TCP connection, sending commands authenticated with digital signatures. In the current versions of rndc and named(1Mtcp) the only supported encryption algorithm is HMAC-MD5, which uses a shared secret on each end of the connection. This provides TSIG-style authentication for the command request and the name server's response. All commands sent over the channel must be signed by a key_id known to the server.
rndc reads its default configuration file, /etc/inet/rndc.conf to determine how to contact the name server and decide what algorithm and keys is should use. The -c option can be used to specify an alternate configuration file.
server is the name or address of the server which matches a server statement in the configuration file for rndc . If no server is supplied on the command line, the host named by the default-server clause in the option statement of the configuration file will be used.
The -p option can be used to make rndc send commands to TCP port number port# on the system running the name server instead of BIND 9's default control channel port of 953.
The -y option identifies the key_id to use from the configuration file. key_id must be known by named(1Mtcp) with the same algorithm and secret string in order for control message validation to succeed. If no -y option is provided, rndc will first look for a key clause in the server statement of the server being used, or if no server statement is present for that host, then the default-key clause of the options statement. Note that the configuration file for rdnc contains shared secrets which are used to send authenticated control commands to name servers. It should therefore not have general read or write access.
The -M, -m, and -v options provided debugging information and are primarily of interest only to the BIND 9 developers. They might be changed or removed in future releases.
For the complete set of commands supported by rndc, see the BIND 9 Administrator Guide. or run rndc without arguments to see its help message.
There is currently no way to provide the shared secret for a key_id without using the configuration file.
Several error messages could be clearer. For example, trying to connect from an address that is not in the list of acceptable addresses configured into named(1Mtcp) will result in the error message "end of file" when the server unceremoniously closes the connection.