Together with the ovm_vmmessage utility on the Oracle VM Manager, the Oracle VM Guest Additions form a bi-directional messaging channel between Oracle VM Manager and the guest. More specifically, as part of the Oracle VM Guest Additions, a command line tool called ovmd is installed. It allows first-boot installation configuration, and is capable of sending and receiving messages consisting of key-value pairs just like the ovm_vmmessage utility. As you can see in the help, ovmd has the following command line options:

# ovmd --help
usage: ovmd [options]

options:
-p, --set-param=PARAM   Set param in format: key=value.
-g, --get-param=KEY     Get param value.
-r, --delete-param=KEY  Delete param by key name.
-x, --delete-params     Delete all params.
-l, --list-params       List all params.
-e, --event=EVENT       Inject event.
-s, --script=SCRIPT     Run script.
-d, --debug=LEVEL       Set debug level: 0(DEBUG_OFF), 1(DEBUG_STDERR) or 2(DEBUG_SYSLOG). Default: 2.
-f, --pid-file=FILENAME Set the pathname of the process ID (PID) file.
-t, --time-period=secs  Set the period for daemon mode(default=10 seconds).
-v, --version           Show version number and exit.
-h, --help              Show this help information.