autodns-dhcp_ddns is the script that updates the dns data, it also settles the information given dinamically on the dhcp server configuration, so that things become static instead of dynamic. It does this by creating the update instructions for nsupdate and BIND, and writing host entries with the name, MAC and IP addresses on the dhcp configuration. This script is called from autodns-dhcp_cron, and should not be called directly, if the user wants to force any updates, he should call autodns-dhcp_cron and not autodns-dhcp_ddns directly.