You should set your system hostname with the hostname command. This is usually called from /etc/rc or /etc/rc.local; simply search your system rc files to determine where it is invoked. For example, if your (full) hostname is loomer.vpizza.com, edit the appropriate rc file to execute the command:
/bin/hostname loomer.vpizza.com
Note that the hostname executable may not be found in /bin on your system.