/etc/rc.cdrom is the rc file used during installation. A modifiedversion is available so that new drivers (i.e. released after 3.3 shipped) can be placed in an install image and installed on systems during a Net Install. This will keep the system from needing to ask for the driver floppy when it reboots during the installation. Also, if the new serial and serial mouse drivers are present, it will modify the Instance0.table to use them.