Firstboot

in the process of building an image. i use the following command to build : sudo ..path/to/instaUp2Date.py --process catalogfile.catalog now in one of the catalog files, ive included a firstboot script - at the end of the script it destroys itself - using the srm command in the build process, why does this script run, i dont get it, the mac reboots during the build process (cause in the script ive put that in there). how can i stop this script or any others from running when im trying to create an image. thanks in advance