Thanks, guys, for the answer. I've got to admit that I'm disappointed. If you have to decide, before the old system goes down, via a series of moves or copies or hard links or whatever, which kernel you're going to use the next time the system comes up, then it doesn't seem all that useful. I guess if I build a kernel that just doesn't work at all, I can always boot the old kernel far enough to get to single user mode where I can remove the dud /unix, put the old one back, and then reboot. That's something. Anyway, if that's the way it is, then that's the way it is :-) Thanks again. Bob