"Before you install the new kernel, make a copy of your original kernel. When things fail you can always copy the original kernel back by booting from a different disk or partition. Either X or 9 will work." (from xnu building for mortals - circa 10.1.1) I am rather speechless. This seems like a rather obsolete suggestion for machines that ship with solely OSX now. Is there no such way to boot from the backup kernel you made from the primary disk?. I only have X, I don't have 9. I also only have one Mac. Do I need to keep the original install cd's on hand whenever I am in the mood to dabble? i wrote a simple script to safely swap out kernel builds that might be mildly helpful. to the best of my knowledge, the script only works on ppc machines -- i am unsure how darwin x86 handles its nvram variables (or more specifically boot-device). if madness ensues and the machine fails to boot, you can zap the pram (command-option-p-r) to restore the default boot-device settings. while i have not managed to mess up my boot driver, do keep in mind what josh said about booting off another partition or cd to restore the driver. kswap: <http://opendarwin.org/~jpm/naughty/darwin/kswap.sh> hope this helps. cheers, jean-pierre _______________________________________________ darwin-kernel mailing list | darwin-kernel@lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.