25 Aug 2005
mac is bac
so after a day (and night) of backing up and copying things over the ultra slow 100Mbps ethernet (400Mbps Firewire is the way to go), it turns out that the road to recovering from an uncurable kernel panic on booting was extremely easy -- in the mac sort of way.
so the problem is that the kernel or some of its modules were corrupted during the last security update. i'm not quite sure how that happened, but it happened. i tried a couple of ways of recovering, such as copying a fresh copy from a known working 10.4.2 machine. that didn't work due to something about unable to find drivers for PowerBook64. then i tried moving all third party kernel extensions (apple terminology for kernel modules) away and nuking the cache, that didn't work either. then i started removing the kernel extension that it was panicking on -- nah, made it even worse.
so i booted it up on firewire target disk mode, plugged it into another mac and then proceeded to copy my 50G home directory to my external firewire drive. this wasn't really done because i was going to nuke my data, but i was going to try the mac os x install option : archive and install
turns out that this is a great way to recover from a corrupted kernel. it takes note of all the files that it knows how to manage, backs them up in a separate directory (which you can delete later) and installs the new files in their place. it keeps all the network and user settings (user home directories and i suppose some things in /etc or the netinfo databases.)
so it took me about a day to move 50G of stuff around to make space for the backups (using xtar and samba) and around 1 hour to do a complete recovery from a non-booting mac to the original mac os x setup i had 3 days ago! pretty impressive.
although i'm still annoyed that the kernel got corrupted when i installed the system update. dunno what happened there.
You can reply to me about this on Twitter: