Today, Software Update popped up and offered me to upgrade the OS to 10.4.8.
Usually I’m turning down such offers as I don’t want to reboot my system in mid-day, but it felt like a good time to do it none the less. This is why I accepted.
After the installation, the update asked me to reboot which I accepted.
What came afterwards was as scary as it was ironic: The system rebooted into Windows XP.
But not worries: The 10.4.8 update isn’t a windows installation in disguise: The Windows installation that greeted me was the one I have on a second partition – mostly to play WoW (which I don’t any more).
A quick reboot showed me even more trouble: Whenever my MacBook tried to boot from the MacOS partition, it showed the folder-with-question-mark icon for a few seconds and then the EFI BIOS emulation kicked in and booted from the MBR, which is why I was seeing Windows on my screen.
Now, I’d gladly explain here what has gone wrong and how I fixed it, but as I was in a state of panic, so I have not exactly documented my fix and as I tried many steps at once without getting confirmation if the step has fixed the problem, I don’t even know what was wrong (which certainly doesn’t stop me from guessing).
I booted from the MacBook DVD and first selected disk utility in the tools menu and let it check the disk for errors (none found as I have expected) and then let it repair permissions (tons of errors found, but I doubt this was the problem).
Then I quit the disk utility and launched terminal.
Beside the fact that I had some trouble actually entering commands (how do I set the keyboard layout in that pre-install-terminal?), I quickly went to /System/Libary, deleted the Extensions cache (Extensions.kextcache), went to /System/Library/Exentsions and removed all Extensions installed by Parallels (which I suspected being responsible for the problem).
I think the list was vmmain.kext, helper.kext, Pvsnet.kext and hypervisor.kext. You have to remove them with rm -r as they are bundles (directories)
After that, I rebooted the system and the question-mark-on-a-folder disappeared and the updating process completed.
I can’t tell you how scared I was: My OS X installation is tweaked to oblivion and I’d really, really hate to lose all the stuff. Don’t mind the data – it’s configuration files and utilities and of course fink.
As I have not tried to reboot after completing each of the steps above, I’m unable to say what actually caused the problem. I doubt it was Parallels though as I’m currently running 10.4.8 and Parallels (which I had to reinstall of course). I also doubt it was the permissions issue as wrong permissions are unlikely to cause boot-failure.
So it probably was a corrupted Extension cache. Or the update process not able to cope with the Parallels extensions.
Me being in the dark makes me unable to place blame, so you won’t find any statement about how a more or less forced OS update should never cause a failure like this…
For all I know, this could have happened without the update anyways.
The good news on the other hand is that I’m slowly reaching a state where I am as good at fixing macs as I am good at fixing Windows and Linux. Just don’t tell this to my friends who have macs.