Some of you may have experienced the unfortunate kernel panic on boot problem that is occurring on certain Macs after they’ve installed recent software updates. If you haven’t installed the “Thunderbolt Software Update 1.2″ yet it’s best to avoid it completely until a fix comes from Apple. If it’s too late and you’re experiencing crashes on reboot, then you’ll probably want to know the cause of the kernel panics is that recent Thunderbolt Update and we’ve got three different ways to resolve the problem.
Before beginning, there’s some good news and some bad news. The good news is each of these methods will maintain your files, preferences, apps, settings, and customizations. The bad news is that you’ll either have to reinstall OS X (just the operating system), or restore from a Time Machine backup. Regardless of which approach you take, do not install the Thunderbolt update again when the Mac reboots if it’s available in Software Update, wait until a fixed version comes from Apple within a day or two.
Fix #1: Use Internet Recovery
This will redownload and reinstall OS X Lion from the internet, it’s fairly automated once you begin the recovery process.
- Reboot the Mac and hold down Command+R to boot into Recovery Mode
- Select “Re-install OS X” and enter your Apple ID
- Let Internet Recovery do it’s magic
Fix #2: Use Time Machine and Restore from Recent Backup
This is only going to be practical for those who make regular Time Machine backups, if you don’t, you should start doing so now.
- Reboot the Mac and hold down Command+R or Option to enter into Recovery Mode
- From the boot menu choose Time Machine and “Restore”, following the onscreen instructions to select the most recent backup to restore from
Fix #3: Reinstall OS X from a Boot USB or DVD
Assuming you followed our instructions from a while back on how to make a bootable Lion USB drive, you can use this approach:
- Connect the USB drive to the Mac and reboot, holding down the Option key
- Select the Lion boot disk from the boot menu
- Choose “Reinstall OS X” from the options
This method will require you to reinstall general system updates afterwards, because the version of OS X being installed is the same as what’s contained on the USB boot drive. This is probably the least practical approach as a result.
Regardless of the approach you take, do not reinstall the Thunderbolt update. We’re repeating that because if you do reinstall it before it’s fixed by Apple, you will end up in the same kernel panic situation again and that’s no fun. These kind of problems are fairly rare but they can happen, which is why we recommend regularly backing up a Mac with Time Machine as one of the four essential maintenance tips for any Mac OS X machine.
If you need further assistance, jump into the comments or join the lengthy forum thread on Apple Discussion Boards.
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