I am truly amazed by just how good Time Machine is. I wish that an equivalent backup system existed for every other OS. It’s that good.
With that out of the way, here is how I reverted from 10.7 (Lion) back to 10.6 (Snow Leopard) on my MacBook Air using my original Snow Leopard USB recovery drive and my Time Machine backups, which I had used both before and after upgrading to 10.7 back in August:
- Take a clone of the Lion drive using Carbon Copy Cloner just in case I change my mind/had problems.
- Once completed, go to System Preferences -> Startup Drive and select the recently cloned drive, reboot from that to verify that it worked.
- Shut down.
- Plug in the USB recovery media.
- Power up, holding down Option/Alt to boot from the USB key
- Once booted, go to Disk Utilities and wipe the 10.7 drive. (May not be necessary)
- Under Utilities, choose “Restore from Time Machine Backup”
- Plug in my TimeMachine drive and pick the last 10.6.8 Time Machine backup
- Wait. About an hour from a 5400RPM USB drive to the internal SSD
- Reboot. You’re done!
I use dropbox for everything important, so my files were all synced back. If I happened to miss anything, I have the CarbonCopyCloner copy of my Lion drive on another USB drive. Easy.
One other thing to note is that I originally wiped and reinstalled 10.6 and then tried to recover from the Time Machine backup. This failed because I had used the Time Machine drive after upgrading to 10.7. It was then that I rebooted to recovery media and restored using steps 7-10 instead. So, don’t freak out, and yes you can use Time Machine drive with both 10.6 and 10.7 backups to restore.