Downgrade from Lion to Snow Leopard using Time Machine Backups

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:

  1. Take a clone of the Lion drive using Carbon Copy Cloner just in case I change my mind/had problems.
  2. Once completed, go to System Preferences -> Startup Drive and select the recently cloned drive, reboot from that to verify that it worked.
  3. Shut down.
  4. Plug in the USB recovery media.
  5. Power up, holding down Option/Alt to boot from the USB key
  6. Once booted, go to Disk Utilities and wipe the 10.7 drive.  (May not be necessary)
  7. Under Utilities, choose “Restore from Time Machine Backup”
  8. Plug in my TimeMachine drive and pick the last 10.6.8 Time Machine backup
  9. Wait.  About an hour from a 5400RPM USB drive to the internal SSD
  10. 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.


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