SD! and Safe Boot
 

I wanted to restore from a backup drive, and in the process, repartition/erase the drive to which I would restore. I booted off the backup drive, but I couldn't partition/erase the drive to which I wanted to restore because it wouldn't unmount (something was "in use," though I couldn't figure out what).

If I boot into "Safe Boot" mode, I can unmount the drive. Any reason I can't use SD! in "Safe Boot" mode?

Thank you!

It's likely because an application or driver is referencing the original drive by name. If you want it to stop that, you'll need to rename the backup drive to the same name as the original before starting up from it.

You're saying that if the backup drive (the one FROM which I wish to restore) is renamed the same as the drive TO which I wish to restore) then this won't happen?

How do I make sure I'm cloning in the right direction in SD! if the drives are named the same?

Yes. SD! won't copy to the drive you're running from... and the icons should show you what drive(s) you're dealing with.