On my Mac Pro, SuperDuper! automatically clones the boot drive to an internal disk every morning.
But I don't want the backup disk mounted when SD! is not running.
Topher Kessler on Macfixit has just published a way to do this, involving fairly simple editing of system files in Terminal:
http://reviews.cnet.com/8301-13727_7...&subj=MacFixIt
It seems to work, and SD! was able to mount the volume for a scheduled run.
[Previously I used a login AppleScript and shell scripts to do this, but it was clunky, and delayed user login]