Take Control of Backing Up Your Mac, 5th Edition

Create and Use a Duplicate

By long habit, I’ve used the term duplicate as a shortened form of “bootable duplicate,” since the whole point of a duplicate was that you could boot from it. Now, however, considering the numerous reasons one might have a duplicate that’s not bootable, I’m broadening my use of the term to include non-bootable duplicates (which, when speaking of startup disks, include only the read/write Data volume). This chapter covers both types. We begin with the bootable variety, and then (in Create a Data-Only Duplicate) talk about the non-bootable sort.

To review: Bootable duplicates stored on an external SSD let you get back to work quickly if your internal storage fails, give you a useful troubleshooting tool, and make upgrading ...