Mac® Security Bible

8.4. Creating Bootable Duplicates

In addition to the versioned backups you can get with Time Machine or other comparable programs, a complete backup plan should include bootable duplicates, which can enable you to get back to work almost instantly in the event of a serious disk problem.

8.4.1. What's a bootable duplicate?

As I said at the beginning of this chapter, a bootable duplicate is a copy of your entire startup disk, created in such a way that you can boot your Mac from it. Back in the days of Mac OS 9 and earlier, you could create a bootable disk simply by dragging your System Folder from your startup disk to another disk and then opening and closing the copied folder to bless it, or get the system to recognize it as valid. However, those days are long gone. If you were to drag all the visible files from your Mac OS X startup disk to another disk, you'd miss all the crucial invisible files that make up the Unix core of the operating system. And even if you did manage to copy those invisible files, they'd almost certainly have their ownership and permissions altered during the copy process in such a way that the end result would no longer be a bootable system. Add to that a few special maintenance tasks (comparable to blessing a System Folder in Mac OS 9), and you have an operation that's too complex and error-prone to attempt by hand.

Fortunately, numerous backup programs know just what to do and can put all the right things in the right places and in the right way. I ...