OS X Mountain Lion Bible

Setting Up for Backup

A backup is—as the name suggests—a reserve force that comes into play when something has gone wrong, typically when something has been lost from your Mac. Usually, you use a backup in two different circumstances. The first is when a file is lost, either because it was accidentally deleted or it became corrupted and is no longer usable. The second—a more serious use—is for disaster recovery. In that case, your Mac is essentially unusable. It may be because of a physical failure of the hard disk or because something critical has happened to the file structure of OS X. Either way, you'll be glad to have a backup on hand.

A backup enables to you to roll back part of your Mac's data to an earlier point—a point where you still had a file that has now been deleted or where the data on your hard disk wasn't corrupted. Fittingly then, Apple offers a comprehensive backup tool called Time Machine, which automatically records changes made to your hard disk and lets you move back in time to recover files and data on your Mac. Furthermore, Time Machine can work directly in many of Apple's key applications.

Note

On MacBooks, OS X automatically saves a copy of recent changes to the startup, which helps OS X recover files if your files hadn't yet been backed up (which could be days or weeks for a MacBook-toting traveler). No user action is required.

Choosing a backup medium

Because the data on your Mac is stored on its hard disk, it makes sense to ensure that your backup ...