Back Up Your Mac Data with Mountain Lion's Time Machine
Time Machine provides an effortless way to back up everything on your Mac. Time Machine saves backups of your Mac data every hour the past 24 hours, and daily backups for the past month. Beyond that, Time Machine goes weekly, at least until the backup drive is packed to the rafters.
When you have no more room in the backup drive, Time Machine starts deleting old backups, so it's best to get a big extra drive to store what's on your Mac. In Time Machine Preferences, you can choose to be notified after these old backups are removed. If you're using Time Machine to back up a laptop, you can determine whether backups should continue while you are using the machine on battery power.
Set up Time Machine on your Mac
Plug in that new secondary hard drive or SSD, and your Mac asks whether you want to use it for a Time Machine backup. You won't regret saying yes, and that's really all you need to do, unless you want to customize which files are backed up.
Apple sells a wireless companion for your Mac called Time Capsule that works nicely with Time Machine. This backup appliance combines a Wi-Fi base station and secondary hard drive. It comes in 2TB ($299) and 3TB ($499) versions.
The Mac begins dutifully copying everything on the computer, including system files. This first copy job is likely to take a while, especially if your Mac is stuffed with files, so start the first backup right before bed. Subsequent backups are a lot quicker because by then, the Mac copies only what's changed.
Although Time Machine is initially set up for automatic hourly backups, you can arrange an immediate backup. Hold the mouse cursor on the Time Machine icon in the dock. Select Back Up Now on the menu that pops up.
Limit Time Machine backups to select files on your Mac
Most people will choose to back up the full contents of their Mac using Time Machine, but if your secondary hard drive is crammed or you have stuff you want to keep private, you can omit certain items from being copied.
Open Time Machine preferences and click Options. Then click + under the Exclude These Items from Backups window to add the files, folders, and drives that you want to exclude, or just drag said items right onto the same do not back up window.
If you've chosen to encrypt files in FileVault, they remain encrypted as part of your Time Machine backup. If you have a Time Capsule and are running Mountain Lion, you can also store encrypted backups there. So even in Time Machine, you'll need a password to get at Aunt Minnie's pudding recipe. What can possibly be more secure than that?
Recover a damaged or lost Mac file
If you need to go back in time to find an earlier version of a saved file, click the Time Machine dock icon, and your current desktop slides out of view. You and whichever Finder-like window was active or front most at the time you clicked the icon are now floating in space.
If you know that the particular item you're looking for used to reside in a given folder, open that window before embarking on your journey. Or enter its name in the search box in the Finder window.
You can now venture across the sands of time to discover the lost or altered file. Say that you unintentionally wiped out a critical document several weeks ago that you now hope to recover. Use the timeline along the right edge of the screen or the navigational arrows toward the lower right to go back to the time of the deed.
When you click, the windows fly forward or backward for a second or two until landing on the day you chose. If your search-and-rescue mission doesn't immediately uncover the lost file, try typing its name again in the Finder search box.
You are searching for the file on that particular date. When you encounter the wayward file, highlight it and click Restore. It's transported back to the present, with Time Machine conveniently dropping the file in its original location. Click Cancel to return to the present.