# Time Machine

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## Time Machine

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6.4. Time Machine As the old saying goes, there are two kinds of people: those who have a regular backup system—and those who will.

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## Nội dung Text: Time Machine

2. • A partition of any one of those drives. The hard drive of another Leopard Mac on the network. You must first mount its drive on your screen (Chapter 13). Tip: It's perfectly OK to back up several Macs onto the same external hard drive, as long as it's got enough room. You can also back up onto a hard drive that has other stuff on it, although of course that means you'll have less room for Time Machine backups. In all cases, the backup disk must be bigger than the drive you're backing up (preferably much bigger). Here's what you can't use as the backup disk: • An iPod. • The iDisk. • Your startup drive. • CDs, DVDs, flash drives, or any other kind of removable disk. Note: If Time Machine doesn't recognize the drive you've given it, the drive might not be a standard Mac-formatted hard drive. That's a gotcha that befalls many a Mac fan who buys a new hard drive for backup purposes; many new drives come in Windows format, which Time Machine doesn't recognize.To make a new, empty drive like this ready for Time Machine, open Disk Utility (Section 10.30.9). Click the drive's name, click the Erase tab, choose Mac OS Extended (Journaled) from the Volume Format pop-up menu, and then click Erase. Sure, it sounds like an Apple plot to sell more hard drives. But you'd be surprised at how cheap hard drives are. At this writing, you can buy a 300-gigabyte internal hard drive for under $90, for goodness' sake, or an external 500-gig drive for$125—and hard drive prices-per-gigabyte only go down. The first time the Mac sees your second hard drive, it invites you to use it as Time Machine's backup drive (Figure 6-5, top). That could be the moment you connect an external USB or FireWire drive, or the first time you turn on the Mac after installing an internal drive. If you click Use as Backup Disk, you're taken immediately to the Time Machine pane of System Preferences (Figure 6-6, bottom). It shows that Time Machine is now on, your
3. backup disk has been selected, and the copying process has begun. The Mac copies everything on your hard drive, including Mac OS X itself, all your programs, and everyone's Home folders. Note: Time Machine doesn't use any compression or encoding; it's copying your files exactly as they sit on your hard drive, for maximum safety and recoverability. On the other hand, it does save some space on the backup drive, because it doesn't bother copying cache files, temporary files, and other files you'll never need to restore. Your total involvement has been one click. And that, ladies and gentlemen, is the easiest setup for a backup program in history. Now go away and let the Mac do its thing. The first backup can take a very long time— hours—as the Mac duplicates your entire internal hard drive onto the second drive. The Mac may feel drugged during this time. Figure 6-5. Top: The Mac has just encountered a second hard drive. Time Machine still works if there's other stuff on the drive, but life is simpler if you don't use that drive for anything but Time Machine. The more space Time Machine has to work with, the farther back in time you'll be able to go to recover deleted or mangled files. Bottom: The backup has begun. You know that because you see both a progress message and the symbol that appears next to the backup drive's name in your Sidebar. 6.4.2. How the Backups Work From now on, Time Machine quietly and automatically checks your Mac once per hour. If any file, folder, or setting changes, it gets backed up at the end of the hour. These follow-up backups, of course, take very little time, since Time Machine backs up only what's changed. So, should disaster strike, the only files you can lose are those that you've changed within the last 59 minutes.
4. Tip: And even then, you can force more frequent backups if you want to. Any time you want Time Machine to update its backup before the hour's up, Control-click (or right- click) Time Machine's icon on the Dock. From the shortcut menu, choose Back Up Now.You can pause the backup the same way—if you need to use the backup drive for another quick task, for example. Control-click the Dock icon and then choose Stop Backing Up. (Don't forget to turn the backing-up on again when you're finished.) By the end of the day, you'll have 24 hourly backups on that second disk, all taking up space. So at day's end, Time Machine replaces that huge stash with a single daily backup. You can no longer rewind your system to 3:00 p.m. last Monday, but you can rewind to the way it was at the end of that day. Similarly, after a week, the dailies are replaced by an end-of-week backup; after a month, the weeklies are replaced by a single end-of-the-month backup. Now you can't rewind to October 24, but you can rewind to November 1. (Apple assumes that it won't take you a whole month to notice that your hard drive has crashed.) Tip: You can see these backups, if you want. Open your backup drive, open the Backups.backupdb folder, and open the folder named for your computer. Inside, you'll find a huge list of backup folders, bearing names like 2007-12-22-155831. That's the backup from December 22, 2007 at 15:58 (that is, 3:58 p.m.) and 31 seconds. The point is that Time Machine doesn't just keep one copy of your stuff. It keeps multiple backups. It remembers how things were in every folder—not just yesterday, but last week, last month, and so on. It keeps on making new snapshots of your hard drive until the backup drive is full. At that point, the oldest ones get deleted to make room for new ones. FREQUENTLY ASKED QUESTION The End of Time What happens when my backup drive gets full? Good question. The whole idea of Time Machine is that it preserves multiple backups, so that you can rewind a window or a drive not just to a backup, but to any date in the past. The bigger the hard drive, the farther back those monthly backups are
5. preserved. Eventually, of course, your backup drive runs out of space. At that point, Time Machine notifies you and offers you a choice. You can keep using that drive; Time Machine will begin deleting the oldest backups to make room for newer ones. Or you can install a new Time Machine backup drive. New backups will go on that one; your older backups will still be available on the original drive. If you ever need to retrieve files or folders from the older disk, Control-click (right-click) the Time Machine icon in the Dock; from the shortcut menu, choose Browse Other Time Machine Disks. In the list of disks, choose the older one. Then click the Time Machine icon on the Dock to enter the Restore mode. Tip: Ordinarily, Time Machine alerts you when it has to start deleting old backups. If you'd rather have it just do it without bothering you, open System Preferences; click Time Machine; click Options; and finally turn off "Warn when old backups are deleted." By the way, if a backup is interrupted—if you shut down the Mac, put it to sleep, or take your laptop on the road—no big deal. Time Machine resumes automatically the next time you're home and connected. 6.4.3. Changing Time Machine Settings Time Machine has three faces in Leopard. There's the application itself, which sits in your Applications folder; click it to enter Restore mode. There's its Dock icon; its shortcut menu has a few commands (like Back Up Now) that aren't available anywhere else. And then there's its System Preferences pane, where you adjust its settings (Figure 6-6). To see it, choose System Preferences, and then click Time Machine. Or choose Time Machine Preferences from Time Machine's Dock icon.
6. Tip: If your information is especially important, or if you're especially paranoid, you can rotate among more than one backup hard drive. Keep one offsite so you won't be hosed in case of fire, flood, or burglary. Figure 6-6. Use the big On/Off switch to shut off all Time Machine activity, although it would be hard to imagine why you'd want to risk it. You can click Choose Backup Disk to choose a different hard drive to represent the mirror of your main drive (after the first one is full, for example). 6.4.4. Recovering Lost or Changed Files All right, you've got Time Machine on the job. You sleep easy at night, confident that your life's in order—and your stuff 's backed up. Then, one day, it happens: Your hard drive crashes. Or you can't find a file or folder you know you had. Or you save a document and then wish you could go back to an earlier draft. Some kind of disaster—sunspots, clueless spouse, overtired self—has befallen your files. This is Time Machine's big moment. Start by pinpointing what you're looking for, in one of these two ways: • Open the disk or folder window where the missing or changed item was POWER USERS' CLINIC Declaring Stuff Off-Limits to Time Machine The whole point of Time Machine, of course, is to have a backup of your entire hard drive. That's how most people use it. It's conceivable, though, that you might want to exclude some files or folders from the Time Machine treatment. There are two reasons. First, you might not want certain, ahem, private materials to be part of your