Information Technology Reference
Restore the Data, Not the Application
I can't tell you how many times I've heard someone say, “I've lost
my data from Application X, so I want to restore the application
from my backups. How do I do that?” I always reply that restoring
the application is the wrong thing to do.
Nearly all applications—even those, like Address Book, iCal, and
iPhoto, that aren't based on documents—store their data separately
from the application . If data is missing or crashes are occurring,
chances are virtually nil that the application itself is broken, and
restoring it won't bring back your data. Instead, figure out where
the application stores its data (a quick Google search can often help)
and restore those files. If that doesn't work, try restoring the app's
preference file(s) too.
Use Your Bootable Duplicate
In some situations it's clear that your problem is worse than a few
missing files. If your computer won't start up—it gets stuck at a blue
or gray screen or displays a flashing question mark icon—turn next
to your bootable duplicate. Also use your duplicate if many files seem
to be missing or damaged, applications won't launch, you're unable
to start the computer in Recovery mode, or your Mac exhibits other
similar system-wide misbehavior. Follow these steps:
1. Attach the drive containing your bootable duplicate. (Remember,
it must be directly attached to your computer—you can't boot from
a duplicate over a network.)
2. If your computer is already running, restart it; if not, turn it on. As
soon as you hear the startup chime, press and hold the Option key.
3. When your screen shows the volumes available for booting your
Mac, use the arrow keys to select your duplicate and press Return.
Your Mac should boot from the duplicate—but this may take
considerably longer than booting from your regular startup disk.
Once your Mac finishes booting, you can work from your duplicate
if you want. But if possible, check your internal drive and repair it.