B. fsck via Safeboot/Repair Disk
Power outages, hard restarts, and system crashes can lead to disk directory corruption, requiring the use fsck/Repair Disk to correct such. fsck/Repair Disk verifies and, if problems are found, corrects issues with the directory on a disk or volume.
The directory is analogous to a combined address book and road map to where data is stored on a disk or volume. A volume, also known as a partition, is section of a physical hard disk which, from the perspective of the operating system, works like a separate disk. All hard disks have one or more volumes or partitions.fsck via Safe Boot
To start up into Safe Mode (to Safe Boot), do this:
1. Be sure your Mac is shut down.
2. Press the power button.
3. Immediately after you hear the startup tone, hold the Shift key. The Shift key should be held as soon as possible after the startup tone, but not before the tone.
4. Release the Shift key when you see the gray Apple icon and the progress indicator (looks like a spinning gear).
5. Let the progress bar finish.
6. To leave Safe Mode, restart the computer normally, without holding any keys during startup.
This procedure invokes what Apple calls a "Safe Boot": and your Mac will report that it has been booted (started up) into Safe Boot mode. During startup in Safe Boot mode your Mac will do a file system check, entirely in the background, with no working status indicated, or report generated, and any problems will automatically be repaired.
During startup in Mac OS X v10.4 or later, you will see "Safe Boot" on the login window, which appears even if you normally log in automatically.
Instead you may prefer to check your hard drive, and repair any problems, by using the method outlined below. The advantage of using the method outlined below is that both a working status indicator, and a report, are generated. The disadvantage is that you will have to have, and start up from, your OS X Installer CD-ROM.Repair Directory Procedure
1. Start from your Mac OS X Install disc: Insert the installation disc, then restart the computer while holding the C key.
2. When your computer finishes starting up from the disc, choose Disk Utility from the Installer menu. (In Mac OS X 10.4 or later, you must select your language first.)
Important: Do not click Continue in the first screen of the Installer. If you do, you must restart from the disc again to access Disk Utility.
3. Click the First Aid tab.
4. Click the disclosure triangle to the left of the hard drive icon to display the names of your hard disk volumes and partitions.
5. Select your Mac OS X volume.
6. Click Repair. Disk Utility checks and repairs the disk.
**Always start up your computer from an Install or Restore disc when using Disk Utility to verify or repair your startup volume. Otherwise, you might see some disk error messages.**