For the PC equivalent, visit our Running ScanDisk & Defrag guide.

Many common hard drive or OS problems on a Mac can be resolved by running Repair Disk.

Repair Disk

Repair Disk verifies and corrects any bad sectors, corrupted sections or other issues with the directory on a disk or volume. There are two methods to repair a disk—Safe Boot and Disk Utility. Try Safe Boot first.

Safe Boot

  1. Start up in Safe Mode.
  2. After the system has fully started up, restart your computer again normally.

If the computer successfully restarts, you do not need to do any more troubleshooting. If the issue persists, try Disk Utility.

Disk Utility

  1. Insert your Mac OS X Install and restart the computer while holding the C key.
  2. When your computer finishes starting up, choose Disk Utility from the Installer menu.
    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 triangle to the left of the hard drive icon and select your Mac OS X volume.
  5. Click Repair.

If any error messages appear after repairing the disk in the Disk Utility logs, please contact your local Apple Authorized Service Provider for assistance.