Disk Utility’s Repair Disk feature can work with any hard drive connected to your Mac, except the startup disk. If you select the startup disk, the ‘Repair Disk’ button will be grayed out. You will only be able to use the Verify Disk feature, which can examine the drive and determine whether anything is wrong.
Repairing a startup drive with Disk Utility is still possible. To do it, you must boot from another hard drive that has OS X installed, or boot from the OS X installation DVD. Aside from the time required to restart from another hard drive an installation DVD or the Recovery HD, using Disk Utility’s Repair Disk feature otherwise works the same way and takes the same amount of time. If you need to boot from an OS X installation DVD, you’ll find instructions on how to do this on pages 2 and 3 of Installing OS X 10.5 Leopard: Upgrading to OS X 10.5 Leopard.
- Back up your drive first. Even though your drive is having some problems, it’s a good idea to create a new backup of a suspect drive before running Repair Disk. While Repair Disk usually doesn’t cause any new problems, it’s possible for the drive to become unusable after an attempt to repair it. This isn’t Disk Repair’s fault. It’s just that the drive was in such bad shape to begin with that Repair Disk’s attempt to scan and repair it kicked the drive over the edge.
- Launch Disk Utility, located at /Applications/Utilities/.
- Select the ‘First Aid’ tab.
- In the left-hand pane, select the hard drive or volume you wish to run Repair Disk on.
- Place a check mark in the ‘Show details’ box.
- Click the ‘Repair Disk’ button.
- If Disk Utility notes any errors, repeat the Repair Disk process until Disk Utility reports ‘The volume xxx appears to be ok.’