Repair Your Hard Disk with Disk First Aid

How to launch Disk Utility so you can use its First Aid features on your internal hard disk.

Note: This article is an update of one I wrote way back when Mac OS X 10.3 Panther was released. The instructions here apply to Mac OS X 10.5 Leopard and Mac OS X 10.6 Snow Leopard and will likely apply to most future versions of Mac OS.

Disk Utility IconMac OS X includes a utility called Disk Utility, which can be found in the Utilities folder inside your Applications folder. This program offers features for verifying and repairing permissions and disks, erasing and partitioning volumes, creating and working with disk images, and using RAID.

Disk First Aid

Of this bunch, the First Aid features of Disk Utility are something you might want to check out if you haven’t already. I like to use this feature to clean up file permissions and repair minor directory damage on my hard disks on a regular basis. The trouble is, to use the disk repair features on your startup disk, you can’t start up from that disk or run the software from that disk.

And therein lies the problem: how do you repair your hard disk with Disk Utility if you can’t access the repair feature when you start it from your hard disk?

The answer is on your Mac OS X installation DVD. That disc, which includes the Disk Utility software, can be used to start your computer.

Those of you who have above average knowledge of the installation discs may be scratching your heads. You know that when you start a computer with a Mac OS X installation disc, the Installer application automatically runs. When you use the Installer’s Quit Installer command, the Finder does not appear. Instead, the installer tells you it will restart your computer. So how do you launch Disk Utility?

I’ll tell you.

First of all, you know how to restart your computer from a bootable DVD, right? Insert the DVD and then do one of the following:

  • Use the Startup Disk pane of the System Preferences application to identify the disc as your startup disk.
  • Restart your computer with the Option key held down, select the DVD when the startup disk icons appear, and press Return.
  • Restart your computer with the C key held down.

Wait for your computer to restart from the DVD. Then:

  1. In the first dialog that appears, select your language and click the forward arrow button.
  2. Wait while the installer prepares the installation. Don’t worry; it’s not changing anything on your hard disk.
  3. When the menu bar appears, choose Utilities > Disk Utility.

Disk Utility opens. You can then use its First Air features on your internal hard disk.

When you’re finished:

  1. Choose Disk Utility > Quit Disk Utility or press Command-Q to quit.
  2. When the installer appears, choose Utilities > Startup Disk.
  3. When Startup Disk appears, select your hard disk icon and click Restart.
  4. Click Restart in the confirmation dialog that appears.

Your computer restarts from your hard disk.

It’s in the Book!

Snow Leopard Book CoverYou can find more information about hard disks and using Disk Utility with Mac OS X 10.6 Snow Leopard in Mac OS X 10.6 Snow Leopard: Visual QuickStart Guide.:

  • Storage Media is covered in Chapter 6, pages 97-126.
  • Mac OS Utilities is covered in Chapter 24, pages 569-594.

How to Resolve Startup Issues and Perform Disk Maintenance with Disk Utility and fsck

Another technical note from Apple Support.

Over the past 18 years I’ve been using a Mac — is it that long already? — I’ve had more than one experience when my Mac just wouldn’t start. On two occasions, it was due to a hard disk gone bad — every computer user’s nightmare (are you backing up your important stuff?). On other occasions, it was screwed up but repairable directory files and permissions.

Your Mac comes with tools to help you resolve startup issues. And, in most cases, they really do work. But an important part of keeping your computer running reliably is maintenance — that means running diagnostic/repairs software on it regularly.

From Resolve startup issues and perform disk maintenance with Disk Utility and fsck on Apple Support:

If your computer won’t start up normally, you may need to use a disk repair utility to fix the issue. Mac OS X includes two utilities for this…Disk Utility and fsck. You can also use these even when your computer starts just fine but you want to check the disk for possible file system issues.

The article includes step-by-step instructions for using these two Apple-provided utilities to keep your computer running smoothly.