ARCHIVED: In the Mac OS X Disk Utility, what is the First Aid function, and when and how should I use it?

Within the Disk Utility program, First Aid is a function for checking and repairing file system errors.

On this page:

• When to use First Aid
• Using First Aid
• Handling problems First Aid cannot repair

When to use First Aid

If your computer is crashing frequently, displaying cryptic error messages, or exhibiting unusual behavior, you can use First Aid as a first step to check for defects and, in many cases, repair them. If, however, your volume has suffered severe corruption, you may need to use other utility programs or repair methods.

Even if you are not getting errors, it is a good idea to run First Aid periodically. This preventive maintenance can help keep small problems from developing into bigger ones.

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Using First Aid

Note: For help with correcting permissions problems rather than file system errors, see ARCHIVED: Using Mac OS X, how do I repair permissions, and what does that do?

To check your startup disk, run First Aid from your software installation DVD:

1. Insert the DVD, and then restart your computer. To force your computer to boot from the DVD, hold down the  c  key.
   
   
2. Follow the instructions on the screen, and when the menu bar appears, from the Utilities (Mac OS X 10.5 and later) or Disk Utilities (Mac OS X 10.4) menu, select Disk Utility.
   
   
3. In the column on the left, select the volume you want to repair, and then on the right, click the First Aid tab. You can select multiple volumes by holding down the Command key while clicking the volumes.
   
   
4. To begin a verification process (a simple check for errors), click Verify Disk. To verify and repair any problems on the selected volume(s), click Repair Disk. You can stop the scan at any time by clicking Stop Verify or Stop Repair.

Results

The results of a verification and/or repair will be posted in the window. Run First Aid repeatedly until you see the following message at the end of the scan, where diskname is the name of your disk:

The volume "diskname" appears to be OK.

Note: Some volumes can be verified but not repaired (e.g., the startup disk, the volume where Disk Utility resides, a write-protected disk such as a DVD-ROM, or a disk that has open files). First Aid will warn you if one of these conditions exists when you select a volume.

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Handling problems First Aid cannot repair

Occasionally, at the end of a scan, a message similar to the following will appear:

"Scan complete. Problems were found, but Disk First Aid cannot repair them."

This indicates that some of your files may be more severely damaged. To repair this damage, you can either back up your disk and reformat, or obtain a more comprehensive disk repair program. Two such programs are DiskWarrior from Alsoft, and TechTool Pro from Micromat Computer Systems.

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