Verifying and repairing Mac volumes 101

Erik Eckel explains the basics of using Mac's built-in Disk Utility to check the health of disks and repair them when necessary.

Disk issues cause numerous headaches, including slow performance, unplanned downtime or even lost data, for enterprise administrators. This is true whether running Windows or Macs. Unfortunately, most enterprise administrators are more familiar with Windows disk verification and repair processes. Here's a quick primer to get you up to speed using Mac OS X's built-in Disk Utility.

Using Disk Utility

The Mac OS X Disk Utility can verify file and folder permissions, confirm a disk's file system is structured properly and repair many permissions and data structure issues. The utility can even be run on volumes that won't mount properly.

Access the Disk Utility application by opening Finder, selecting Applications, navigating to the Utilities folder, and selecting Disk Utility. The actual application file is Disk stored within the /Applications/Utilities folder.

The Disk Utility console lists connected and recognized hard disks within the left-pane window. Administrators can highlight the respective disk or partition, which then enables several options within the right-pane's First Aid window, including Verify Disk Permissions, Repair Disk Permissions, Verify Disk and Repair Disk.

To confirm the correct permissions are applied to (Apple installed) files and folders, click the Verify Disk Permissions button. Mac OS X will examine the disk or partition, its files' and folders' permissions settings and alert you to any issues that might exist.

To verify the disk's data structures are correct, click the Verify Disk button. A volume's directory database, which the file system uses to note where files and folders are stored on the disk, can be corrupt or errant. The Verify Disk operation will display issues that might exist.

To correct disk permission or disk structure issues, administrators can then click the Repair Disk Permissions or Repair Disk buttons, respectively. Verification, and repair, can take several minutes or longer to complete. Actual verification and repair times will be dependent upon several factors, including disk size, disk health, processor capacity and even available RAM.

While the disk operations are performed, Mac OS X displays a running list of the processes it is performing. These details are displayed within the details window, assuming the Show Details option is checked. Successful operations are displayed in green; errors are displayed in red.

Run Disk Utility from boot DVD when checking system volumes

Administrators seeking to verify and repair system volumes should boot the Mac workstation or server using the Mac OS X Install DVD and selecting Disk Utility from the Utilities menu. Often active system files might prove locked. By running the utility from a boot DVD, administrators receive a higher likelihood that the volume verification and repair operations of system volumes will prove successful.