How to Repair Permissions on a Mac External Hard Drive

An external hard drive can keep your data backed up and secure.

If you have directories on an external hard drive that give you problems or errors when you are trying to modify, copy or access its files, you may need to repair the permissions on the drive. If your external drive is a boot volume, Mac OS X's Disk Utility diagnostic and repair tool can fix any problems by ensuring that the problem files have the correct permissions.

Things You'll Need

• External boot drive
• FireWire or USB cable

Instructions

1. Plug your external drive into your USB or FireWire port, depending upon the type of connection your drive uses. Wait until the drive mounts to your desktop.

2. Select "Go" from the Finder menu. Scroll down to "Utilities" and locate "Disk Utility" from the folder window that opens. Double-click to launch the program.

3. Locate the name or icon of the external drive attached to your Mac in the left pane of the "Disk Utility" window.

4. Click the "First Aid" tab, then click "Verify Disk Permissions" to begin diagnostics. Wait for "Disk Utility" to read the permissions database on the drive; the progress is indicated by the progress bar at the bottom of the window.

5. Click "Repair Permissions" button when the permissions verification is complete. Wait for "Disk Utility" to repair permissions on the drive. You can also check the progress in the progress bar at the bottom of the window.

6. Click the blue "Eject" button in the toolbar to eject the disk when permissions repair is completed.

Tips & Warnings

• Your external drive must be a boot drive in order for "Repair Permissions" to work.

• Make sure "Time Machine" is set to "Off" when you are repairing permissions on the external disk.

• If "Disk Utility" can not repair your disk permissions, you may need to use a third-party disk repair software.

References

• "MacWorld"; Repairing Permissions: What You Need to Know; Dan Frakes; Aug. 5, 2006