Media Disposal (Mac) - Securely erasing a hard drive in Mac OS X
When disposing of an old computer, you should be mindful of any personal data you may have left behind on the computer. Files containing sensitive information (e.g. tax documents, student grades, etc.) could be accessed by unauthorized people if the hard drive of the computer isn't securely erased. This document explains how to securely erase a hard drive on a Mac OS X computer using Disk Utility, a utility provided by Apple.
Preparing to wipe your hard drive
There are a few things you should do before you securely erase your hard drive.
- Make sure that you have backed up any important files from the computer you are going to erase
- Safely disconnect any USB hard drives or flash drives from the computer you are going to erase to reduce the risk of accidentally erasing those drives
Erasing you hard drive
Once you have prepared your computer by backing up important files and disconnecting any external hard drives or flash drives, you can erase your hard drive using Disk Utility:
- Insert your Mac OS X Install CD/DVD into your drive
- Restart the computer and hold down the C key on your keyboard as soon as the gray loading screen appears. This will boot the computer from CD/DVD.
- Select your preferred language. You will then see the Welcome to Mac OS X Installer screen.
- From the Utilities menu in the top menu bar, select Disk Utility
- Disk Utility will open, as shown below. Click on the hard drive that you want to erase in the left menu. For example, we have selected 'Macintosh HD' which is the default name. The drive you are erasing may be different, so take care on this step.
- Click on the Erase tab, as shown below.
- Click on the Security Options button.
- Select 7-pass Erase and click OK
- Click the Erase button to begin the secure erasure.
- Once this process has begun, you will likely need to wait a few hours for it to complete.
Once this is complete, you can power the computer off and dispose of it as appropriate.