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Information Technology

MacOS Secure Disk Erase: Apple Disk Utility

Apple/Macintosh Computer Secure Disk Erase:
Apple Disk Utility

Before You Begin

To securely erase the hard disk of your Macintosh computer, you will need:
  • The Macintosh computer with the hard disk to be erased. The computer must be plugged in to power with its mouse and keyboard attached. It also must have a CD or DVD drive attached, either internally or externally. The computer should be set up in a place where it can sit undisturbed for several hours while the secure erasure is performed.
  • A Mac OS X Installer CD or DVD, version 10.3 or later (secure erase options are not availabe on earlier versions). This can be the disc that came with the computer, a disc from a different Macintosh computer or a generic Mac OS X installer disc.

Secure Erasing with Disk Utility

Once the computer is set up and you have a Mac OS X Installer CD or DVD, follow these instructions:

  1. Turn on the computer. Depending on the model of the Mac, the power button can be on the front or back of the computer.

  2. Insert the Mac OS X Installer CD or DVD. If your installer has multiple CDs, insert Disc 1.

  3. Restart the computer and hold down the C* key. This will instruct the Mac to boot to the Installer CD/DVD instead of the hard disk you are going to erase.
    * If the Mac does not boot to the Installer disc by holding down the C key, restart again and hold down the Option key. When prompted with the choice of bootable volumes, select the CD as your boot device.

  4. Select your language of choice.

  5. At the "Welcome to the Mac OS X Installer" screen, click the Utilities menu and choose Disk Utility.

  6. Select the hard disk you want to erase from the list in the left panel. For most computers, there will only be one hard disk present.

  7. Click the Erase category button on the top of the right panel.

  8. Click the Security Option button.

  9. Select the level of security** you need for the hard disk:

    Don't Erase Data — this is NOT SECURE. Do not select this option for secure erasure of the hard disk.

    Zero Out Data — this will perform a minimally secure erasure in the least amount of time possible.

    7-Pass Erase — this will perform a moderately secure erase, but takes longer to complete.

    35-Pass Erase — this will perform a highly secure erase and takes a significant amount of time to complete.

    ** For more information on how these secure erase options differ, see Apple's documentation, About Disk Utility's secure erase options.

    Click OK once selected.

  10. Click Erase. Do not click "Erase Free Space" as this will not remove any data from the hard disk.

  11. At the confirmation window, click Erase to start the erasure process. Click Cancel if you do not want to erase the selected disk, or if want to choose a different level of security before erasing.

  12. A progress bar will appear in the lower right corner of the Disk Utility window with an estimated time for the erase process to complete. Again, this may be several hours, depending on the level of security you selected.

  13. When erasure is finished, click the Disk Utility menu at the top, and choose Quit Disk Utility.

  14. To quit the Installer, click the Installer menu at the top, and choose Quit Installer.

  15. To retreive your Installer CD/DVD, click the Restart button, then click and hold the mouse button through the restart process until the CD is ejected.

  16. Fill out and affix a Clean Media Label to the computer to indicate its hard disk has been securely erased.
The hard disk should now be erased and the computer ready for recycling.

Last modified February 27 2007 01:46 PM

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