Securely Wipe an iMac or Mac OS X Based System Hard Drive

Read this if you would like to learn how to securely wipe an iMac or later Apple-based hard drives/partitions. This information is useful for clearing out any private data that you may have on your system prior to giving your system to a friend or selling it to someone else...

Note that this process is irreversible, so be absolutely sure that you would like to erase your data.

Steps

  1. Boot an iMac or Apple-based higher system.
  2. Make sure you've backed up all your necessary data to a thumb or external hard drive. This data includes important documents, media, Itunes files, and bookmarks.
  3. Safely remove this thumb or external hard drive so that it is no longer connected to your system.
  4. As a precaution, physically detach all connected disks that you do not wish to wipe. If you leave them attached, they may get accidentally overwritten and you will not be a happy camper.
  5. Insert an OS 10.4 System disk. Use a CD if you have a CD drive or a DVD/CD if you have a DVD drive.
  6. Restart your system. Go to Apple Menu - Restart. Click Restart when prompted.
  7. Your system should boot the CD. If it doesn't, you may need to restart again and hit the C key to boot the disk.
  8. In the localization (languages) dialog, choose an appropriate language for your needs, or choose Use English as the main language.
  9. Wait a few seconds while a Preparing Installation screen displays.
  10. If you have an early-style iMac system, you will get an Alert message that says: Alert - Your computer is not compatible with Mac OS X 10.4. If so, ignore the message for now. Although you can't install 10.4 on this early-style iMac system, you can use the 10.4 System Disk utility to wipe your system clean.
  11. At the top of your screen, click Utilities Menu - Disk Utility.
  12. Wait for the Disk Utility program to start up.
  13. On the left hand pane, highlight the drive and/or partition you'd like to securely erase.
  14. On the right hand pane, click the Erase tab.
  15. On the right hand pane, choose Security Options...
  16. Choose 7-Pass Erase. Choose 35 if you really want to be sure, but that takes much more time and may be overkill.
  17. Click OK.
  18. On the Right Hand Pane, click Erase.
  19. Read the confirmation message and think about it.
  20. If you're sure, go ahead and click Erase.
  21. Wait many hours for the Erase procedure to take place. When it is completed, there are no helpful messages indicating that it's completed successfully.
  22. At the top of the screen, go to the Disk Utility Menu - Quit Disk Utility.
  23. At the top of the screen, go to the Installer Menu - Quit Installer.
  24. Press and hold the power button for a few seconds to restart your system.
  25. As soon as you hear the restart "boing," eject the 10.4 CD/DVD.
  26. Remove the disc and stow it away.
  27. You now have cleared the entire partition(s) and/or drives. Note that if you have cleared the system drive, the system will not boot. This will be your opportunity to install a fresh operating system, if you wish.

Tips

  • The system disk you use must be 10.4 or later. 10.4 or later contains a special version of Disk Utility that securely wipes drives.

Warnings

  • Back up all your important data. Neither I nor this website accept any responsibility for any accidental data loss that you may encounter. Follow these instructions at your own risk.
  • Note that this process is irreversible, so be absolutely sure that you would like to erase your data.

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