How to Securely Erase a Mac OS X Hard Disc or Volume

Use Disk Utility to securely erase a disk

Securely erasing a hard disk entails making multiple passes to remove all data written on that disk, so no trace of it remains. One of the most common scenarios in which you would want to securely erase a disk is when you sell or dispose of a computer or hard drive. Securely erasing the disk will permanently remove all of your old data so it cannot be restored.

Things You'll Need

• Mac OS X Disk utility

Instructions

1. 

   In an open Finder window, click on the "Applications" icon in the sidebar. Scroll down to the "Utilities" folder and click to open the folder. Scroll down in the "Utilities" folder and find "Disk Utilities." Double-click "Utilities" to launch the application.

2. 

   In the "Disk Utility" application window, click on the "Erase" button in the top row of radio buttons, then click the "Security Options" button along the bottom of the window to open the "Security Options" preferences.

3. 

   Click the desired "Security Option" button on the "Security Options" preference pane window in "Disk Utility." "Zero Out Data" will preform a "one-pass" erase. This is the least secure option. "7-Pass Erase" will write over the data on your drive seven times. This is the most common secure-erase procedure, and will render virtually unreadable all data that was previously written to the drive. The "35-Pass Erase" option will write over your data on the drive 35 times. This is the most secure erase option; however, it will take hours or days to wipe the data from your drive.

4. 

   Click "OK" in the "Secure Erase" options. The window will close. Now click the "Erase" button in the lower right-hand corner of the "Disk Utility" window. The drive or volume will be erased with your "Secure Erase" options.

Tips & Warnings

• Make sure you back up all of your data. Selecting "Secure Erase" will wipe all data from your drive or volume.