Disk Utility

Overview

Disk Utility allows the user to do a number of Harddrive maintenance tasks as well as data backup and restoration.  While Time Machine provides a much more elegant view to the user of restoring data over time, Disk Utility allows the user to take a single image and save it, which is useful for saving original configurations for longterm archiving, or for using as a static point to return a machine to its network-ready settings.

Secure Erasing Harddrive

Disk Utility has support to sanitize harddrives.   This is especially useful in the university where some systems will migrate between departments during their lifespan in the network.  It is important to ensure you take appropriate measures to pass on a clean system.

By default, Disk Utility erases only the information used to access the files, not the data in the files themselves. Therefore, the erased files can be recovered. If you need to erase a disk so that the files cannot be recovered, you can select security options within the utility to do so (i.e., write zeros over the disk space).

To do this, reboot your computer with the OSX system CD inside the drive.  Hold down the OPTION key while the computer is starting up to manually select the CD as the booted device.

Select your preferred language. You will then see the Welcome to the Mac OS X Installer window.   From the Installer Menu Bar, click Open Disk Utility. You will then see the Disk Utility window.

In the left pane of the Disk Utility window, click the drive you want to erase.

In the right pane of the Disk Utility window, click the Erase tab.

From the Volume Format drop-down menu, select Mac OS Extended (Journaled).

In the Name field, highlight the existing text and type the name the hard drive is to be called after it's formatted.-  Don't Erase Data--- NOT SECURE - This option only rewrites the headers on the disk. Files can be recovered by forensics, disk utilities, and other advanced recovery software.

-  Zero Out Data--- SECURE for most commercial use - There are forensics utilities that in theory could retrieve some data however they are extremely expensive and time consuming and there are no documented cases of this actually taking place.

-  7-Pass Erase--- SECURE for up to Secret - This is considered sufficient by government standards to erase data from a disk. It writes random data over the disk seven times. It may take several hours or more to complete this process.

-  35-Pass Erase--- SECURE for even the theorists - This makes it absolutely impossible to regain any data off the drive. This option takes an extremely long time, possibly more than one day.
Click the radio button in front of the security measure you require.  35-pass is certainly overkill and likely to be a waste of time.  7-pass is certainly sufficient to pass the computer on to another source.

Click "ok" and then erase and confirm your choices.  Disk Utility will then unmoun the volume, partition the drive, and rename the volume to the name you chose above.