You can choose how many times to write over the files. When securely erasing a disk or partition, Disk Utility writes over the erased files, so they can never be recovered.

Many commonly available disk recovery apps can easily recover the files. When erasing a disk or partition, Disk Utility does not erase the actual files it erases only the information used to access the files. You can securely erase a disk or partition to make sure the confidential information it contains cannot be recovered. The following is a summary of the Disk Utility help available from the Help menu when running the Disk Utility application: Securely erase a disk in OS X 10.8 or newer A Recovery Disk can also be created on an external hard disk or thumb drive using the Recovery Disk Assistant: All new OS devices come with a built-in Recovery Disk which can be used by restarting and holding down the R key.

To erase your computer’s startup disk, you must start up from another disk, such as an OS X installation disc or from the Recovery Disk. Disk Utility has shipped on all OS X versions in /Applications/Utilities folder. Secure Erase is documented in the Help menu of the Disk Utility application.

Select the checkbox for “Zero all data”.įor a more secure method of erasing of data, you can select the checkbox “8 Way Random Write Format” instead of or in addition to selecting “Zero all data.” This process could take several hours.

Select the volume format from the Volume Format pop-up menu.

Instead, choose Installer > Open Disk Utilities.

When the Installer screen appears, do not click Continue.

Immediately after the startup sound, press and hold the “C” key to start up from CD.

These steps assume you have a Mac OS X 10.2.3 or later CD: Note:This refers to a full Mac OS X 10.2.3 or later CD included with a computer, not to the update-only 10.2.3 CD. To erase a Macintosh hard disk you can boot with a different disk and use the Disk Utility.

How to clean startup disk on macbook