How to Secure Erase a Mac SSD / Hard Disk from Recovery Mode
The newest Macs ship with a Recovery partition rather than a separate external reinstall disk, and if you’ve ever rebooted a newer Mac, iMac, MacBook Air, or MacBook Pro with an SSD from the Recovery partition to reformat the drive, you may have noticed that by default the “Security Options” button is greyed out in the Disk Utility options, seemingly preventing a standard “secure” erase procedure. The precise reason for this isn’t entirely clear, though some speculate it’s because writing 1’s and 0’s to an SSD can lead to performance degradation and a reduction in the drives lifespan, and that it persists even in the most recent versions of OS X suggests it’s not just a bug. Nonetheless, many users want the option for secure removal of data from the SSD. The most obvious solution to this problem is to boot the Mac from an external boot drive (here’s how to make one for Mountain Lion), but that isn’t always an option for everyone, but fortunately there is a workaround that lets you perform a secure erase directly from the Recovery partition itself.
This is very much a workaround, as you’ll technically be erasing the drive twice in the process. The first time will not be the secure erase, it’s the second time formatting that will allow you to achieve the desired outcome. For users with an SSD drive, it’s important to note that using the secure formatting options like 7 pass and 35 pass could potentially lead to a reduction in drive life span, or performance degradation, though TRIM is thought to mitigate that risk. Be sure you understand that and are comfortable with that potential before proceeding.
Secure Format an SSD (or the OS X Boot Disk) via Recovery Mode
Though it may be obvious, it’s important to point out and to remember that this process removes all data from the drive, which then becomes unrecoverable due to the highly secure formatting options. Always back up important data before formatting a drive, or else it will be gone forever.
- Reboot the MacBook and hold down the OPTION key, then select the Recovery partition
- At the OS X Utilities menu, choose “Disk Utility”
- Select the hard drives primary partition (usually called Macintosh HD) from the left, then choose the “Erase” tab
- Under “Format” choose “Mac OS Extended (Journaled, Encrypted) – the “Encrypted” part is crucial
- Choose “Erase” and set a password for the encrypted partition, for now choose a simple password that’s easy to remember, then choose “Erase”
- Let the drive erase and turn into an encrypted format, this process can take a while depending on the drive type, size, and speed
- Now select the partition in Disk Utility again, and from the “Erase” tab choose “Mac OS Extended (Journaled)”
- Notice the “Erase Free Space” and “Security Options” buttons are now clickable as expected, choose “Security Options” and select your level of secure erasure, “35-Pass Erase” is by far the most secure but takes 35 times longer because it literally writes over the drives existing data 35 times
- Choose “OK” and let the secure erase proceed, when finished you will have a blank primary partition that has been securely formatted
The Macs hard drive has now been securely erased, entirely from the built-in Recovery partition, and without the need of an external boot drive or disk. At this point you may want to repair the disk since you’re already booted into Recovery, or you can exit out of Disk Utility and re-install a clean version of OS X on the Mac if desired, or do whatever else you want with your newly blank hard drive space.
Note, this does not remove the Recovery partition. You can do that separately if desired, but it is not recommended as you will be unable to restore OS X or boot into Recovery mode once it has been removed, thereby requiring the usage of an external boot disk to install Mac OS X back onto the machine.
Heads up to David for passing along the basis of this trick from MacRumors Forums. We have confirmed this works on a MacBook Air with a solid state drive, but if anyone knows of a better method of secure formatting the SSD drives of Macs or the boot disk by way of Recovery Mode, let us know in the comments!