If you’re one of the lucky folks who have purchased a new Mac, you may be considering selling or donating your old Mac. Before getting rid of your beast, you’ll want to wipe the data from it, and slap on a fresh installation of OS X. Here’s how.
Backup or Clone Your Hard Drive
It’s likely that you have already moved your old Mac’s data to your new machine. However, it’s always a good idea to have a backup around, just in case you find something you missed moving over during the transfer. (Trust me, this ALWAYS happens!)
If you’ve already been using Time Machine to backup your old Mac, you should be good to go. Just be sure not to write over your Time Machine backup when you start backing up your new Mac.
Other backup options include such utilities as SuperDuper or Carbon Copy Cloner. These utilities can clone your Mac’s hard drive to an external hard drive. If needed, you can even boot your Mac from the clone on the external drive.
Deauthorize iTunes
If you used iTunes on your old Mac, remember that Apple’s iTunes only allows a certain number of devices to be authorized with any one iTunes account. Remember to deauthorize your old Mac, so you can easily add your new Mac to the account.
To deauthorize a Mac, simply start iTunes, then click the “Store” menu selection. You’ll see a pull-down menu appear. Click “Deauthorize This Computer.” You will then need to enter your Apple ID information, and then click “Deauthorize.”
Restart Your Mac and Boot Into Recovery Mode
Make sure your Mac is connected to the Internet, (you’ll need an Internet connection to reinstall OS X, unless you have an install disk or USB drive), then restart your Mac by clicking on the Apple in the upper-left hand corner of your Mac’s Desktop. Click “Restart” in the Apple menu.
As your Mac begins to reboot, simultaneously hold down the Command + R keys. Hold these two keys down until the “Recovery Mode” screen loads.
Erase Your Hard Drive
Now, Select “Disk Utility,” and then click on “Continue.” Select your Mac’s Startup Disk in the sidebar on the left, and then click your mouse pointer on the “Erase” tab on the right-hand side of the window.
If you are afraid someone might try to recover your data, click on the “Security Options…” button and select a higher form of security for erasing your data. (Note: This WILL take quite a bit longer than a normal erase.) Click the “Erase…” button and the utility will begin to erase your hard drive.
WARNING: Before formatting, be VERY sure you either have a backup, or are sure that you do not want anything that remains on the hard drive. This will permanently erase your Mac’s hard drive.
When the drive is erased, exit the utility by selecting “Disk Utility,” and then “Quit Disk Utility.”
Install OS X
When you’re back to the main screen, click on “Reinstall OS X” and then select “Install.” This will download and install a fresh copy of OS X on your Mac. Continue the installation until you see the prompt to enter your Apple ID and password. Do NOT enter it! This is the spot where you’ll stop, in order to allow the new owner to enter their login information and complete the setup process for themselves.
By following the above steps, you’ll erase all of your apps and personal information from your old Mac, enabling a fresh start for its new owner.