Introduction: If your Macintosh computer needs to be reset to factory defaults due to OS errors, or any other reason, you can use a series of commands to accomplish this. Requirements: Local access to a Macintosh computer. Procedure: Boot OS with Power button. Then hold cmd & S. Press enter once get to root prompt. At the prompt, type: mount -uw / rm /var/db/.AppleSetupDone shutdown -h now