A device firmware update (DFU) restore can be used to restore a Mac computer to factory settings. To perform a DFU restore, connect the Mac to a Mac or PC computer and perform the process using Finder, Apple Devices, or iTunes, depending on the computer used. For more information, see How to revive or restore Mac firmware from the Apple Support website.
Note:
Keep the following in mind about the DFU restore process:
The DFU restore process updates your computer to the newest available OS version.
You can still DFU restore a computer that has the "Disable Connecting with Computers" restriction enabled.
You may need to power off the computer before starting the DFU process.