Whether it’s an unresponsive device, an upgrade gone bad, or some other sort of software-based gremlin, sometimes you literally have to force iTunes to recognize and restore your iOS device. Short for Device Firmware Update, DFU mode is a last resort for bringing misbehaving units back to working order—and here’s how to trigger it. To start, you need to have the device plugged into your computer via USB, and then turn it off. Once…
