Device Firmware Update, or DFU mode as it has come to be known as, is something most iDevice users end up encountering at least once every device. For those of you with the new iPhone 4S, you already have the latest iOS 5 running, so why could you possibly need to boot your device into DFU mode? There is a chance that your firmware crashes, leaving your device stuck in a boot loop, or the possibilities of your device not booting up at all are there. With DFU mode, you can force your device to restore to a clean state via iTunes. While this was the just in case approach, if you plan on jailbreaking your iPhone 4S (which should be coming along anytime), you will definitely need to boot your device in DFU mode, as most jailbreak methods and programs require so. More about the risks, and how you can boot your iPhone 4S in DFU mode, after the break!
As iOS 5 continues to evolve, you can be sure updates to the firmware will follow. Not all updates tend to be device friendly at times, and iOS 4 proved that. So, in case you wind up updating the iOS 5 in the future, you may want to revert back to an earlier version, and that, is some tricky business. There is a huge possibility that you may not be able to do that, so you will have to go around the conventional method requiring your device to be in DFU mode.
Booting your device in DFU mode does not harm your system software at all. It is quite safe, in fact, and you can boot out of it and back to your OS in no time. You simply need to hard reset it by pressing the Home and Power button together for like 10 seconds. So, let’s get to booting your iPhone 4S in DFU mode.
- Make sure that the USB cable is plugged into the iPhone 4S and iTunes is running. (The only reason we have iTunes running is that, once the device boots into DFU, iTunes will prompt you with a dialogue box.)
- Now, turn the device off by holding the power button till Slide to Power Off appears on screen. (If you plugged in the cable after turning the device off, it will turn on again.)
- With your device off. press and hold the Power button for 3 seconds.
- Without releasing the Power button, press the Home button and keep both the buttons pressed for 10 more seconds.
- Release the Power button, but keep the Home button pressed for another 10 seconds.
- The device should kick into DFU mode in around the 7th or 8th second, and iTunes will display a prompt as seen below in the screenshot.
The black and totally blank screen is totally normal; there is no need to be alarmed. This was all that it took for you to put your iPhone 4S in DFU mode. We should, however, point it out that the method to boot into DFU is the same across all versions of iPhone, iPod Touch and iPad.