Recovery mode and Device Firmware Upgrade are two modes of operation of the iPhone in preparation for flashing. Using any of these modes will result in the complete deletion of all information stored in the device, and BaseBand firmware if it is absent.
Instructions
Step 1
DFU is tougher than Recovery. In this mode, the operating system is not loaded, and the signals sent over the USB connection are purely technical in nature. A characteristic feature of the DFU mode is a completely black or completely white screen of a mobile device. The only indicator of DFU health is when iTunes detects a mobile device as a "Stabilize / Restore Device".
Step 2
Connect your mobile device to your computer using the supplied USB cable. Turn off your iPhone using the standard method, i.e. press and hold the Power button until the Power Off slider appears on the screen. Drag the slider to the right and wait for the device to turn off.
Step 3
Launch the iTunes app on your computer. Press and hold the Power and Home buttons for ten seconds. Release the Power button while continuing to hold the Home button. Wait for the device to be detected by iTunes (ten to fifteen seconds) and release the Home button. Remember that the machine's screen will remain completely black. Take the necessary steps to flash the device.
Step 4
To get the phone out of Device Firmware Upgrade mode, connect your mobile device to your computer using a special USB cable. Press and hold the Power and Home buttons for ten seconds. Release both buttons simultaneously after ten seconds. Press the Power button to boot up the device normally in normal mode.
Step 5
Another method to get your phone out of DFU mode is to press the Power and Home buttons at the same time without connecting the device to your computer. Keep both buttons pressed until the Apple logo appears on the screen of the device. Release both buttons and wait for the standard boot of the device.
