dfu mode v/s recovery modeThe Main difference between the Recovery mode and DFU mode

[khurana_vikas]

The Main difference between the Recovery mode and DFU mode is iBoot. Recovery mode uses iBoot during restoring or upgrading your iPhone while DFU mode bypasses the iBoot so you can downgrade the current firmware because there is no iBoot agent during the DFU mode. About iBoot, iBoot is the bootloader on iPhone OS devices. iBoot acts on restore while [COLOR=blue ! important][COLOR=blue ! important]iPhone[/COLOR][/COLOR] is in Recovery Mode, iBoot makes sure that you are flashing a firmware version greater than or equal to a current one. If you are not, iBoot will not allow the restore to proceed. Because of this, firmware downgrading must be done in DFU mode.This means if you need to restore your iPhone to current version simply put the iPhone in recovery mode and [COLOR=blue ! important][COLOR=blue ! important]iTunes[/COLOR][/COLOR] takes care of the rest but if you need to downgrade your current firmware to lower one you need to put your iPhone in DFU mode. For example you can’t downgrade Firmware 3.0 to Firmware 2.2.1 without entering in to DFU Mode.


Recovery Mode : Recovery Mode is a state of iBoot that is used during standard upgrades and restores. As iBoot is active, it does not allow you to downgrade your device’s software. Also, unless it is ‘pwned,’ it will not allow custom firmware to be flashed.
DFU Mode : DFU Mode is a special mode where the device can still interface with iTunes, yet it does not load the iBoot. The screen will appear totally black in DFU mode, so you can’t guess whether the device is in DFU or powered down from simply looking at the screen. Because iBoot and the OS are not loaded this exploit makes us able to downgrade your iPhone firmware or upgrade with a custom firmware created by Pwnage tool.
How to put your iPhone in recovery mode :

1. Turn the device completely off and disconnect it from cable/dock.
2. Hold down the home button.
3. While holding down the home button connect to a computer with a cable (easiest) or dock.
4. Keep holding down the home button until you see a connect-to-itunes screen You are now in recovery mode.

To escape Recovery Mode and power the phone off simply hold down power and home buttons for ten seconds.
How to put your iPhone in DFU mode :

1. Connect your iPhone to your computer.
2. Turn iPhone off.
3. Hold power and home together for 10 seconds (exactly).
4. Release power but keep holding home until the computers beeps (observed on a PC) as a USB device is recognized.
5. A few seconds later iTunes should detect your iPhone.
6. If the Restore Logo is present on the screen, you are in Recovery Mode, not DFU.