Jailbreaking iOs 4.2.1 With Redsn0w 0.9.6b4

Redsnow 0.9.6b4 was just recently released by iPhone Dev Team and jailbreaking would be the next thing to do. This updated version is based on Geohot's Limera1n bootroom which has already owned all current iOS devices. 

Before we get into the process, let's have a brief description first of what is jailbreaking. It is a process that allows iPad, iPhone and iPod Touch users to gain root access to the command line of the operating system thus removing any limitations imposed upon them by Apple. Having successfully done this, the user could already download themes and extensions which is not available through the App Store via installers such as Cydia as well as installing non Apple operating systems.


Geohot has been successful in making their jailbreaking system in every upgraded iOS that Apple will be releasing. Unlike any jalibreaking process, this one is somewhat difficult because you have to boot it into a "jailbroken state" on every reboot. It is called a tethered jailbreak. It applies to iPhone 3GS (new bootrom), iPhone 4, iPad, iPod touch 2G (MC Model), iPod touch 3G and the iPod touch 4G. Old version iPhone 3GS (old bootrom), iPhone 3G and iPod touch 2G (Non-MC Model) can be jailbroken-untethered using the latest version of Redsnow. Let's wait for another famous hack for the untethered one.


Here is the step by step process on how to do it:


Step 1. Download iOS 4.2.1 for your version of iOS device. 
Step 2. Update/Restore to iOS 4.2.1 firmware using the IPSW file you just downloaded via iTunes 10.1. 
Step 3. Start Redsn0w 0.9.6b4 and point it to iOS 4.2.1 firmware to proceed with the jailbreak. 
Step 4. Now select “Install Cydia” and click “Next”. Optionally (if available), you can also select any other option you like. 
Step 5. Now make sure your device is both OFF and PLUGGED IN to the computer before you click "Next". 
(At this stage you will be presented with a screen where you will have to quickly hold “Power” button and then while holding the “Power” button, you will now have to hold “Home” button too. Now after few seconds release “Power” button but keep holding “Home” button until installation begins.)
Step 6. Sit back and enjoy while redsn0w will do all the rest for you. Once done, your iPhone or iPod touch will restart automatically and you will find it jailbroken on the latest iOS 4.2.1 firmware. 


For For iPhone 4, 3GS (New Bootrom), iPod touch 4G / 3G / 2G, iPad ONLY: 

Step 7. Now from here onwards, whenever you want to do anything related to jailbreak like SSHing into your device, or running Cydia, you must first run your device in the so called “jailbroken state” on every reboot by using “Just boot tethered right now” option in Redsn0w.