How to Jailbreak Any iOS 4.2.1 Device with Redsn0w 0.9.6b4 (iPhone, iPad or iPod Touch)
Apple's iOS 4.2.1 firmware update was released yesterday to all iPads, iPhones and iPod Touches, with enhanced multitasking features. It was the first significant update for the iPad since its introduction.
And when there's a new firmware update for iOS, there's always a new jailbreak.
RedmondPie has a great how-to on the new jailbreaking process, so check it out. It's pretty simple, but a walkthrough helps make it even easier.
The iPhone Dev Team has just released Redsn0w 0.9.6b4 today which brings first proper jailbreak, with working Cydia and MobileSubstrate for all iOS 4.2.1 devices.
For those of you who don't know, Redsn0w 0.9.6b4 is based on Geohot's Limera1n bootrom exploit which has already pwned all current iOS devices for life. The only problem is that it is a tethered jailbreak, which means you will have to boot it into a "jailbroken state" on every reboot. This so called tethered or semi-tethered jailbreak condition in Redsn0w 0.9.6b4 however only applies to the new devices like: iPhone 3GS (new bootrom), iPhone 4, iPad, iPod touch 2G (MC Model), iPod touch 3G and the iPod touch 4G. Old devices like iPhone 3GS (old bootrom), iPhone 3G and iPod touch 2G (Non-MC Model) can be jailbroken-untethered right now using this latest version of Redsn0w. So until and unless Comex of Spirit and JailbreakMe fame comes up with another untethered hack for iOS 4.2.1, the jailbreak we get for the newer devices will be tethered (or semi-tethered).
NOTE: Those of you who rely on a carrier unlock MUST STAY AWAY from Redsn0w and iOS 4.2.1.
Follow the step by step instructions posted below to jailbreak iOS 4.2.1 with Redsn0w 0.9.6b4:
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.