Up until now, iOS4.2.1 users could only tether’ jailbreak their iTouch device. A tethered’ jailbreak is a temporary jailbreak and will last only until a reboot. After rebooting, the jailbreak will be lost and the user will again need to jailbreak his iTouch using a PC/Mac. Now, the Chronic Dev. Team has finally released a tethered jailbreak for iTouch devices running iOS4.2.1.
Today, the Chronic Dev. Team tool GreenPois0n was updated to RC5 which will allow users to jailbreak their iPhone 3GS, iPhone 4, iPod Touch 3G/4G and the iPad running on iOS 4.2.1. Unlike Redsn0w, users don’t need SHSH blobs of any previous iOS version to jailbreak. Users, who already have tethered’ jailbroken their iTouch, can directly use GreenPois0n to jailbreak their device.
iPhone 4 owners who are new to the jailbreaking scene and have unlocked their device are recommended to stay away from this jailbreak. They may accidentally update their baseband while updating to iOS 4.2.1 thus losing their unlock. They are suggested to use TinyUmbrella to preserve their baseband whilst upgrading to iOS 4.2.1.
Sadly, at the moment GreenPois0n is only available for Mac. A PC and Windows version is in the pipeline and should be coming soon. Mac owners simply need to download GreenPois0n from here and follow the on-screen instructions.