How to jailbreak iOS 4.2.1

Apple is launching iOS 4.2.1 today, bringing multitasking and icon folders to the iPad, and wireless printing and media streaming to the iPad, iPhone, and iPod touch. But even before Apple was ready to push out the latest version of iOS to the public, hackers figured out how to jailbreak it.

If you update a jailbroken iPhone, iPad, or iPod touch to iOS 4.2.1, you’ll automatically lose the jailbreak functionality. The Cydia store for third party apps that aren’t allowed into the App Store won’t work, and neither will those apps.

But you can use the Redsn0w tool to jailbreak your phone once the OS update is complete.

The hack works with the iPhone 3G and up, as well as second, third, and fourth generation iPod touch models. Just bear in mind, there’s currently no carrier unlock hack for iOS 4.2.1, so if you’ve already unlocked your iPhone to work with a carrier in the US that’s not AT&T, you’re going to want to hold off on upgrading to iOS 4.2.1 until an unlock tool is available.

Right now Cydia isn’t compatible with iOS 4.2.1, but an updated version is on the way.

You can find step by step instructions for jailbreaking iOS 4.2.1 at Redmond Pie.