As many of you have already told us, the Dev-Team has released a new version of Redsn0w , namely the 0.9.6b4, capable of doing the jailbreak to devices with iOS 4.2.1 , the latest version of Apple’s mobile operating system released yesterday.
It is important to emphasize that this tool is only for jailbreak and those users who want to unlock their phone will have to wait for the launch of Ultrasn0w, probably this week, so under no circumstances update your iPhone if you want to have any chance soon. Redsn0w 0.9.6b4 also includes the latest version of Cydia, fully operative under iOS 4.2, and as usual it is available for download on Mac (mirror) and Windows (mirror). Dev-Team Blog
Unfortunately, at the moment the exploit used (the same discovered and used by geohot in Limera1n) only allows the use of the Jailbreak untethered (no bother, go) with the iPhone 3G, some older models of the 3GS and the iPhone touch 2G; while for the others, including the iPhone 4 and the iPad, we need to connect the device to a computer every time we turn it off or restart it in order to use the applications that require Jailbreak through the third option of Redsn0w: “Just boot tethered right now.”
1. After downloading the latest version of Redsn0w from the links provided above or from the Dev-Team website itself, we downloaded the iOS 4.2.1 update through iTunes.
2. We update the iPhone, iPod touch or iPad as we would normally do from iTunes.
3. We turn off our device without disconnecting it from the computer.
4. Run Redsn0w and select the iOS 4.2.1 firmware that you will find inside the iTunes iPhone Software Updates Library (or similar, depending on your device) in your user folder. In the case of iPhone 4, the file should be called iPhone3,1_4.2.1_8C148_Restore.ipsw
5. Press next and follow the instructions given to enter the DFU mode (you know, hold the power button for a few seconds, then press and hold the Home button to finally release the power button seconds later).
And that’s it, you have your iOS 4.2.1 with Jailbreak and Cydia ready for modern life.