We told you about Dev-Team’s release of PwnageTool 4.2 yesterday. Here’s the full tutorial to Untethered Jailbreak iOS 4.2.1 using a Mac computer. If you have already jailbroken your iPhone 4 using Greenpois0n then you don’t need to jailbreak again. The advantage of PwnageTool over Greenpois0n is that it preserves your baseband and Ultrasn0w unlock.
This tutorial will show you show how to update iPhone 4 to iOS 4.2.1 without upgrading your baseband. This method will preserve iPhone 4’s baseband at 1.59.00 so you don’t lose your software unlock using Ultrasn0w in case you don’t have a factory unlocked iPhone.