What a Tethered Jailbreak for iOS 4.2.1 Means
An explanation of what a tethered jailbreak is and what it means for those looking to jailbreak iOS 4.2.1, courtesy of the iPhone Dev-Team.
● If youre on an iPhone3G, old-bootrom iPhone3GS, or non-MC ipt2g, life is easy. redsn0w installed an untethered jailbreak and so nothing below applies.
● "Tethered" does not mean you cannot boot at all without PC/Mac assistance. If you have not installed any tweaks that hook into important programs like SpringBoard or CommCenter, your device will actually boot. However, jailbreak programs like Cydia wont work (and Cydia may still have a white icon). Also, certain built-in apps that had to be moved by Cydia will fail (Safari being the most noticeable example).
● If youve installed MobileSubstrate tweaks that hook into SpringBoard or other important programs, your boot will actually fail (youll get stuck at the Apple logo). You need to use redsn0w to "Just boot tethered right now".
Hopefully @comex will be able to untether the iOS 4.2.1 jailbreak soon!