That’s a common question asked by new jailbreakers, and a challenging one to articulate by master jailbreakers. The latest version of redsn0w 0.9.6b4 will jailbreak your iOS 4.2.1 device–but depending on which device you have, your jailbreak will be either tethered or untethered.
Here’s the following explanation from the iPhone Dev Team:
Update #2:  The notion of a “tethered†jailbreak is pretty new to many people, so here’s a quick rundown on what to expect:
- If you’re 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 won’t 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 you’ve installed MobileSubstrate tweaks that hook into SpringBoard or other important programs, your boot will actually fail (you’ll get stuck at the Apple logo). You need to use redsn0w to “Just boot tethered right nowâ€.
Remember, @comex and others are working on a way to untether the 4.2.1 jailbreak. Meanwhile, the above 3 points hopefully will make it all seem less confusing 🙂
A tethered jailbreak is not fun to have when installing tweaks via Cydia. Any reboot will result in your iPhone requiring a Mac/PC to activate it again. Imagine yourself on the road and your iPhone is rendered useless. Not fun. An untethered jailbreak is in the works, but it will take some time. I’m going to wait it out for my iPhone 4.
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That just confused me EVEN MORE.
It’s like like this,
Tethered Jailbreak: Reboot your device and you have use a computer to activate the device again. Not fun.
Untethered: Device works as you would expect, reboot or not. Better.
I have a 3GS running 4.1 (jailbroken with Limerain), but don’t know whether I have an “old-bootrom iPhone3GS”. How do I find that out?
Go here for Windows: http://www.iclarified.com/entry/index.php?enid=10301
Go here for Mac: http://www.iclarified.com/entry/index.php?enid=10300
So basically stay on ios 4.1 till jailbreak 4.2 is fine
It is a pain, but if you know what you are doing, you tend to avoid reboot situations when you are on the road. I don’t want the hassle however so i will wait it out and see what happens. 4.2 does have interesting features, but nothing that would rush me into a tethered jailbreak. My wife’s phone isn’t jailbroken so i updated hers and played with “find my iphone” a handy tool.
hello there
uh… come again?
I have no clue what i have to do right now…….
i have 4.0.2 and what is the steps i need to take to unlock and jailbreak the phone?
do i update it to 4.2 and use jailbreaking thing and unlocking thing after? @_@
When there’s a proper jailbreaking tool for 4.2, we’ll post a guide.
For now, sit tight.
@yuprules hahaha
wow now your never ever going to sleep with this girl because of this. darn
Alright, so dumb question, but does tethered mean I must have my ipad tethered to the system always? Or do I only need it tethered to boot, and then unhook it and use it like normal?
Its how its all been worded, which confuses me.
ok so i have an iphone 4, i jailbroke it yesterday using cydia and it was fine until today i was changing the font using cydia and my phone froze. Now its just an apple logo and the white loading dial…help please.
ipod touch is!!!!!!! nothing but a mere brick so go use it!
just reboot your device to the computer
i jailbroke my 4s via absinthe greenpoison which is supposed to be untethered but when i shut my phone off and re booted it it gets stuck at the apple logo please help. what do i do?
Restore via iTunes and re jailbreak
so it means that u should never reboot your jailbroken tethered device ever??
Yea wat yuprules said. Im more confused than before. Its crumbled