Jailbreakopolis | Jailbreaking iPhones iPods iPad: Jailbreak for iOS 4.2.1 | How to Jailbreak Your iPhone, iPod and iPad

If you cannot wait for the final release of redsn0w to jailbreak your iPhone, iPod and/or iPad, follow these 8 easy steps to tether-jailbreak your iDevices using redsn0w 0.9.6b4!

On November 23rd, 2010, The iPhone Dev Team released Redsn0w 0.9.6b4.
Redsn0w 0.9.6b4 brings about the first jailbreak, with a working Cydia app and MobileSubstrate,to all iOS 4.2.1 devices.

The one nuisance is that it's a tethered jailbreak for the newest devices. Having a tethered jailbreak means you will have to connect your jailbroken iOS device,to your computer, and execute the Redsn0w 0.9.6b4 program again in order to regain your jailbreak status on every reboot. This "re-jailbreaking" process actually takes much less time than the initial jailbreaking of your device.

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Disclaimer: This guide is for testing and educational purposes only, not to encourage piracy. We cannot be held responsible for any damage done to your device or firmware during the process.

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Redsn0w 0.9.6b4 provides:

1) an untethered jailbreak of iOS 4.2.1 for:

iPhone 3G
older iPhone 3GS
non-MC iPod touch 2G

2) a tethered jailbreak for:

iPhone 3GS (new bootrom)
iPhone 4
iPad
iPod touch 2G (MC model)*
iPod touch 3G
iPod touch 4G

* To find out which model you have, go to Settings => General => About, and then scroll down to "model". The model number there will start with MC (MC model) or MB (not MC model).

MuscleNerd of iPhone Dev-Team has confirmed that the next version of Redsn0w will be released just before Christmas 2010 and will include an option which will allow you to untether your iPhone jailbreak on iOS 4.2.1 without having to restore your device.

UPDATE: Although the iPhone Dev-Team has not released a final jailbreak thus far, they have released numerous beta releases to developers to test on the 4.2.1 iOS firmware.

WARNING: Those of you who rely on a carrier unlock MUST STAY AWAY from Redsn0w and iOS 4.2.1.

Follow the step by step instructions posted below to jailbreak iOS 4.2.1 with Redsn0w 0.9.6b4: Step 1: Download iOS 4.2.1 for your version of iOS device.

Download iPhone 4 IPSW
Download iPhone 3GS IPSW
Download iPhone 3G IPSW
Download iPad IPSW
Download iPod touch 2G IPSW
Download iPod touch 3G IPSW
Download iPod touch 4G IPSW

Step 2: Download Redsn0w 0.9.6b4 for your system:

Download Redsn0w 0.9.6b4 for Mac

Download Redsn0w 0.9.6b4 for Windows

Step 3: Using iTunes 10.1 or newer, Update/Restore to iOS 4.2.1 firmware using the IPSW file you just downloaded. Your device needs to be connected to your computer via USB for this step and beyond.

(If you are using the 'Restore' option to upgrade your device, hold down 'Alt' key and click on Update or Restore, then navigate to the IPSW file you just downloaded and double-click/select)

Step 4: Start Redsn0w 0.9.6b4 and point it to iOS 4.2.1 firmware to proceed with the jailbreak.

Step 5: Now select “Install Cydia” and click “Next”.

Step 6: Make sure your device is both OFF and PLUGGED IN
to the computer, via USB, before you click “Next”.

Step 7: You will now be instructed to follow a few steps in order
to place your device in to the DFU mode by:

Quickly hold down the "Power" or "Sleep/Wake" button located on the top of your device.
Keep holding down the "Power" or "Sleep/Wake" button
AND hold down the "Home" button, for 10 seconds.
Release the "Power" or "Sleep/Wake" button but keep holding “Home” button for 15 seconds or until installation begins.

how to dfu mode Home button and sleep/wake button diagram

Step 8: Sit back and enjoy while redsn0w will do all the rest for you. Once done, your iPhone or iPod touch will restart automatically and you will find it jailbroken on the latest iOS 4.2.1 firmware.