iPhone Dev Team have released an updated version of redsn0w 0.9.6b4 packed with the new Cydia and kernel patches for Windows and Mac OS which allows you to jailbreak final version of iOS 4.2.1 running on iPhone, iPod touch and iPad devices. This version of jailbreak tool uses Limera1n exploit instead of 24kpwn exploit used in earlier version of redsn0w tool to pwn all iOS devices for lifetime.
The bad news is that right now, the 4.2.1 jailbreak is *tethered* on all of these recent devices like iPhone 3GS (new bootrom), iPhone 4, iPad, iPod touch 2G (MC Model), iPod touch 3G and the iPod touch 4G. Old devices like iPhone 3GS (old bootrom), iPhone 3G and iPod touch 2G (Non-MC Model) can be jailbroken untethered with this version of Redsn0w.
Those who don’t know, a tethered jailbreak means that each time your device loses battery power or needs to be rebooted, you must attach it to a PC or Mac to boot into the jailbroken state. @comex is working hard on a method that may untether the 4.2.1 jailbreak, but it will require you to have your 4.1 SHSH blobs in order to use it.
Follow the tutorial below to jailbreak iPhone and iPod Touch running iOS 4.2 GM firmware. If your iPhone is already running Ultrasn0w carrier unlock, STAY AWAY from Redsn0w as it updates your baseband to the latest version, making it impossible (for now) to unlock.
How to Jailbreak iOS 4.2.1 using with Redsn0w 0.9.6b4
- An iPhone 4, 3GS, 3G or iPod Touch 4G, 3G or iPod Touch 2G (Non-MC Model on iOS 4.2.1 GM)
- iTunes 10.1 installed on your computer.
- Download iOS 4.1 and iOS 4.2.1 on your desktop
- Download Redsn0w 0.9.6 BETA 4 for Mac [Download link]
Step 1: Connect the iPod Touch or iPhone or iPad to your Mac using the USB cable.
Step 2: Update your device to iOS 4.2.1 firmware using the IPSW file you just downloaded (in pre-requisites section) via iTunes 10.1.
Step 3: Run Redsn0w 0.9.6b4 and point it to iOS 4.1 (NOT iOS 4.2.1) to proceed with the jailbreak. Click Next to continue, once the firmware has been verified.
Step 4: RedSn0w will now prepare the jailbreak data.
Step 5: You will now have a new screen where you can select packages to install. Select Cydia and other options of your choice. We would not recommend enabling Multitasking on iPhone 3G, as it will slow down the performance.
Step 6: Please plug your iPhone into the computer and make sure its OFF then click the Next button.
Step 7: You will be prompted to put the iPod Touch in DFU mode. To do so: Press the Home and Power together for exactly 10 seconds.
Step 8: Release the Power button and continue holding the Home button until RedSn0w detects the device
Step 9: Another automated process and will reboot your iPhone.
Step 10: RedSn0w will then start uploading the new RAM Disk and Kernel.
Step 11: Once the ramdisk uploading process is completed, you will be notified as “done”. Click the Finish button. When your iPhone finishes rebooting (5 minutes or so) it will be jailbroken with Cydia on the SpringBoard.
You have now successfully jailbroken iOS 4.2.1 firmware. On iOS 4.2.1, you may face some incompatibility issues with your favorite iPhone apps forcing you to return to older iOS 4.1 firmware. If for any reason, you upgraded it to iOS 4.2 and want to go back to 4.1, follow the guide posted here.
You can follow us on twitter or join our facebook fanpage to keep you updated on such iPhone, iPod Touch and iPad Jailbreak Guides. You may also like to check out following apps and tools after jailbreaking your iPhone.