Chronic Dev Team have already released an updated version of Greenpois0n untethered jailbreak tool that allow you to jailbreak iPad on iOS 4.2.1 firmware apart from jailbreaking iPhone 4, iPhone 3GS, iPod Touch 4G on iOS 4.2.1. Follow the complete tutorial on how to jailbreak iPad 4.2.1 using Greenpois0n RC5 tool on Mac OS X.
How to Jailbreak iPad 4.2.1 using Greenpois0n RC5 on Mac OS X
Step 1: Download Greenpois0n RC5
Step 2: Now move the greenpois0n-osx_rc5 on your desktop and unzip it.
Step 3: Open folder and double click Greenpois0n icon to launch it.
Step 4: Connect iPad 4.2.1 to the computer, power it off and then click the large Jailbreak button.
Step 5: Greenpois0n will display the instructions to put the device in DFU Mode. You will then be asked to press and hold the sleep button for 3 seconds.
Continue holding sleep; press and hold home for 10 seconds.
Release sleep button; continue holding home for 15 seconds.
Step 6: Once your iPad iOS 4.2.1 is in DFU mode, the jailbreak will begin.
Step 7: Greenpois0n will now jailbreak your iPad 4.2.1. Click the Complete button once the software application has completed.
Step 9: After the iPad restarts you’ll notice a new Loader app on your Springboard, entitled “Greenpois0n”. Press to launch it.
Step 10: Press to select Cydia then press the large Install Cydia button that appears.
Step 11: Once Cydia has installed successfully on your iPad, you will be prompted if you want to remove Loader from your device. Press the Remove button then press the Home button. Your iPad will now reboot.
You have successfully jailbroken your iPad [WiFi or 3G] on Mac running iOS 4.2.1.
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