Jailbreaking Ipod iTouch iOS 4.2.1 Using GreenPois0n RC5 Untethered

I just jailbroken my Ipod iTouch version 4.2.1 using GreenPois0n and it is also compatible in iPhone version 4.2.1

The following instructions will help you jailbreak iOS 4.2.1 on iPhone 4, 3GS, iPod touch 2G/3G/4G, iPad and Apple TV 2G using GreenPois0n.

NOTE: If your iPhone 4 rely on an unlock, do not update to iOS 4.2.1 yet as doing so will upgrade your baseband, making it impossible for now to unlock.

Step 1: Download GreenPois0n Here (Just Choose what OS you have)

Step 2: Connect your iPod/iPhone via USB to your computer and click on “Jailbreak” as seen in the screenshot below.

Just click Prepare to Jailbreak

Step 3: Now follow the following onscreen instructions to enter DFU mode:

• Press and hold the sleep button for 2 seconds
• Continue holding sleep; press and hold home for 10 seconds.
• Release sleep button; continue holding home for 15 seconds. 

Step 4: GreenPois0n will now start “Jailbreaking” your iOS device untethered on 4.2.1.

You will see this on your iDevice

Step 5: Your iPhone, iPad or iPod touch should now be successfully jailbroken on iOS 4.2.1. Now start “Loader” found on the homescreen and install Cydia.

Video Tutorial

Credits to RedMondPie for the Guide