GreeniPois0n RC6 jailbreak is released to do an untethered iOS 4.2.1 jailbreak on Apple TV 2G. The RC6 jailbreak tool is available for download both for Mac OS and Windows. Posted below is the HOW TO GUIDE for an untethered iOS 4.2.1 jailbreak on Apple TV 2G using GP RC6.
STEP 1: Download Greenpois0n RC6 Jailbreak Tool For Mac OS or Windows.
STEP 2: Unzip or Extract the gp-win_rc6_final or gp-mac_rc6_final file.
STEP 3: Connect the Apple TV device with your computer and Launch the Greenpois0n application by clicking on it. It will open the following window. Choose Yes to continue.
STEP 4: It will prompt you instructions to put your Apple TV 2G device into DFU mode. It will prompt you instructions which are self explanatory.
STEP 5: Now your device is in the DFU mode. Click on the big Jailbreak Button. In case of Apple TV 2G. it takes much more time as compared to iPhone, iPad or iPod Touch.
STEP 6: The rest of the jailbreak process will be done by the Greenpois0n app. Let the process to be completed.
STEP 7: After the jailbreak process is completed, you can unplug Apple TV device from your computer and connect it with your TV.
STEP 8: You will see a Greenpois0n Skull instead of an Apple Logo. Click on Greenpois0n Tab and the “Inject Software”. Now you have to open the new browser window to install Cydia.
Thats it, you are done!