Chronic Dev Team recently released Greenpois0n jailbreak tool (untethered) for Mac that lets you jailbreak iOS 4.2.1 firmware on 4, iPhone 3GS, iPod Touch 4G, iPod Touch 3G and iPad without requiring SHSH blobs for iOS 4.2b3. Ultrasn0w unlockers “PLEASE” remember not to update to stock 4.2.1, else you will lose unlock. Follow guide listed below on how to jailbreak (untethered) iPhone 4, iPhone 3GS on iOS 4.2.1 using Greenpois0n Tool on Mac OS X.
How to Jailbreak iOS 4.2.1 Untethered on iPhone 4, 3GS with Greenpois0n RC5
Step 1: Download Greenpois0n .
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 iPhone 4, 3GS 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 prompted 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 4, iPhone 3GS is in DFU mode, the jailbreak will begin.
Step 7: Greenpois0n will now jailbreak your iPhone 4 on iOS 4.2.1. Click the Quit button once the software application has completed.
Step 9: After the iPhone 4 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 iPhone 4, 3GS; you will be prompted if you want to remove Loader from your device. Press the Remove button then press the Home button. Your iPhone device will now reboot.
You have successfully jailbroken iPhone 4, iPhone 3GS on Mac OS X running on latest firmware iOS 4.2.1.
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