Untethered Jailbreak Guide for iPhone 4 and 3GS on iOS 4.2.1

You may already know Greenpois0n has been released. The debut of Greenpois0n is prominent as it is the first stable jailbreak tool that supports untethered jailbreak on all devices running iOS 4.2.1. Unlike the Redsn0w 0.9.7, the tool doesn’t require you to have the SHSH blobs. You can simply jailbreak your device running iOS 4.2.1 out of the box.

Presently, the Greenpois0n is available on Mac platform only. If everything goes well, the Windows version will be released very soon (hopefully in these few days). Update: The Windows version is now available. I have tried to jailbreak my iPhone 4 using Greenpois0n. Despite there are a few hiccups, overall speaking, the jailbreak process is quite smooth.

Here I come up a step-by-step jailbreak guide to walk you through the process using Greenpois0n. If you’re using iPhone 3GS or iPhone 4 and would like to jailbreak your device on iOS 4.2.1, you can simply follow the procedures and achieve the jailbreaking.

Before we dive into the jailbreak process, please read through the notes very carefully:

• As of now, the Greenpois0n is available for Mac user only. For Windows user, you have to wait for a few days before the official release. Update: The Windows version is now available.
• Greenpois0n is a jailbreak solution that allows you to open up your device to install 3rd-party applications. It’s not a software-unlock solution. So if you are currently relying on Ultrasn0w to unlock your iPhone, please DO NOT upgrade your iPhone to iOS 4.2.1 directly. Otherwise you’ll lose the unlock and your iPhone will not be able to make call.
• Greenpois0n does not come with hacktivation. That means you have to activate your iPhone before using the jailbreak tool.
• Greenpois0n works only on iOS 4.1 and 4.2.1. However this guide is written based on the jailbreaking of iOS 4.2.1.
• Make sure you’re using iTunes 10.1 or up.
• If you have used Redsn0w to jailbreak (untethered) your iPhone, I suggest you to restore it to iOS 4.2.1 via iTunes before using Greenpois0n.

Note: If you have any questions after reading the note, feel free to leave us comment before kicking off your jailbreak journey.

Okay, let’s get started.

Preparation for the Jailbreak

1. Download Greenpois0n RC5_2 from greenpois0n.com or mirror site.

Note: I suggest you to download the tool from the mirror site. The official site is extremely busy and not very stable.

2. Extract the greenpois0n-osx_rc5_2.zip and you’ll have the “Greenpois0n” application.

Kick-off the Jailbreak Process

3. Connect your iPhone to computer via USB cable and power it off.

4. Launch the Greenpois0n application.

5. Click the “Jailbreak” button to kick off the jailbreak process. You can simply follow the on-screen instructions to put your iPhone into DFU mode. Keep holding the home button till the end of the jailbreak process.

Note: If you fail for the first time, just quit Greenpois0n, power off your iPhone and goes through the process again. It won’t hurt.

6. As you successfully put the device into DFU mode, Greenpois0n will automatically jailbreak your device. On your iPhone, you’ll see a series of status messages in command mode. That’s normal. Just wait until Greenpois0n tells you the process completes.

Installing Cydia

7. After jailbreaking, your iPhone will be automatically booted up. You should find a new icon called “Loader”. Simply tap on the icon and launch the app.

8. Once launched, tap on the “Cydia” button to install cydia. This will initiate the download process. Just wait for it to complete and you’ll have cydia installed on your iPhone.

Note: If you found the cydia button missing after launching Loader app, just quit it and try again.

9. After successfully installing cydia, you can tap the “Option” button and remove the Loader app.