How to Troubleshoot Greenpois0n 4.2.1

Turn the device off before you start the jailbreak.

Greenpois0n is one of many jailbreaking tools compatible with firmware version 4.2.1 on the iPhone, iPod touch and iPad. The process is simple and takes only a few seconds to complete, provided everything goes smoothly. An incomplete jailbreak might end with the word "Success!" even though there were errors behind the scenes. Even worse, your device may restart repeatedly, never making it past the Apple logo. Chronic Dev Team, the creators of Greenpois0n, resolve many issues through updates, but your own computer can be at fault.

Instructions

1. Check the list of supported devices to make sure the jailbreak is compatible with yours. Greenpois0n RC5, for example, doesn't support the iPhone 3G.

2. Launch iTunes and click "Help," "Check for Updates" before you restore the firmware. Jailbreakers use the most recent version of iTunes when testing the software; outdated versions are more likely to cause problems.

3. Follow the steps on the screen carefully when prompted to enter Device Firmware Update mode. You must press the Home and Power buttons at precise intervals or the jailbreak won't continue. Hold the buttons down securely and don't let go until you're directed to.

4. Download the latest release for 4.2.1 from greenpois0n.com. Greenpois0n RC5 had a bug that caused it to fail after launching DFU mode. Download and install the RC5_2 update or higher to avoid this particular error.

5. Install the iBooks Fix app from Cydia if you're having trouble using iBooks. The app checks to see if your device is jailbroken and if it is, certain books won't open. Specifically, it disables e-books that are protected with Digital Rights Management and affects devices running 4.2.1. You can also redo the jailbreak using Greenpois0n RC6.1, which includes the iBooks fix.

6. Download an untethered 4.2.1 jailbreak if your device displays a USB cord on the screen whenever you shut it down. The first jailbreak for 4.2.1 was tethered, meaning you couldn't turn off the device without redoing the jailbreak.

Tips & Warnings

• Jailbreaking will void your warranty with Apple.

References

• Redmond Pie: How to Fix iBooks Not Opening DRM Books Error After Jailbreaking iOS 4.2.1 With GreenPois0n
• Redmond Pie: Download GreenPois0n RC6.1 to Fix iBooks Error on iPhone, iPad, iPod Touch

Resources

• Penn State: How to Jailbreak Your iPod Touch or iPhone
• Greenpoison: Homepage
• Greenpoison: About Us
• The iPhone Wiki: Supported Devices