Follows the steps below to perform an untethered jailbreak for the iPhone 3GS ver 4.2.1. This is needed such that you do not
have to connect to computer each time you power off and restart the iPhone.
- Download Greenpois0n
- Connect iPhone to computer and start the Greenpois0n. Follow on screen instructions to jailbreak the iPhone
- Restart the iPhone. Now the phone should start up normally without need to connect to computer.