Yesterday, Apple released the iOS 4.2 Beta firmware for iPhone, iPod Touch and the iPad. But now, only the developers can grab it as it is a beta release. The PwnageTool bundle have been released to jailbreak iOS 4.2 firmware on the iPhone 3GS (Old Bootrom). Another main thing to note is that your iPhone 3GS should be jailbroken earlier with redsn0w, blackra1n, Sn0wbreeze or the PwnageTool. This guide doesn’t support any other guide. So please be careful about proceeding to this iOS 4.2 beta jailbreak and read all the description given here before you start the jailbreak process.
NOTE : Since Cydia is not supported now on the iOS 4.2 Beta firmware, you will have to install OpenSSH manually so that you could install things. You could get OpenSSH from here : http://apt.telesphoreo.org/cydia/debs/openssl_0.9.8k-9_iphoneos-arm.deb and http://apt.telesphoreo.org/cydia/debs/openssh_5.2p1-8_iphoneos-arm.deb/
Again I am telling you, proceed to this only if you are well known with these and only if you are sure. Be careful and do any mistakes and damage your phone. So try it at your own risk. We are not responsible for any damage.
Do Read : Downgrade iOS 4.2 to iOS 4.x or lower
1. Download iTunes 10 for Mac OS X if you don’t have it.
2. Download iOS 4.2 Beta for iPhone 3GS from here.
3. Download PwnageTool 4.01 from http://rapidshare.com/files/401909987/PwnageTool_4.01.dmg
4. Download PwnageTool bundle from here and extract it.
5. Move all the files to the desktop.
6. Now copy the bundle to the PwnageTool by right clicking on it, choosing ” Show Package Contents “, browsing to Contents -> Resources -> Firmware Bundles and then copying it there.
7.Â Launch PwnageTool.
8. Choose your iPhone 3GS with iOS 4.2 and go forward.
9. PwnageTool will detect the iOS 4.2 firmware. Move forward.
10. When PwnageTool ask you â€ Do you have an iPhone contract that would activate normally through iTunes? â€œ, click on â€œNoâ€ if you are not on an officially supported carrier. Click on â€œYesâ€ only if you are having an officially supported carrier on your phone like the AT&T. PwnageTool will now begin to create the IPSW file. When the process is completed, a â€ ihaz Success! â€ message will be shown.
11. Now open iTunes and select your iPhone 3GS in it.
12. In Windows, hold the Shift key and in Mac OS X, hold the option key and click on â€ Restore â€œ.
13. Browse to the iOS 4.2 .ipsw file that PwnageTool cooked earlier and let iTunes do the rest of the iPhone 3GS iOS 4.2 jailbreak process. After the process is finished, your phone will automatically reboot and it will be jailbroken on iOS 4.2.
Thanks : RedmondPie