Redsn0w v0.9.6b3 has been released to jailbreak iOS 4.2.1 GM on Windows and Mac OS X. Please note that this Redsn0w update is only for for developers so that they might get their jailbreak-apps ready for iOS 4.2.1. Moreover the current public release of Cydia and MobileSubstrate is not compatible with iOS 4.2.1 GM but with OpenSSH and OpenSSL SSH bundle, you will be able to install packages without Cydia by using the tethered boot option in Redsn0w 0.9.6b3.
Redsn0w 0.9.6b3 supports tethered jailbreak on all iDevices except iPhone 3G, iPhone 3GS (Old-bootrom) and iPod Touch 2G (non-MC). So if you have any other iDevice, DO NOT use this Redsn0w update as it will require you to put your iDevice into jailbroken state on every restart by using "Just boot tethered right now" option in Redsn0w 0.9.6b3.
Usage of Redsn0w 0.9.6b3 is simple. Just download iOS 4.2.1 GM from here and restore it on your iDevice using iTunes. Start Redsn0w 0.9.6b3, browse to iOS 4.1 IPSW (NOT iOS 4.2.1 IPSW) and choose "Install custom bundle" and "Just boot tethered right now" option. Follow the on screen instructions to put your device in DFU mode and jailbreak it on iOS 4.2.1.
Download Redsn0w 0.9.6b3 for Windows
Download Redsn0w 0.9.6b3 for Mac
Download SSH Bundle for OpenSSH & OpenSSL access
Download iOS 4.1 Final for iPhone 4/3GS/3G & iPod Touch 4G/3G/2G
Download iOS 4.2.1 GM Seed for 4/3GS/3G, iPod Touch 4G/3G/2G & iPad (Wifi+3G)
You may also like to read:
- Jailbreak iOS 4.2.1 GM on iPod Touch 4G with PwnageTool Bundle [How-To Guide]
- Jailbreak iOS 4.2.1 GM on iPad with PwnageTool Bundle [How-To Guide]