Today, the Dev-Team has pushed an update to their redsn0w jailbreak tool which can jailbreak iOS 4.2.1 GM on all compatible iOS devices. The latest release is redsn0w 0.9.6b3 and is exclusively directed towards the developers for now, until the public release of iOS 4.2.1 is made by Apple. This build allows developers to install custom bundles on iOS 4.2.1 GM firmware, even without having to install Cydia.
It says on the Dev-Team official blog:
(Warning: if you use the ultrasn0w unlock, please read no further…this doesn’t apply to you yet!) We’ve made some updates to redsn0w to make it easier for jailbreak developers (and tinkerers) to get their programs ready for 4.2.1. As noted above, the public version of Cydia (and MobileSubstrate too!) is not 4.2.1-compatible. redsn0w will now let you install your own custom bundles independent of Cydia (the bundle can actually be Cydia if you’ve compiled it on your own). These bundles can be up to 15MB in size, and should be in the form of a gzip-compressed tar file.
It is neither intended nor personally advised by iThinkDifferent to our loyal followers to try this jailbreak just yet unless you are a developer or an expert iOS user. We’ll keep you posted once we have the official iOS 4.2.1 release announcement from Apple and when a safer more user-friendly jailbreak is available!
Download Redsn0w 0.9.6b3 for Mac
Download Redsn0w 0.9.6b3 for Windows
Download SSH Bundle (To get the file permissions and ownerships right in your custom redsn0w bundles)
[via Dev-Team Blog]