Disclaimer: This guide is for educational and entertainment purposes only. Neither TiPb nor the author take any responsibility for any problems/issues/bricking/etc. that may occur while using this or any software to modify your iPhone. Please be aware of what you are doing. If you're not sure, don't do it.
Note to New Macbook Owners - if you have a late 2008 model aluminum MacBook, MacBook Pro, or MacBook Air and have not previously Pwned your iPhone (under firmware 2.1 or earlier), the issues we blogged about previously mean you will have to use a different computer to Jailbreak 2.2.1. Sorry folks. If you have already Pwned under 2.1 or previous, then you can simply put your iPhone into recovery mode and restore with the freshly created IPSW. (If you don't understand what all that means, keep reading, or go to our Jailbreak Central Forum for help)
blockquote>This applies if you have a locked iPhone 3G and you wish to update to 2.2.1 but preserve the iPhone’s current baseband software. Preserving the baseband will ensure that you can still use “yellowsn0w” the iPhone 3G unlock application. To upgrade your phone to 2.2.1 and preserve the state of the baseband you need to create a custom .ipsw with PwnageTool. This custom .ipsw will not contain the baseband update but of course will still give you any new stuff from 2.2.1
*You must be on firmware 2.2 or below in order to preserve your baseband. If you are already on 2.2.1 prior to Jailbreaking you will not be able to unlock your phone.
Let’s get started, after the jump!