Today, the iPhone Dev-Team is expected to update ultrasn0w and add support for iOS 5. This means that iPhone owners running the latest version of Apple’s mobile operating system will be able to download the tweak (via Cydia), and remove the carrier lock from their handset. However, there’s a catch. The unlock tool, ultrasn0w, is only compatible with specific iPhone basebands, and when you update the firmware on an iPhone, Apple can automatically update the baseband, too.
Fortunately, it is possible to stop this from happening using redsn0w, a jailbreak tool developed by the iPhone Dev-Team. In this article, we’re going to look at how you can preserve your iPhone’s baseband when updating to iOS 5. Unfortunately, the required version of redsn0w (that’s redsn0w 0.9.9b5) is only available for OS X at the moment. A Windows version is expected to launch soon, but until then, this method can only be used with Mac computers.
Furthermore, this method details how one can update the baseband only. Following this, you’ll still need to jailbreak your iPhone. For more information on jailbreaking an iOS device under iOS 5, take a look at our how-to article.
1 – Downloads
As mentioned, you’ll need redsn0w 0.9.9b5, which you can download using this link or via this section of the iPhone Dev-Team blog. You’ll also need to have downloaded the iOS 5 IPSW firmware file for your iPhone. Here are the firmware file links, which are hosted by Apple:
Once you’ve downloaded everything, plug your iPhone into your computer, turn it off and proceed to the next step.
2 – redsn0w
Now, open redsn0w and click “Extras,” and then “Custom IPSW.” Next, select the iOS 5 IPSW firmware file for your iPhone, and wait for redsn0w to process the firmware. Once processed, select “Pwned DFU.”
You’ll then be asked to put your iPhone into DFU mode, just like you do when jailbreaking via redsn0w. The instructions are displayed in the app – they are: Hold the Lock button for three seconds, hold both the Lock and Home button together for 10 seconds, and then let go of the Lock button but continue holding the Home button for a further 10-15 seconds. Don’t worry if you don’t manage to put your iPhone into DFU mode straightaway, redsn0w does give you second chances.
Once your iPhone is in Pwned DFU mode, you need to close redsn0w and open iTunes. A NO_BB firmware file will have been created by redsn0w – now we just need to restore your iPhone to that firmware file, and we’ll be finished.
3 – iTunes
Once opened, iTunes will tell you that your iPhone is in “Recovery Mode.” Don’t worry, this is the plan. Head over to your iPhone in the “Devices” section of iTunes and, while holding down the “alt” key, click “Restore.”
Now, be sure to select the NO_BB firmware file, and not the regular iOS 5 firmware file you used in step two. If you select the regular firmware file, your iPhone’s baseband will be updated and there will be nothing you can do to fix it. So be careful.
Once selected, iTunes will restore your iPhone in iTunes to the “pwned” iOS 5 firmware file. This means that iOS 5 will be installed on your iPhone, but your iPhone’s baseband will not be updated – meaning the handset will still be unlockable.
4 – You’re done!
And that’s all there is to it. Provided you follow this instructions, this is an incredibly easy method. Remember, your iPhone won’t be jailbroken – something you’ll need to do in order to install ultrasn0w. We’ll let you know once the iPhone Dev-Team releases its iOS 5 compatible version of ultrasn0w – it should be earlier today, following a planned MobileSubstrate update.
Good luck, and remember – follow the instructions, and be careful!