How To Preserve iPhone Baseband Using sn0wbreeze While Upgrading To iOS 4.2.1 ~ Blog O'Nerd

What a week this was! first, Chronic Dev Team released Greenpois0n to jailbreak iOS 4.2.1 untethered, then yesterday iPhone Dev Team released PwnageTool 4.2 that uses greenpois0n's exploit and lets you create custom IPSWs on MAC that are pre-jailbroken untethered. Then iH8sn0w released sn0wbreeze 2.2 that uses same stuff PwnageTool 4.2 uses from greenpois0n and lets you create custom pre-jailbroken IPSW on Windows and MAC. Must say that good days are going with the jailbreak scene.

If I talk about myself, I haven't done anything new with my iPhone 3GS since some time. And I wasn't going to do either. But today I decided to update iOS 4.0.1 to 4.2.1. As you may know, I rely on carrier unlock and so I need to jailbreak my device and then I can unlock it. There was a tethered jailbreak available from iPhone Dev Team but I didn't want to get it tethered, so I waited for a way to preserve my current baseband so I can unlock my device. And when sn0wbreeze got released, I thought to give it a try. Read more to know how to use sn0wbreeze by iH8sn0w to preserve your current iPhone baseband while upgrading to iOS 4.2.1.

What is "Preserving Baseband"?
Preserving Baseband means, to retain your current baseband version while updating your device's firmware. Every firmware version (mostly) changes the baseband version too. For example, baseband version in iOS 4.0.1 was 5.13.04. It was 5.12.7 in iOS 3.1.3 if I'm not mistaken.

Why I should preserve baseband?
If you want to unlock your iPhone, the unlock must support your baseband. So if the unlcok does not support the current baseband, you can't unlock your device and need to wait until it supports the baseband. If you want to upgrade your device's software but don't want to update the baseband, then you need to "Preserve" it's baseband.

Please read : You should follow this tutorial only if you have official carrier SIM so that you can activate your device after you restore it via iTunes using this custom IPSW. If you don't have official SIM, then read my next article that will cover how to preserve baseband, jailbreak, activate and unlock your device. ~~Wait for that please.~~ The tutorial is posted Here.

Things you need

iPhone on any firmware released before iOS 4.2.1. (like 4.0.1, 3.1.3 or any)
The IPSW for iOS 4.2.1 downloaded from apple. (Link at the end)
Latest iTunes (10.1 or later)
sn0wbreeze v2.2 (Download links at the end)
Official SIM in order to activate iPhone. If you don;t have it, you need to hactivate. Tutorial will be posted later.

Things used in this tutorial.

iPhone 3GS (MC,New Model) on iOS 4.0.1, jailbroken with limera1n, unlocked with ultrasn0w.
iTunes v10.1.2.17
sn0wbreeze 2.2
Windows 7 x86

Note : Read the steps carefully. If anything goes wrong with your device while following this tutorial, don't blame us.
Note : You may void your device's warranty if you follow this tutorial.
Note : Be warned that if anything goes wrong, you will update your baseband and will loose your unlock. Proceed at your own risk.

How to preserve baseband while upgrading to iOS 4.2.1?

Step 1

Download the appropriate IPSW fie for your device from apple.
Download sn0wbreeze 2.2
Download iTunes 10.1 or later from apple.

After all downloads are completed, follow step 2.

Step 2

Run sn0wbreeze 2.2
The home screen looks like this.

Click an image to enlarge

Read the warning and click OK
It will show another screen like this.

Click next button

Step 3

Now its time to select the IPSW file you have downloaded from apple.
Click Browse button and browse to the IPSW file you have downloaded from apple, and click open.
Now sn0wbreeze will identify the IPSW file. If all is good, it will show the next screen confirming IPSW verified.

Click next.

Step 4

Now you'll see screen with three options - Baseband Preservation Mode, Simple Mode and Expert Mode. The later two modes are for jailbreak. We need the first one. So click Baseband Preservation Mode and click next.

Now sen0wbreeze starts process for cooking custom IPSW file for your device. It will prompt you if you want to play PacMan while ISPW is being cooked. Useless as you won't be able to complete even one game before IPSW is cooked. Click No thanks or PacMan button. Your choice.

Step 5

When sn0wbreeze shows Done! message, click OK.

The custom IPSW file created by sn0wbreeze will be located on your desktop.

Now we need to upgrade to iOS 4.2.1 using this custom IPSW. So follow next step.

Step 6.

Now we need to enter into Pwned DFU mode in order to use custom IPSW to restore device. So follow onscreen instructions to enter DFU mode.

Note: You better follow steps shown on sn0wbreeze to enter DFU and not written below. I might have missed something.

First power off device.
Then press Sleep button for two seconds.
Now keep pressing the slepp button, press the Home button. Hold them both for 10 seconds.
Now release the Sleep button while still holding the Home button. If succeeded, sn0wbreeze will start exploiting and put your device in pwned DFU mode. (Your Device's screen will be blank)

Click OK when it says your device is PWNED DFU Mode.
Close sn0wbreeze.

Step 7

Now open iTunes.
It will say that it needs to check for software updates. Allow it to do so.
Not it will say that iTunes has detected iPhone in Recovery Mode. Click OK.

Step 8

Now we need to use custom IPSW file we created with sn0wbreeze in order to update.
So press shift button on your keyboard and click the "Restore" button in iTunes.
Browse to desktop and select the custom IPSW file we created and it will say that your device will be updated to iOS 4.2.1. Click OK.
Now iTunes will start the process to install the iOS to your device. It may take several minutes so sit back and enjoy the process.

Step 9

If you have official carrier SIM, insert it now and let iTunes verify it with apple server. Now it will activate your iPhone. If you don;t have official SIM, you'll need to jailbreak via sn0wbreeze if order to "Hactivate" your iPhone. ~~I'll post the tutorial later~~ Tutorial Is Posted Here.

Step 10

Now iTunes will ask if you need to setup a new iPhone or use last backup. Choose restore from last backup if you want all your data you had while you synced last. Or select setup new iPhone if you want to start from scratch. I recommend you choose to setup new iPhone as battery draining issues are reported if you restore from backup. Your choice again.

Step 11

Now all you need to do is to check if all has gone well. Keep your fingers crossed and open Settings. Select General and select About. Scroll down to see Version (should be 4.2.1(8C148a)) and Modem Firmware which must be the same before you restored. It was 5.13.04 for me as I was on iOS 4.0.1. If it has been upgraded too, you're out of luck and need to wait for an unlock.

Here's mine.

OK so we're done upgrading to iOS 4.2.1 while preserving baseband version. Have fun.

If you need any help, feel free to ask.

For more tutorials, follow me on Twitter and join Facebook Group.

Download Links

Download iOS 4.2.1 IPSW.
iPhone 4
iPhone 3GS
iPhone 3G
iPad
iPod touch 2G
iPod touch 3G
iPod touch 4G

Download sn0wbreeze 2.2

Note : The next post coming out shortly will cover " How to create a custom IPSW that will activate and jailbreak your device on iOS 4.2.1. Stay tuned.

Update 1 : Tutorial Posted - How to upgrade to iOS 4.2.1 while preserving your baseband, activate and unlock.

Related Tutorial : How To Enter Pwned DFU Mode And Use Custom IPSW Firmware

This tutorial was brought to you by iambl0gger.

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