Plenty of people will have upgraded to iOS 5.1 after its March 7 release. Although we wrote about a warning issued by the iPhone Dev Team regarding the latest iOS update, many people must have gone ahead and updated their firmware regardless. If you have done so, and miss your untethered jailbreak, or have some other issue and want to downgrade to an older version, you can now do so.
As long as you have the SHSH blobs of whatever particular firmware you wish to downgrade to, downgrading should not be a problem. To check if you do have the SHSH blobs saved, open Cydia and the top of the main page of your Cydia account should notify you.
Please note that unless Apple is signing the firmware you wish to go back to, iPhone 4S cannot be downgraded to that particular version. Only older devices can be downgraded to iOS 5.0.1 (custom firmware only) and iOS 4.x, given that users have the SHSH blobs and APTicket saved for that version.
SHSH blobs cannot be saved after Apple stops signing the firmware you wish to downgrade to. iPad 2 users can downgrade back to iOS 4.x but only if they have the SHSH blobs saved.
How to downgrade to iOS 5.0.1/5.0 custom firmware using iFaith:
Only iPhone 4, 3GS, iPad 1, and iPod touch users can downgrade back to iOS 5.x using iFaith and the method detailed below:
Step 1: Download the latest version of iFaith for Windows by clicking this. Also download the official stock iOS firmware from here.
Step 2: Click on ‘Build *signed* IPSW w/Blobs’ to build a signed firmware file.
Step 3: Browse for the previously saved SHSH blobs, which will allow your device to be downgraded to the old firmware. iFaith will then ask you to select the stock firmware from which the custom firmware file will be created. Once selected, a new custom firmware will be created and placed on the desktop. This will have the SHSH blobs incorporated into it.
Step 4: Enter DFU mode using iFaith. Now simply use iTunes to restore to this custom firmware file.
How to downgrade to iOS 4.3.5 or below:
The following instructions work with the same devices that the ones given above are for. That is, for iPhone 4/3GS, iPad 1 and iPod Touch. Both sets of instructions do not apply to the iPhone 4S. But the ones given below work for iPad 2 as well. The SHSH blobs required for the iOS 4.x firmware will either be saved on Cydia or by using TinyUmbrella.
Step 1: Download the iPSW of the firmware version you would like to go back to:
- iOS 4.3.5
- iOS 4.3.4
- iOS 4.3.4
Step 2: Connect your device to your PC/Mac .Next, put it into pwned DFU mode by using the latest version of Redsn0w (0.9.10b6). The pwned DFU option should be in ‘Extras’.
Step 3: Find your hosts file so you can edit it. For Windows, go to Windows > System 32 > Drivers > etc. For OS X just go to etc. Back up the file, and then open it using a text editor (notepad, for instance).
Step 4: Copy and add the text given below, to the bottom of the file that you have just opened.
Step 5: Open iTunes, and select your device from the list given to the left. Hold down the Shift button (for Windows) or the Alt button (for OS X) and click Restore. Locate the iOS 4.x iPSW that you selected in the first step.
Step 6: The Error 10xx is to be ignored, if it pops up. Use either TinyUmbrella or Fix Recovery to kick it out of recovery mode.
And that’s it; you’re done with a fresh installation of whatever firmware version you chose. Since the reason most people will wish to downgrade is an untethered jailbreak (only a tethered jailbreak has been released for iOS 5.1) users of an iPhone 4, 3GS, iPad 1, or iPod Touch can use Redsn0w orSn0wbreeze to jailbreak on iOS 5.0.1.
Note: Place your backup hosts file back in its folder to continue to receive updates from Apple in the future.