Are you missing some key jailbreak tweaks now that you've updated your iPhone 4 or 3GS to iOS 5 firmware? Already tired of dealing with all of the shortcomings in iOS 5 notification center? Luckily if you have saved your SHSH blobs you can easily downgrade and return your iPhone to a jailbroken state (and reinstall LockInfo!)
In order to downgrade you must have saved SHSH blobs. Pictured above are how saved SHSH files appear for each firmware version in Cydia, when they are saved to Saurik's server. Follow these steps to downgrade to earlier firmware, including iOS 4.3.3 for an untethered jailbreak with JailbreakMe.
1. Download the firmware file (IPSW) for the iOS version you are downgrading to and save this file on your computer. Find the file you need here:
3. Put your iPhone into Device Firmware Update (DFU) mode. You can read how to put your iPhone 4 into DFU mode here, or read how to put your iPhone 3GS into DFU mode. The recovery mode message will appear and the iPhone screen will stay blank.
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4. Next you have to edit the hosts file on your computer to use your saved SHSH blobs instead of Apple's server. To do this on Mac OS X click the Go -> Go to Folder menu in the Finder.
Go to the folder /etc and copy the file 'hosts' to your desktop. Edit the file with TextEdit and add this line to the end of the file:
Save the modified hosts file, then drag it into the /etc folder and overwrite the old file.
Windows users will find the hosts file in C:\Windows\System32\drivers\etc\ and can open the file using Notepad. To edit the hosts file, Notepad must be run with Administrator Privileges. Right-click the Notepad icon and select Administrator Privileges to run in this mode. Add this line to the end of the file and save:
5. Return to iTunes and select your iPhone from the left menu under DEVICES. On the Mac, hold down the option key (alt) and click the Restore button in iTunes. On Windows hold down the shift key and click the Restore button in iTunes.
6. Find and choose the firmware file you downloaded during the first step. Click Open and iTunes will start restoring your iPhone to the downgraded firmware. A progress bar will appear on the iPhone.
When the process is complete, your iPhone will reboot automatically and boot up with iOS 4.3.3 or whatever firmware you chose to install. Don't forget to edit the hosts file again to delete the line '126.96.36.199 gs.apple.com' after you finish downgrading. This will insure that iTunes uses Apple's servers for future updates.
This should hold you over with an untethered jailbreak on iOS 4.3.3 until new tools are released for iOS 5. If you can't wait, there are other options including redsn0w beta for iOS 5 available now.