If you have the unlocked iPhone 4 on baseband 01.59.00 and you want to update to iOS 4.2.1, your baseband will likely be updated to 03.10.01, losing carrier unlock. Updating to iOS 4.2.1 using TinyUmbrella will protect your baseband update and later allowing you to carrier unlock 4 again. Follow the tutorial on how to upgrade your iPhone 4 to 4.2.1 preserving its baseband using TinyUmbrella.
Before proceeding you must have Saurik’s server in your host file. At the end of file add the string 126.96.36.199 gs..com useful to redirect requests for certificates for authenticity that iTunes will make to the Saurik server. You may follow the steps below to do so.
- Open Notepad with administrator privileges and then right click on the icon of notepad and click on “Open as administrator”
- Now that Notepad is open Go to folder C:/WINDOWS/system32/drivers/etc and open the file
- Add the following line at the end of the document and save it: 188.8.131.52 gs.apple.com
- Navigate to Go -> Go to Folder and enter the path /etc
- Open the file hosts with TextEdit, add the following string 184.108.40.206 gs.apple.comand save the file to your desktop.
- Now return to the previous folder by following the same method and copy the text within this file by replacing the original file (If prompted for a password enter it and click OK)
Untether Jailbreak iPhone 4 iOS 4.2.1 with Greenpois0n & Unlock using Ultrasn0w
Step 1: Update iTunes to iTunes 10.1.2
Step 2: Download TinyUmbrella from here.
Step 3: Connect your iPhone to your Mac
Step 4: Right Click the TinyUmbrella and select “Run as administrator” to open it. If you get a Windows Security Alert, make sure both boxes are checked, and hit Allow Access
Step 5: Verify that your device is currently connected, so that TinyUmbrella can detect the type of device and its firmware.
Step 6: Make sure Cydia or TinyUmbrella has an SHSH of the latest firmware. You can do this by simply clicking “Save my SHSH”. (at this point TinyUmbrella attempts to check for your SHSH blobs on Saurik’s server as well as save your current ones locally)
Step 7: Minimize TinyUmbrella (we will not be using TinyUmbrella’s TSS Server for this as it won’t allow localhost resolution)
Step 8: Open iTunes
Step 9: Backup you iPhone (anytime you do an update or jailbreak you must backup your phone)
Step 10: iTunes will offer you the update to 4.2.1 click Download and Update
Step 11: Once your installation has started it will take a couple of minutes to actually complete
Step 12: After your phone reboots for the final time iTunes will error out with a 1013 error. This is what we were looking for. Notably, the baseband has not updated.
Step 13: Close all of iTunes error pages and iTunes itself
Step 14: Go back to TinyUmbrella
Step 15: Click Exit Recovery and you phone should be rebooting and will come up to the home screen
Step 16: Go to Settings>General>About verify that you are still on the same baseband as before
Step 17: Jailbreak your iPhone 4 iOS 4.2.1 on baseband 01.59.00 using Greenpois0n RC5.
Step 18: Carrier unlock your iPhone 4 iOS 4.2.1 using ultrasn0w.
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