Jailbreaking and unlocking the iPhone 4 on 4.2.1 firmware using redsn0w

Updated: February 5, 2011

Who is this guide for?
  • iPhone 4
  • Cydia must have your 4.2 Beta 3 firmware SHSH on file.
  • You must have access to the 4.2 Beta 3 firmware.
  • I used iTunes 10.1.1.
  • I used OS X 10.6.6.


Thanks again go out to the iPhone Dev Team for providing this amazing, and FREE program for customizing the iPhone. You can visit their website here, and their blog here. You can read their notes regarding this beta version of redsn0w here.





Attention: The creator of TinyUmbrella has posted a newer process for getting the iPhone 4 onto 4.2.1 firmware while preserving your unlocked modem firmware. This process is exactly the opposite of what I'm documenting here. He now proposes you restore instead of update to get to 4.2.1. You do this at your own risk. I've already burned one of my iPhone 4s by restoring and using TinyUmbrella. I then updated to preserve the baseband on another one of my iPhone 4s and it worked that time using the instructions presented in this tutorial. If someone wants to send me their iPhone 4 to risk on his new instructions I'd be happy to offer those instructions as well. To read these alternate instructions simply go to the TinyUmbrella website linked to below. One of the advantages to his method (if it works) is you wouldn't need the 4.2 Beta 3 firmware or SHSH.



Step 1.

Download iOS 4.2.1 firmware for the iPhone 4 from Apple here:

http://appldnld.apple.com/iPhone4/061-9858.20101122.Er456/iPhone3,1_4.2.1_8C148_Restore.ipsw

Download redsn0w 0.9.7b6 from the iPhone Dev Team in the update 6 section of their blog post here.

Now place your 4.2 Beta 3 firmware file (you can obtain this file if you are a member of the Apple Developer Connection, learn more here: http://developer.apple.com) with these files. You should have these three icons on your desktop.

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If your downloaded firmware file ends in .zip, rename it to end in .ipsw. Note: Safari likes to open "safe" files by default. You must turn this feature off for this download to work correctly. Click "Safari", select "Preferences", from the "Geneal" tab uncheck the box that says "Open "safe" files after downloading". Otherwise just use Firefox to download this firmware file.

Double click the redsn0w file and it will place a folder on your desktop. Go into this folder and place the redsnow.app file into your Applications folder on your computer. Overwrite any previous versions.

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Here I am on 4.1 firmware and 01.59.00 modem firmware

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Step 2.

Launch TinyUmbrella and connect your iPhone. Ensure you have the 42b3 SHSH or else you won't be able to jailbreak. It may be best to click the Save SHSH button to grab any and all SHSHs available. You can download TinyUmbrella here.

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You can also check for the 42b3 SHSH by launching Cydia.

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Back in the TinyUmbrella program, click the Advanced tab and ensure the box is checked for "Set Hosts to Cydia on Exit."

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Another way to verify you have the correctly edited hosts file is to go to your Applications folder, then go to the Utilities folder and launch the Terminal. Enter the following:

sudo nano /private/etc/hosts

You'll be prompted for your password so enter it.

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If you see the line 74.208.10.249 gs.apple.com then you are good to go. This means that any requests to the Apple verification server will instead be directed to the Cydia server. Ensure this line does not have a # symbol at the beginning! Double check this, especially if you happened to start the TSS server and then stopped it previously. If you screw this up your modem firmware will be updated and you will be unable to unlock at present.

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Step 3.

Launch iTunes. Press your option key while clicking Update. Do NOT click Restore!

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Navigate to your 4.2.1 firmware, select it and click Choose.

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This message better say update and not restore.

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The updating process will take several minutes.

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A status bar on the iPhone will display the progress of the update.

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When the process completes you'll receive a pop up with error 1013. Click OK.

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Another pop up will appear. Click OK.

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The iPhone will display the connect to iTunes graphic.

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Go back to TinyUmbrella. Select the iPhone in the Recovery Devices section, then click the Exit Recovery button. The iPhone will boot. If you launch Settings, and go to General, About you'll see at this point that you are on 4.2.1 firmware and still have your 01.59.00 modem firmware.

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Step 4.

Launch redsn0w. Click the Browse button.

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A file browser will open. Navigate to your 4.2.1 firmware file, select it and click Open.

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The ipsw should be identified. Click Next.

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A pop up window will appear.

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Redsn0w will present a few options. Install Cydia is already checked.

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  • Install Cydia is for adding the Cydia program to gain access to the jailbreak community of applications.
  • Jailbreak Monte (untether) is for jailbreaking 4.2.1 firmware which requires access to the 4.2 Beta 3 firmware.
  • Install custom bundle is for adding your own .tgz or .tar.gz files to the jailbreak. When you select this a file browser window will open.
  • Just boot tethered right now - is for those that are already jailbroken via a tethered method and need only reboot, not jailbreak all over again.
  • Just enter pwned DFU mode right now - walks you through DFU mode used for restoring purposes.



Check the box for Jailbreak Monte (untether) and a pop up window will open. Click OK.

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Navigate to your 4.2 Beta 3 firmware, select it and click Open.

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Jailbreak Monte (untether) will now be checked. Click Next.

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Turn off the iPhone, ensure it is connected via USB and click Next.

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Instructions for entering DFU mode will appear. They start right away and go very quickly so try to keep up! First hold down the Power (sleep/wake) button for three seconds.

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Keep holding on to the Power button, and press and hold the Home button for 10 seconds.

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Continue holding the Home button, and release the Power button.

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Redsn0w will display various messages: Jailbreaking, Preparing Jailbreak Monte, JB Monte: Extracting encrypted filesystem, Extracting kernel, Decrypting main filesystem, Extracting system files, Finished preparation, Waiting for iPhone4, Fetching SHSH blobs, Exploiting with limera1n, Uploading first stage, Waiting for reboot.

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You'll see a graphic that says jailbreak data is being downloaded on the iPhone. Redsn0w will display more messages: Uploading logo, Uploading ramdisk, Uploading kernel, Rebooting. You will see the message: Waiting to send Jailbreak Monte files for about 2:30. In the mean time text will scroll on the iPhone's screen.

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You will see a few different messages (Installing base utilities, Replacing kernel, Flashing NOR, Installing bundles, Activating, Syncing file systems, Moving Applications, Rebooting) on your iPhone during the next couple minutes. The iPhone will reboot once this has finished.

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Done will appear in the program.

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Step 5.

Launch Cydia. Don't worry about the icon being white right now. The next screen will state that the file system is initializing for about one minute. The iPhone will then respring. Launch Cydia again. My screen freaked out at this point (it's done it before using this jailbreak). Cydia will show you have updates and the Apple logo and possibly the spinning wheel will appear and will flicker. I pressed the Upgrade Essential button. Confirm the installation at the next screen.

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Press the Reboot Device button. The Cydia icon should look normal now. Launch it.

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Press the Search button. Enter ultrasn0w.

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Install the program. Press Reboot Device.

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You'll most likely receive this message next. I have no idea what the ramifications are.

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Here I am on 4.2.1 firmware and 01.59.00 modem firmware. If you do not have a carrier signal try rebooting (several times). You may also need to launch Settings, press General, press Network and then turn off your 3G service for ultrasn0w to work. This is normal.

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