Jailbreaking the iPhone 4 on 4.2.1 firmware using redsn0w

Updated: January 10, 2011

Who is this guide for?
  • iPhone 4 owners with an authorized SIM card (there is no unlock).
  • 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.






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. Note all redns0w graphics showing a version number will be outdated images. The team is releasing beta updates much too rapidly for me to bother with creating new screen shots. The process is still the same as described.

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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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Step 2.

Launch Cydia and verify that it has your 42b3 SHSH on file. If it does not, then you won't be able to follow this tutorial.

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If you want to continue, then restore your iPhone to 4.2.1 firmware with iTunes. I left my AT&T GoPhone SIM in during the restore and it activated the iPhone when the process completed. An H2O SIM will also activate the iPhone and allow you to make calls. Note: If you have edited your hosts file to redirect requests from the Apple server to the Cydia server instead, then you'll have to undo that in order to restore to stock 4.2.1 firmware.



Step 3.

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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You will now have Cydia on your SpringBoard. Here I am on 4.2.1 firmware and 03.10.01 modem firmware. Hopefully an unlock isn't too long of a wait.

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