We’ve previously posted a complete guide on how to jailbreak iOS 4.2.1 on iPhone 4, 3GS or 3G using Redsn0w 0.9.6b4. Now the iPhone Dev-Team has released Redsnow 0.9.6b5 and this release is mainly targeted for iPhone 3GS or 3G users on iOS 4.2.1 or 4.1 who rely on a carrier unlock. Redsn0w 0.9.6b5 can jailbreak iOS 4.2.1 and 4.1 and update your iPhone 3GS or 3G basedband to 06.15.00 so that it can be unlocked using the newly released Ultrasn0w 1.2.

The new redsn0w 0.9.6beta5 is out.  It gives both Windows and OSX users the ability to flash the iPad 06.15 baseband on iPhone3G or iPhone3GS.  It fetches the baseband files directly from Apple for now (the only IPSW you ever point it at is the stock IPSW for the FW on your iPhone right now).  There may be a long delay while it’s doing this (their servers are getting pounded right now)

If you do flash your baseband via redsn0w, please keep it plugged into USB the whole time.  You don’t want your battery to die during the flash process!

Please be warned that:

This will update your iPhone baseband to 06.15.00. Please do this at your own risk!

1. There is however no way to downgrade back from 06.15.00 for now. And there’s no way to hide the baseband version from Apple. This will void your warranty!
2. If some future baseband comes out with a critical fix, you won’t be able to update to it if it remains down in the 05.xx sequence (then again, you wouldn’t update to it if you wanted to keep your unlock anyway).
3. Starting with FW 4.2.1 if you have 06.15 on your iPhone you won’t ever be able to restore to stock firmware (it will fail).  You’ll need to only restore to custom IPSWs (then again, if you’re unlocker you should already be doing that).

Also, like the previous version of Redsnow:

This release of Redsn0w is based on Geohotz’s Limera1n bootroom exploit which has already pwned all current iOS devices for life. The only problem now is that the jailbreak is still a tethered jailbreak, which means you will have to boot your device into jailbroken state everytime you reboot your device. The tethered or semi-tethered jailbreak condition in Redsn0w 0.9.6b4 or b5 however only applies to new devices such as iPhone 3Gs, the newly released iPhone 4, iPad, iPod touch 2G, 3G and 4G. Old devices like iPhone 3Gs with old bootrom, iPhone 3G and iPhone 2G can be jailbroken untethered right now using the latest version of Redsn0w.

Update: You can now unthetered jailbreak iOS 4.2.1 – currently limited to iPhone 4, iPad and iPod touch 4G only.

How to update your iPhone 3GS or 3G to 06.15.00 baseband and jailbreak it on iOS 4.2.1 or 4.1

Step 1: Download iOS 4.2.1 and Redsn0w 0.9.6b5.

Step 2: Update/Restore your iPhone 3GS or 3G to iOS 4.2.1 firmware using the IPSW file you just downloaded via iTunes.

Step 3: Open Redsn0w 0.9.6b5 and point it to the iOS 4.2.1 IPSW firmware file to proceed with the jailbreak.

Step 4: When you are prompted to select your options, pick Install Cydia and Install iPad baseband options and then click Next. Click Yes if it asks you for confirmation. Redsn0w will now fetch the exploitable 06.15.00 baseband from 3.2.2 firmware and will replace it the baseband in iOS 4.2.1 or 4.1.

Note: Install iPad baseband option is applicable to iPhone 3GS & 3G users only who rely on a carrier unlock.

Step 5: Now make sure your device is both OFF and PLUGGED IN to the computer before you click “Next”.

Step 6: At this stage you will need to put your iPhone in DFU mode by holding “Power” button and then while holding the “Power” button, you will now have to hold “Home” button too. Now after few seconds release “Power” button but keep holding “Home” button until installation begins.

Step 7: You will Get a Jailbroken Device on the latest iOS 4.2.1  as soon as the process ends.

Step 8: This step is only for these devices iPhone 4, 3GS (New Bootrom), iPod touch 4G,  3G, 2G, iPad. While this is tethered jailbreak and whenever you want to do anything related to jailbreak like SSH your device, or running Cydia, you must first run your device in the so called “jailbroken state” on every reboot by using “Just boot tethered right now” option.

To unlock iOS 4.2.1 on iPhone 3GS or 3G, please proceed to this page: How to Unlock iOS 4.2.1 on iPhone 3GS or 3G

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