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Update Samsung Galaxy S2 I9100G to CM 10.1 Experimental Build based on Android 4.2 Jelly Bean ROM

Only a few weeks passed by since the Android 4.2 ROM has been launched and the guys at CyanogenMod started to work on their own release of CM 10.1 custom installments for Galaxy S2 I9100G. You can use this post and learn how to successfully update your smartphone to CM10.1 Android 4.2 based ROM.

This is only a custom release based on the CM10.1 and not an official release by Samsung. This build of CM10.1 is not final and it has been built by one of the most popular developers, Codeworkx. The custom ROM contains all the Android 4.2 features and you should install it on your smartphone only if you’re looking to test it, as it still isn’t complete and that is why you will need to backup the current ROM before moving to the tutorial.

More preparation guidelines can be found below:

  • This CM10.1 Preview build based on Android 4.2 can be installed only on the Samsung Galaxy S2 with the model number I9100G. Do not attempt to flash this custom ROM on the I9100 variant as you will brick that one. Check the model version of your phone by opening the Settings menu and then ‘About phone’ section.
  • The SGS2 I9100G should be rooted and running a custom recovery image.
  • Your phone should be on the Android 4.0.3 XXLPQ ICS Firwmare –  Tutorial HERE. You can root this firmware using this guide here. Your phone needs to be running on an Official ICS Bootloader, which can only be achieved by installing an official ICS ROM. Make sure that you root the ROM as otherwise you cannot flash this new release of CM10.1.
  • It is recommended for you to create a full NANDROID backup of your current SGS2 ROM. That will provide backup in case you don’t like the new ROM or something goes wrong and the phone cannot boot the CM10.1 Jelly Bean 4.2 custom installation.
  • Backup your most important files by moving them to your smartphone’s internal SDcard or on your computer.
  • To backup your Contacts you will need to sync them with your Gmail account ( how-to guide here ).
  • Enable USB debugging option from the Developer Options menu.
  • You need to remove the ‘sim card lock’ by opening Settings, then Location and Security. In this menu you should clear / un-check the Sim Card Lock box. If it is not selected then leave it like that and continue reading this post.
  • This is a guide for advanced Android users and you should only use it for testing purposes of Android 4.2 and CyanogenMod 10.1 Preview build custom ROM.
  • Read the entire post and make sure that you don’t skip any instructions that I’ve listed in it. If you’re having problems completing the install, then you should use the comments section and ask for extra help.

Now that you know all that, move to the tutorial and flash this new custom ROM on your SGS2 smartphone.

How to flash CyanogenMod 10.1 JB 4.2 Preview Build on Samsung Galaxy S2 I9100G:

  1. Download the custom CM10.1 preview build file from HERE.
  2. Get the Gapps for Jelly Bean files from HERE. This is the file that you’ll need to flash in order to get all the required Google applications.
  3. Use the USB cable and connect your SGS2 I9100G to your PC. Transfer the custom ROM and the Gapps zip files to your device’s internal sdcard. When the files are copied you can unplug the phone from computer.
  4. Power off your smartphone and then boot it into CWM Recovery mode. Do it by pressing and holding at the same time ‘volume up’, ‘home’ and ‘power’ buttons. Release the buttons when the screen flickers.
  5. First thing that you need to select from CWM Recovery main menu is the ‘wipe data/ factory reset’  option. Confirm and this action will wipe the data from the /system partitions, that means that your applications, sms, call logs etc will be deleted. The contents stored on the internal / external sd card will not be removed.
  6. Next, select ‘install zip from SDcard’ and then, from the new menu, select ‘choose zip from sdcard’. Find the CM10.1 JB 4.2 Experimental ROM zip and confirm that you want to install it.
  7. The SGS2 I9100G might restart during the flashing process and then it will boot automatically into CWM Recovery and continue installing all the required update files. If the phone doesn’t boot then you will have to boot yourself into CWM Recovery and then repeat step 6.
  8. After the ROM is installed you will need to flash the Gapps zip also. Complete this install then return to the main menu of the custom recovery.
  9. Select ‘reboot system now’ and your SGS2 I9100G will now boot into normal mode of CM10.1 Android 4.2 ROM.
  10. Enter your Google profile details and after that you can take control over your device.
  11. The only thing you need to do, is to begin testing the custom ROM and then tell us in comments if it works as you expected it to. Also, read the note below to learn what you can do in case the phone doesn’t boot after you apply step 9.

NOTE:  If your smartphone doesn’t boot after you install the ROM, then you will have to remove its battery. Re-insert it back into its place after 5 seconds and then repeat the entire tutorial. This time you need to make sure that you’ve met all the requirements listed in the preparation guide. Eventually you should manage to install all the files correctly.

Tell us in comments if you find any errors or bugs with this new experimental build of CM10.1 Android 4.2 JB ROM.

If you don’t like this new release then you should restore your device to the previous installed ROM by using the backup you created before moving to the ‘how-to’ part of this post.