The CyanogenMod team has released CM10.1 official nightly for the international version of the Samsung Galaxy S2 with model number I9100G allowing users to update their devices to Android 4.2.1 which Google has released for its Nexus device. Since the Jelly Bean ROM is in its nightly stage bugs are likely.
Galaxy S2 users who are looking to update their devices with CM10.1 Android 4.2.1 official nightly, may follow the guide below. IBTimes UK reminds its readers that it will not be held liable for any damage to the device. Users are advised to verify the model number of the devices before proceeding since the CM10.1 nightly works only with Samsung Galaxy S2 I9100G not with any other variants. Flashing incorrect ROM may brick the device.
1) Download and install USB Drivers for Samsung Galaxy S2 in your computer.
2) Enable the USB Debugging mode.
3) Create backup of all your important data.
4) Ensure the device is rooted and ClockworkMod (CWM) recovery is installed.
5) Ensure the battery of the device is charged above 80 per cent.
Steps to install CM10.1 Android 4.2.1 official nightly on Galaxy S2 I9100G
2) Download Google Apps package
3) Connect the phone to the computer using USB cable and copy both the downloaded zip files to the SD card of your device
4) Unplug the USB cable from the phone and turn it off
5) Boot into CWM recovery
6) In CWM recovery, perform a full data wipe. Wait for some time until the data wiping task is completed, then head over to the recovery menu once the action is completed
7) Then scroll down to 'Flash zip from SD card' using the Power button. Now select 'Choose zip from SD card' by pressing the Power button again and locate the Jelly Bean ROM zip file which you have copied to the SD card. Select it and confirm installation on the next screen
8) After the ROM is installed, follow the same procedure to install Google Apps package
9) Once the installation process is completed, return to the main recovery menu and select 'Reboot System now' in order to reboot the device and boot up into the customised Jelly Bean ROM. The device will take a few minutes to boot
CM10.1 official nightly based on Android 4.2.1 is now installed and running on your Samsung Galaxy S2 I9100G. Browse Settings>> About Phone to verify the software running on your device.
[Source: XDA developer]