How To: Use CyanogenMod 12.1 To Install Android 5.1.1 Lollipop On Samsung’s Galaxy S2 I9100

When the Samsung’s Galaxy S2 I9100 was released to the market on February 2011, it was a huge hit.  It is still considered one of the best smartphones of all time.

While the Galaxy S2 is still a good device, it is also an old device, at least four years old by now.  Because of this, there is no official support or updates for this device from Samsung.  The last official update the Galaxy S2 received was to Android 4.1.2 Jelly Bean.

Die-hard Galaxy S2 fans have been getting around the lack of official updates by using custom ROMs.  To update a Galaxy S2 to Android 5.1.1 Lollipop, we recommend you use the CyanogenMod 12.1 for Samsung’s Galaxy S2 I9100.

The CM12.1 gives your device the features of Android Lollipop and brings some improvements to device speed and battery performance.  In this post, were going to show you how you can install this rom on a Galaxy S2 I900.

Prepare your device:

  1. This guide and the ROM we are going to be installing are only for a Galaxy S2 I900. Do not use this with another device
  2. Charge the device’s battery to at least over 60 percent.
  3. Unlock the device’s bootloader.
  4. Have a custom recovery installed. Afterwards, use it to make a backup nandroid.
  5. You need to use Fastboot commands to install this ROM. Fastboot commands only work with a rooted device.  If you are not yet rooted, root your device before proceeding with ROM installation.
  6. After rooting your device, use Titanium Backup
  7. Backup SMS messages, call logs, and contacts.
  8. Backup any important media content.


Note: The methods needed to flash CyanogenMod 12.1, roms and to root your phone can result in bricking your Samsung’s Galaxy S2 I9100.  Rooting your device will also void the warranty and it will no longer be eligible for free device services from manufacturers or warranty providers.  Be responsible and keep these in mind before you decide to proceed on your own responsibility.  In case a mishap occurs, we or the device manufacturers should never be held responsible.


CyanogenMod 12.1: Link

Gapps: Link | Mirror


  1. Connect your device to the PC. You should use the PC with which you downloaded the two files above on.
  2. Copy and paste the two files you downloaded to the root of your device’s SD card.
  3. Open your device into recovery mode:
    1. Your device needs to be connected to the PC.
    2. Open a command prompt in the Fastboot folder.
    3. In the command prompt, type: adb reboot bootloader.
    4. From Bootloader, choose Recovery.
  4. Depending on what recovery you have on your device, follow one of the guides below.

For CWM/PhilZ Touch Recovery:

  1. First, use Recovery to make a backup of your current ROM. To do so, go to Back-up and Restore and choose Back-up.
  2. Return to the main screen.
  3. Go to advance and choose Dalvik wipe cache
  4. Go to Install zip from SD Card. Another window will open.
  5. Choose wipe data/factory reset.
  6. Choose zip from SD card.
  7. Select the file first.
  8. Confirm you want the file installed.
  9. Repeat these steps for the
  10. When installation is finished, choose +++++Go Back+++++
  11. Now, select Reboot now.


  1. Tap the Backup option.
  2. Select System and Data then swipe the confirmation slider.
  3. Tap Wipe Button.
  4. Choose Cache, System, and Data. Swipe confirmation slider.
  5. Return to the main menu.
  6. Tap install button.
  7. Find the and the
  8. Swipe confirmation slider to install both files.
  9. When the files are flashed, you will be prompted to reboot your system. Select Reboot Now.

Have you installed this CyanogenMod 12.1 on your Samsung’s Galaxy S2 I9100?

Share your experience in the comments box below.


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