Android 5.1 Lollipop
update Galaxy S2 I9100 and Galaxy S I9000 to Android 5.1 Lollipop via OmniROM XDA

Galaxy S2 I9100 and S I9000 are among the lucky few Android devices to receive the first ever Android 5.1 Lollipop update, with due credit to the release of OmniROM from third-party Android developers.

The OmniROM offers the best Lollipop features taken from top Android custom ROMs such as CyanogenMod, SlimROMs and ParanoidAndroid ROM. It is based on the original Android Open Source Project (AOSP), which brings the closest stock Lollipop experience just as in Google Nexus devices.

Those who wish to experience the latest Lollipop features on their ageing Galaxy S2 can go ahead and install the Android 5.1 based OmniROM on their device, using the step-by-step guide posted below.

IBTimes UK reminds readers that it will not be held liable for any damage to device during or after the ROM installation. Users are advised to proceed at their own risk.


  • The instructions given in this guide are meant for the international variants of Galaxy S2 and Galaxy S with model numbers GT-I9100 and GT-I9000 only. Verify device model number by navigating to Settings > About Phone
  • Ensure the phone has at least 80% battery charge to prevent unexpected device shutdown (due to battery drain) while installing the ROM
  • Back up data and settings using a recommended custom recovery tool, like ClockworkMod (CWM) or TWRP, as it creates a complete image of the existing phone setup. In Recovery, choose Backup and Restore and tap Backup
  • Verify correct USB drivers for the phone are installed on the computer (download USB drivers for Galaxy S2 or Galaxy S I9000)
  • Enable USB Debugging mode via Settings > Developer Options (if running Android 4.0 or above) or Settings > Applications > Development (if running Android 2.3 or earlier)
  • Ensure that the device is rooted with CWM recovery installed and its bootloader is unlocked

Downloads Required

Android 5.1 OmniROM for Galaxy S2 (GT-I9100)

Android 5.1 OmniROM for Galaxy S I9000

Google Apps for Android 5.1 Lollipop

Steps to Install Android 5.1 OmniROM on Galaxy S2 GT-I9100 and Galaxy S GT-I9000

Step 1 - Download OmniROM Android 5.1 custom ROM for Galaxy S2 or Galaxy S I9000 on the computer.

Step 2 - Connect and mount the phone's USB mass storage on computer with the USB cable.

Step 3 - Now, copy the downloaded OmniROM zip file to the root folder on the phone's SD card.

Step 4 - Power off the phone and disconnect its USB cable from computer.

Step 5 - Now boot the device into Recovery Mode by pressing and holding Volume Up, Home and Power buttons together.

Step 6 - Once the phone enters into CWM Recovery, perform a full data wipe task by clicking Wipe Data/Factory Reset. Use the Volumekeys to navigate between options and the Power button to select an option in the Recovery Mode.

Step 7 - Then, perform Wipe Cache Partition and wait until the process completes.

Step 8 - Now perform Wipe Dalvik Cache as well. To do this, go to the 'advanced' option and then click Wipe Dalvik Cache. This will help in preventing boot loop issues or any boot ROM related errors during firmware installation.

Step 9 - Then return to the main recovery menu and choose Install Zip from SD card.

Step 10 - Now click Choose Zip from SD card. Use volume keys to navigate to the OmniROM zip file that you copied earlier to your phone's SD card and choose it by tapping the Power button. Confirm the ROM installation on the next screen and the installation process will begin.

Note: Repeat Step 9 and Step 10 to install Google Apps (Gapps) as well.

Step 11 - Once the ROM and Gapps installation completes, go to "+++++Go Back+++++" and select Reboot System Now in the Recovery menu.

The phone will now reboot and the first boot may take about five minutes to complete. So, please be patient.

Your Galaxy S2 I9100 or Galaxy S I9000 is now running the latest Android 5.1 Lollipop update via OmniROM custom ROM. Go to Settings > About phone to verify the firmware version installed.

[Source: Team Android – Galaxy S2 I9100 / Galaxy S I9000]