Update Galaxy S2 i9100 to Android 5.0 Lollipop CM 12. The last official firmware released for Galaxy S2 was Android 4.1 Jelly Bean after which Samsung stopped working for this device. However, because of the third party Android developers the Galaxy S2 i9100 was able to receive custom firmware based on Google’s latest mobile operating system. After Google rolled out the new Android 5.0 Lollipop OS, many Android users were waiting for this update to be rolled out for their phones. But only a few lucky ones got a chance to experience this latest firmware officially. The others had to rely upon the custom ROMs based on this firmware. You might know the famous and most used community of developers called Cyanogenmod. These CM developers with their hard work have recently developed CM 12 ROM based on the latest Android 5.0 Lollipop OS. Yeah you heard it right. Android L for Galaxy S2! Isn’t it amazing? All credit goes to members of the CM community.

Also Read: Install Android 8.0 Oreo based  Lineage OS 15 ROM on Galaxy S2 i9100. (LATEST)

Also Read: Install Android 6.0 Marshmallow based Cyanogenmod 13 ROM on Galaxy S2 I9100.

Samsung Galaxy S2 i9100 had no chance to get this latest update officially but thanks to the CM team who made this dream come true. This CM 12 ROM based on Android L has all the advanced Lollipop flavored features including CPU Governor, refurnished home screen, new dialer app, new themes, theme editing, personalization and standard memory, new services, low memory management support, new gallery, new keyboard, new customization, battery saving tweaks & much more. As this device is much compatible with Android 5.0 Lollipop it can smoothly run these features. Along with that it brings optimized RAM, updated Linux kernel and enhanced processing function.

But unfortunately, this build is in its initial stage, hence you may face some untested bugs and issues. But don’t worry as this ROM is build by the well known CM team, all the bugs and issues will definitely be cleared when a new update is released. If you want to try out the Lollipop on your Samsung Galaxy S2 i9100 then proceed to our actual article given below.

Galaxy S2 i9100 Android 5.0 Lollipop CM 12 screenshot 1Galaxy S2 i9100 Android 5.0 Lollipop CM 12 screenshot 2


We will not be held responsible for any damage caused to your galaxy S2 i9100 by using this guide. This article is made in a detailed step by step manner so perform each and every step with an attentive mind. Don’t make any decision of your own. Although I assure you that if you follow everything given below correctly without a single mistake then no damage will be caused to your phone.


All the steps given below must be implemented only on international variant of Samsung Galaxy S2 bearing model number GT-I9100. Don’t even think to flashing this CM 12 ROM on any other device or variant. If tries your  device may turn into semi bricked / non functioning state. If you are unsure of your device’s model number then first check it before performing these steps. You can check your device’s model number from Menu–>Settings–>About phone.

  • Better check your battery power before proceeding further. Lack of battery can interrupt the process thus increasing further problems. So ensure that you’ve charged your device at least up to 60%.
  • Your phone data will be lost after flashing this CM 12 ROM. Therefore, it is highly recommended to backup all your data from internal storage. For the safe side, you can transfer all the data on PC or your phones external SD card. Backup may include contacts, messages, call logs, apn settings, memos etc.
  • You might be knowing that a folder called EFS present in your phones system directory contains all your phones specific information such as the IMEI, wireless devices MAC addresses, product code, and much more. If by mistake this folder gets wiped out then your device will be completely useless & will no longer be recognized by your carrier. Refer our article to backup and restore EFS/IMEI data:
  1. How to backup and restore EFS/IMEI on Android Phones.
  • Your Samsung Galaxy S2 i9100 must be Rooted.
  • Make sure you have installed mobile specific drivers on your PC. This is important so to recognize your phone when connected via USB cable. You can install them by installing Samsung Kies or manually install them from the link given below:
  1. Download latest Samsung USB Drivers.
  • Make sure you have installed latest custom recovery like Clockworkmod (CWM) or TWRP before flashing this CM 12 ROM. If not, then don’t worry just follow the steps given below:

Step 1: Download and copy this CWM recovery on your phones external SD card.

Step 2: Switch off your Galaxy S2 i9100 completely and boot into recovery mode.

Step 3: Recovery mode can be entered by simultaneously pressing & holding Volume up + Home button (middle button) + Power button.

Step 4: Using Volume keys navigate to the install zip from SD card’ option followed by ‘choose zip from SD card’ option and then select this CWM recovery using Home button.

Step 5: After successfully flashing it, return to the main menu and select reboot system now option to restart your Galaxy S2 i9100.

That’s it! You’ve flashed the latest CWM recovery. Now install the actual Android 5.0 Lollipop ROM.

Galaxy S2 i9100 Android 5.0 Lollipop CM 12 ROM

Procedure to install Android 5.0 Lollipop on Galaxy S2 i9100 [CM 12]:


  1. Download Cyanogenmod 12 Custom ROM for Samsung Galaxy S2 i9100.
  1. Download Google Apps (Android 5.0 Lollipop).


Step 1: Download both package files in a folder on your PC. Do not extract them.

Step 2: Now using USB cable connect your Galaxy S2 i9100 to PC and transfer both the downloaded files on your phones SD card.

Step 3: Disconnect the phone from PC & switch it of f completely. Enter your phone into CWM recovery mode now. Recovery mode can be entered by pressing & holding Volume up + Home button (middle button) + Power button together till you enter recovery mode.

Note: Touch won’t work in recovery mode. So use Volume keys for navigating up and down and use Home button for selection.

Before flashing any custom ROM it is necessary to backup your current ROM. The same can be done using nandroid backup. This nandroid backup is the backup of your entire operating system & is always helpful during the failure while flashing process or during any problem with the ROM, then you can easily restore your saved previous ROM.

Refer our detailed article for taking Nandroid backup:

  1. How to take Nandroid Backup of any Android Phone with 8 simple methods.

Step 4: For doing so, navigate to the ‘backup & restore’ option on the recovery mode itself and on the next screen select ‘backup’ option. This will make a complete nandroid backup of your current ROM. Refer screenshots.

Nandroid backup screenshot 1Nandroid backup screenshot 2

Step 5: Now clear the data/cache present on your phone. For that navigate to the ‘wipe data/factory reset’ option and on the next screen select ‘wipe cache partition’ option. This will clear all the data & caches from your phones internal memory respectively. So a complete backup of everything is must before attempting this step (refer prerequisites).

CWM wipe data cache screenshot

Step 6: Now navigate to the Advanced option located on the recovery mode itself. Select Reboot Recovery  option on the next page.

reboot recovery screenshot

Wait until you boot again into recovery.

Let’s move to the actual Android 5.0 Lollipop based CM 12 ROM flashing process.

Step 7: Go to the ‘install zip from SD card’ option using Volume up and down keys & select it using Home button. Then on the next screen select ‘choose zip from SD card’ option. As soon as you select this option, it will show all the files and folders present on your external SD card. Just search for the CM 12 ROM which you’ve copied earlier and select it. On the next page select ‘Yes’ option to start the actual Android 5.0 Lollipop flashing process. It will take some time to complete successfully. So wait and be patient.

CWM recovery Screenshot

Step 8: After completing the process again select ‘wipe data/factory reset’ option and ‘wipe cache partition’ option on the recovery mode to clear all your phones data & cache. This step is essential to solve the boot loop issue.

Step 9: Similarly flash the Google Apps (GApps) as you’ve flashed this Cyanogenmod 12 custom ROM. Just remember not to wipe data/cache after flashing them.

Step 10: Restart your Galaxy S2 i9100 by selecting ‘reboot system now’ option from the recovery mode. This first boot will take more time to start than usual. But don’t panic after a couple of boots it’ll be normal.

reboot system screenshot

Note: If you want to restore back your previous Rom, then you can do that by going back to the recovery mode by pressing & holding Home Button (middle button) +  Power Button simultaneously and select ‘Backup and Restore’ option and then on next page select ‘Restore’ option. Select the ROM you want to restore.


Gotcha! Android 5.0 Lollipop based Cyanogenmod 12 Custom ROM has been successfully flashed on your Samsung Galaxy S2 i9100. You can verify the same from Menu->Settings->About Phone. If you’ve any queries or need help regarding the procedure that we’ve mentioned, feel free to ask us in comments below & we’ll be more than happy to help you. Till then Enjoy! 🙂

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