CyanogenMod 12.1 for Samsung Galaxy S2G - I9100G - CM12.1 - Android 5.1.1 - cm-12.1 - ROM


CyanogenMod is a free, community built, aftermarket firmware distribution of Android 5.0.1 Lollipop, which is designed to increase performance and reliability over stock Android for your device.

This is an UNOFFICIAL build of Cyanogenmod CM 12.1 for Samsung Galaxy S2 G (I9100G). It's build from sources on & xdaamg. Standard functionality is working, when you follow flash instructions. Android 5.1.1 is running smooth on this device.



By flashing a custom rom, your warranty is void.
I am not responsible for bricked devices, dead SD cards and so on. You are choosing to make these modifications.
I will not give support for modifications and apps you install/flash.
Confirmations of working things are welcome. If you found a bug, provide a logcat of it


First time installation instructions:

  • Backup your media files on internal memory (photos etc.)
  • Download cm-12.1 i9100g ROM and OpenGApps (ARM, Android 5.1, Nano) to your sdcard. Use open gapps dated with 20150821 for first time setup!
  • Boot into Recovery. If you don't have TWRP first flash TWRP and reboot into recovery.
  • Wipe data (system, data, cache, dalvik, internal)
  • Flash cm-12.1 rom and OpenGApps Nano 20150821
  • Reboot system and follow instructions in setup wizard. After finishing all, reboot again 


Updating ROM: 

  • Download I9100G CM-12.1 ROM to your sdcard/internal
  • Boot into recovery
  • Flash ROM
  • Reboot System


Download I9100G CM12.1 ROM UNOFFICIAL:

Download CM12.1 I9100G ROM


Download Google Apps:

Open GApps (recommended: Download OpenGApps 20150821)



If you find this rom useful and want to support me, consider donating. I will do my best to continue building roms for this device.


Forum (Developer Thread, FAQ):

XDA-Developers I9100G CM12.1 Thread


Changelog CyanogenMod 12.1:

CM12.1 changes



Android-Version: 5.1.1
CyanogenMod-Version: 12.1
Security patch level: 01.11.2016
Kernel-Version: 3.0.31
SELinux-Status: Strikt


Standard functionalities are working. No known major errors or force closes. It's good for daily use.

Tested functions: Telefon, sms, wifi, data 2g/3g, camera, 3d-grafics, sensors, gps, compass, vpn, wifi hotspot, screencast, speaker, playstore.


Special features:

- TWRP IsoRec: Booting TWRP from recovery partition

- F2FS: Flash-friendly file system supported on sdcard, internal, cache

- good standby times

- responsive, smooth gui

- last i9100g cm-12.1 rom which still gets updates


CM12.1 changes




Additional informations:

  • Root is integrated but disabled by default on CM12.1. To enable it, activate developer options and then go to Settings>Developer Options>Root access and set to Apps only or Apps and ADB. 
  • CyanogenMod 12.1 comes with Cyanogen Recovery by default. But this rom supports booting isorec twrp recovery. Flash twrp isorec recovery to recovery partition. rom will use then twrp as prefered recovery. Follow flash instructions for i9100g isorec twrp recovery in XDA developers i9100g cm-13.0 thread (post nr. 2)
  • GApps: For first time setup use OpenGApps from 20150821. Newer versions could lead to problems with not working google play services.
  • About battery: Display and data connections/syncing use most energy. I suggest to reduce display brightness and switch off adaptive brightness. Also switch off background data connections/syncing for apps you don't use or which will be updated when you really use it
  • After first flash give phone some extra time to complete all tasks, even when it's reacting already to your inputs, it's working hard. Wait some minutes. It's also a good idea to do another reboot after some time. This solved some problems in the past.
  • If you are experiencing force closes try first to clean cache/dalvik cache with recovery. If it's still not working, go to settings/apps, find the offending app and clear data. Still not the solution? Then do a clean flash with factory reset.


Known (minor) problems:

  • Activating flashlight with quicksetting-icon (-> use another flashlight app and (optionally) replace lockscreen app for quick access)
  • Manual selection of phone network (-> use automatic network selection)


TWRP Recovery for updating cm12.1 older than 20151207:

Download TWRP Recovery signed ZIP