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[Guide]Dual boot Jelly Bean and ICS ROMs in Galaxy S2 GT-i9100

Looking to dual-boot Jelly Bean and ICS custom ROMs on your Galaxy S2 GT-i9100?
Well, the  for  Siyah Kernel i9100 supports Jelly Bean and ICS custom ROMs, just tested working flawless!
This guide is just a quick how-to on dual booting. Many people have doubts on how to dual boot on Siyah, because it's something new and perhaps "scary" because they may think it can brick their phone.


  • A Galaxy S II I9100
  • 3.x Siyah Kernel (3.2.x preferred). For latest version, visit the Siyah Kernel thread
  • 90% charged battery
  • 2.5GB of free space in your internal SD card
  • Patience
  • Time

So, do you complete all those requirements? Time to go to action. BUT BEFORE, a brief FAQ in a simplified way, based from this post made by the amazing droidphile


Can I dual boot Ice Cream Sandwich and Jelly Bean?
Yes you can, using Siyah v3.5.2.

1) What is dual booting?
Dual booting is the ability to boot into two different Ice Cream Sandwich-based ROMs (like CM9 and AOKP).

2) How is this done?
This is achieved by sharing the kernel and using a hidden partition in dev/block to store the 2nd ROM's /system and the /sdcard (Internal storage) to store /data and /cache inside a hidden folder (/sdcard/.secondrom)

3) How much does it take to clone a ROM?
It should take around 7 minutes

4) I want to dual boot fasturr. wat do?
When you get the splash screen to choose between ROMs, touch the screen or press volume UP to enter the PRIMARY ROM, and press the Home button or volume down for the SECONDARY ROM.

5) How can I remove the Dual boot and its partitions?
Just use the "Remove 2nd ROM" option in the Dual Boot options menu.

6) If I format my /sdcard, will my second ROM go kaput?
Yep, because you're wiping the folder that contains /data and /cache.

7) Can I dual boot a gingerbread ROM in a ICS ROM?
Niet. No.

  1. You must flash the Siyah kernel, either with CWM or ODIN
  2. After you have flashed the kernel, reboot and let Android upgrade itself.
  3. All done? Alright, move up to next step!
  4. Download the desired ROM that you want to make it secondary, and place it in a safe place in your internal SD card
  5. After that, reboot to CWM Recovery, and navigate to "Dual Boot options"
  6. You'll see a list of options, namely :
    • View current status
    • Clone 1st ROM to 2nd ROM
    • Clone 2nd ROM to 1st ROM
    • Swap 1st ROM with 2nd ROM
    • Swap 2nd ROM with 1st ROM
    • Remove 2nd ROM
    • Install 2nd ROM from Internal SD card
    • Install 2nd ROM from External SD card
    • Wipe 2nd ROM data/cache
    • Wipe 2nd ROM dalvik-cache
    • Fix 2nd ROM permissions

      What does each one mean, you ask?
      • View current status - This option will show you the stats of the dual booted ROM.
      • Clone 1st ROM to 2nd ROM - This option will copy (clone) the current ROM that you use (for example, CM9) and paste it to the 2nd ROM directory. Takes around 7-20 mins.
      • Clone 2nd ROM to 1st ROM - This options copies the 2nd ROM (after installed of course) and pastes it to the place where the 1st ROM was, replacing it.
      • Swap 1st ROM with 2nd ROM - This will swap the 1st ROM with the 2nd ROM, making the Primary ROM -> Secondary ROM and the Secondary ROM -> Primary
      • Swap 2nd ROM with 1st ROM - This will do the exact opposite of the above option
      • Remove 2nd ROM - This will completely wipe and remove any 2nd ROM files and folders
      • Install 2nd ROM from Internal SD card - This option is to flash the ROM to the 2nd ROM directory from the Internal SD card
      • Install 2nd ROM from External SD card - This option is to flash the ROM to the 2nd ROm directory from the External SD card
      • Wipe 2nd ROM data/cache - This will wipe the 2nd ROM data and cache. When it's done for the first time, it'll create data.img and cache.img and create the folders inside /sdcard/.secondrom, preparing your phone for the 2nd ROM.
      • Wipe 2nd ROM dalvik-cache - This will wipe the dalvik cache of the 2nd ROM
      • Fix 2nd ROM permissions - This will fix the permissions of the 2nd ROM
  7. Select the option Wipe 2nd ROM data/cache. This will prepare your phone to flash the 2nd ROM. It takes around 5-7 minutes.
  8. After having that done, select the option to wipe the dalvik cache.
  9. After all that is done, select either "Install 2nd ROM from Internal SD card" or "Install 2nd ROM from External SD card" depending on the location of your ROM
  10. Wait a few minutes for the flash
  11. Reboot
  12. Press the Home button or volume down to enter the Secondary ROM

After you have done all that, you're set and you're in the Dual Booting world! I hope that this guide helped you, and if it did, press the thanks button!


GokhanMoral - For his amazing kernel
Droidphile - For his great FAQ

 Siyah Kernel S2-v5.0.1 Changelog:
  • Dual booting with new CM10 + Samsung ICS ROM
  • improved touch sensitivity
  • 5-step GPU
  • added arm topology patches again, with cpupower driver.
  • merged with a JB leak (3.0.31)
  • removed dynamic cpu freq steps. they are all fixed now.
  • removed some settings from ExTweaks interface such as cfstweaks
  • orbot is now working (only tested on Samsung ROM)
  • Reboot into 1stROM, Reboot into 2ndROM in STweaks. (v5.0a2)
  • STweaks added to initramfs. it will be autoinstalled only once. it is my own implementation of interface. There is almost no difference (except for resetting to defaults in the last tab) between ExTweaks and STweaks. It’s been used for some time in my S3 kernel and fairly stable. I wanted to put it in the last version of my S2 kernel as well. it is my second android app (first one is FastDormancy app).. it doesn’t have a fancy UI but not bad for a beginner :) .
  • BLNWW (BLN Without Wakelock).
  • Touch gestures optimizations (thanks to Tungstwenty for the latest changes and for this great feature).
  • added speaker and mic amplification/sensitivity settings which are based on fluxi’s mc1n2 interface, reversed and ported to interface by dorimanx, tested and committed to my initramfs by robertobsc.
  • automatic led brightness level. touch voltage level will be ignored if this one is checked in STweaks
  • added B2G support (thanks to atilag@github for the initramfs changes).
  • added an option in STweaks to set a delay in FB earlysuspend to properly play CRT animation (implemented originally by Codeworkx).
  • reverted wifi driver to the one in cm10 kernel
  • fixed auto-brightness issue on CM10.
  • fixed some 2ndROM related problems in recovery when installing zips or restoring backups
  • fixed BLN intensity when auto led brightness is selected.
  • applied latest lulzactiveq tweaks from robertobsc.
  • mali and vsync related changes (mostly from Entropy512′s commits) which are supposed to improve the battery life
  • removed battery and performance profiles.
  • removed lots of cpu governors. available governors: pegasusq, ondemand, conservative, hotplug, lulzactiveq
  • new optional GPU frequency steps. enable VPLL Mode in STweaks but make sure you read the description.
  • fixed a CM10 specific problem with the new GPU steps but it still doesn’t guarantee that the new steps will be stable on your device.
  • added slide2wake (thanks to Fluxi) + some optimizations
  • added mdnie interface and made hardcore’s sharpness tweaks optional in STweaks
  • lulzactiveq fixes by robertobsc and added cpu governor selection back to stweaks
  • Finally fixed vpll problem and made it default (thanks to robertobsc for his helps on testing)
  • v5.0i -> v5.0.1: reverted wifi driver to fix wifi direct & other wifi related problems. touch gestures off when screen is off. analogue headphone amp in stweaks. new & faster stweaks. mxt224e touchscreen choppiness fix.
 SiyahKernel S2-v5.0.1:DOWNLOAD TAR (for Odin)
DOWNLOAD ZIP (for CWM Recovery)
Download Siyah Kernel v.4.0.1 ZIP for CWM
Download Siyah Kernel v.4.0.1 TAR for ODIN

source: XDA and
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