Easy step guide to installing dual boot on your Samsung Galaxy S IV GT-I9500 Samsung Google Nexus 10 Manta Sony Xperia Z Yuga Sony Xperia ZL Odin

Everybody would like to have a dual booting system on their smart phones.  Right now you get a lot of custom ROM which you can install on your smart phones but the problem is that you lose the stock ROM in the process.  Dual booting is a process which lets you use two ROMs on your devices and lets you run the one you fancy at any given moment.  This way you are using the custom ROM as well as the stock ROM so you can get official updates also.  Isn't that good news.  Team MoDaCo is working on a similar kind of procedure which is called MoDaCo Switch.  

However a XDA Forum member Garak has successfully created a mod that allows you to dual boot ROMs on the Samsung Galaxy S IV without having to make backups or wipe your devices. Just remember, the main ROM has to be the stock TouchWiz ROM which Samsung provides but the second one can be any ROM that is based on the AOSP (Android Open Source Project) which has nearly 100s of ROMS for the taking.

Garak has warned that the Mod is experimental and only seasoned modders may use it.  If you are sure about it than you can go right ahead but be aware of this warning 

It's only for advanced users and I am not responsible if your S4 get bricked or transform into a monster and eat up your cat

- CyanogenMod

First thing you have to remember is that your first ROM will be the Samsung stock TouchWiz ROM and the second one will be of your choice.  This Mod switches between two kernels, TouchWiz can use any kernel but for ASOP you have to use Garaks modified CM Kernel.  The GraSwitcher App will download the all needed files for you. They will be in /sdcard/romswitcher.  The default kernel for TouchWiz is Perseus Kernel but if you want to change it to something else replace first.img in /sdcard/romswitcher/ with your favourite kernel.

Now download your favourite AOSP ROM and extract it.  Open META-INF/com/google/android/updater-script and look for this line

Replace mmcblk0p20 with mmcblk0p19 as in image below

Now find this lines and delete them both

After doing the above go here and download Gapps.  Extract it and open updater-script and locate the following code

And replace it with

After replacing the above code ZIP your ROM first and then ZIP Gapps.  After zipping them both Flash both of them in recovery MOD (first ROM then Gapps).  Do not repeat do not wipe out anything.  

Reboot your phone and if you did all correct. You should boot into your TouchWiz ROM.  Now download and install Garak's APK from here.  Once you have installed it open GraSwitcher and follow the instructions and you can see this screen

Thats it, now you have a dual booting system on your smart phone. If you face any problems you can post your query on this thread of the XDA Forums

Supported Devices
Samsung Galaxy S4 GT-I9500
Samsung Google Nexus 10 Manta
Sony Xperia Z Yuga
Sony Xperia ZL Odin

Check out this video tutorial before embarking on the dual boot mission :