Good news for developers who always wanted to try out dual-booting with your Android devices. Ubuntu developers have released Ubuntu Dual Boot Installer as a tech preview for those who wish to run Ubuntu and Android on a single device. You can try this out if you’re familiar with flashing custom roms, kernels, recovery, and able to re-flash just in case your device gets soft bricked.
So what can you expect from this installation? Simple, you will be able to use two OS on a single device. Nothing more or nothing less, as mentioned above it is just a preview for those who really eager to try out Ubuntu without having to fully flash over and without having to get rid of Android OS completely. 
To get this installed you need one of these devices- Nexus 7(2012),Galaxy Nexus,Nexus 4,Nexus 10 ), with Android 4.2 or higher with Android 4.4 requires to perform few additional steps in order to make the dual boot work flawlessly. Make sure you have 2.7GB of free storage space and make sure you have ADB tools installed and running on your computer. Lastly, your device’s bootloader needs to be unlocked with the USB debugging enabled which most of us would have our device in that stage already.
For a better step by step guide on how to get this Dual Boot installer, head over to Ubuntu DualBoot .