I suggest you install twrp and multirom, then search for multiboot ubuntu, there's a thread round here wIth a handful of precompiled linux distros. This allows you yo keep android while enjoyong running linux.
Oh and I reccomend not using unity in ubuntu iy is terrinle and keeps crashing.
I have ubuntu permanently installed but very rarely use it. Lacks hardware accelleration, which is a shame as I think nvidia o[en sourced the tegra drivers. I dod have a little go at getting them running but failed miserably!