I am so excited that I got a new personal laptop, and for the first time in my life it didn't bring Windows preinstalled (it's the new Dell XPS 13, with Ubuntu 16.04 preconfigured).

As I turned it on, I could just set the basic settings (language, locales, etc.) and I was able to encrypt my home folder, but I remember from past installations (and that's how I currently have it in my old computer) that there was a chance of encrypting the whole disk (I think in the partitioning step).

I've been reading here at SO and in Internet and I think it is not possible to do something like "reinstalling the whole Ubuntu" from factory without having to boot it from a USB, so here is my question:

Is there a way to encrypt the whole disk once Ubuntu has been installed?
Is there a workaround? Or do I have to get an image, boot it from a USB and perform as usual.

Thank you very much in advance!