For debian linux users here is how to configure things : http://www.circuidipity.com/colemak-debian.html
It's already installed in debian linux so it's very easy.
setxkbmap us -variant colemak
Or just put as 2 aliases in your .bashrc file so you can easily switch to colemak and back to qwerty again just by typing asdf in a terminal.
alias asdf="setxkbmap us -variant colemak"
alias arst="setxkbmap us"
I just did Colemak lesson 1. I will do lesson 2 tomorrow.