Starting ctwm on ubuntu

For those of you who want to use ctwm window manager on ubuntu.

I installed ctwm and was surprised that it did not show up among other sessions in the login screen of gdm.
With a little research I found that all you have to do is:

1. cd /usr/share/xsessions
2. copy one of those existing_session.desktop files I’ve chosen Fvwm.desktop: cp Fvwm.desktop ctwm.desktop
3. edit this new file, exchanging Fvwm with ctwm everywhere: sudo vi ctwm.desktop
4. restart and enjoy ctwm