To be familiar (and expert) with command-line of linux, Beginner is
recommended to read/visit book: The Linux Command Line. Pdf version is also
available!
Note: “graphical user interfaces make easy tasks easy, while command line
interfaces make difficult tasks possible”
And I think Trisquel (GNU/Linux) is perfect OS which is based on Ubuntu LTS
with only free software (Best GNOME based Desktop environment and most of
GNU/GNOME Applications) So, common technical wiki/tutorial for Debian/Ubuntu
can also useful here.
You can show screen-shot of free distro @ GNU which recommends Trisquel
