Control Linux from afar

X-WindowsWhen you have one computer under GNU/Linux, it is common to have it as a second machine to run experimentations or dedicated to one single task (run one program like BitTorrent, a backup server or a web server, for example). In this case, it is quite pleasant to be able to control it without leaving your main keyboard and screen (staying in front of your main machine). This is the problem that some bloggers tried to solve and I want to cite them here: