In ancient times, an X11 session was somehow started with xinit and ran through /etc/X11/Xsession and its startup files. At least in 16.04, but I think even earlier, this is not true anymore, as I found by putting some file creation into /etc/X11/Xsession that was never called.
Is anyone able to explain the sequence of events that happens when I log into the machine from a lightdm greeter, maybe in particular with Xfce4 as the window manager, but possibly with others. Which processes are started, which scripts are run? A rough starting point would even suffice, since I could dig into it from there.
