> Command line uses startx, which is a wrapper for xinit, which uses
> ~/.xinitrc
That's sort of the impression I had, but it's good to have it
confirmed. Should I worry about the distinction between startx and
xinit?
Not really. Most of the time, startx is what you want; xinit may be useful if you're doing something like running an Xvfb or Xnest instead of a normal X session, and don't want the usual X setup.
sudo /usr/bin/X :1 -auth /var/run/lightdm/root/:1 -nolisten tcp vt8 -novtswitch
That's going to start an X server running nothing and with no way for anything else to connect to it; not very useful.
Any ideas how to run a second LightDM on a second X server?
Display managers are usually designed to support multiple sessions; that is, instead of running a separate display manager for each display, you have a single display manager which manages multiple displays.
It also appears that LightDM documentation is nonexistent.
https://answers.launchpad.net/lightdm/+question/179211 is about how to manage multiple displays; while it gives a recipe, it also notes that the only way to work this stuff out currently is to read the source code. :/
Orthogonal question: I seem to have added an XMonad session definition
for LightDM by creating files such as
/usr/share/gnome-session/sessions/xmonad.session
and
/usr/share/xsessions/xmonad-unity-session.desktop
I did this by copying some examples, and even managed to customize
them a bit my stumbling around in the dark.
Any hints where to find documentation on these files?
The session files are the same format, and are supposed to be / work the same whether used from gdm, kdm, lightdm, etc. The Xmonad on Gnome FAQ contains a sample .session file.