I have a copy of Debian Gnome, installed from live medium then upgraded to testing. I've decided to change my default X environment from GDM to i3 for reasons of productivity. This lead me to wanting to change my default runlevel from 5 to 3, and then configure runlevel 3 to run i3, in the event that I wanted to run GNOME3 again for whatever reason.
I haven't quite figured out how to do this. Systemd manuals reccommend changing
graphical.target to something else. So I searched through systemd folders for a file named
graphical.target, so that I could configure my own custom target, say,
i3.target, but I couldn't find it. So then I found that in Debian, a large portion of Systemd's startup scripts are actually just called from /etc/init.d as sysvinit scripts. And some Upstart scripts are called too. But now I have no idea what
graphical.target calls, so I can't create a custom startup script to launch i3.
So, I think my question is as to how to create a custom target in Systemd. But it's a bit more general than that, I'm pretty confused on the whole Systemd/Sysvinit/Upstart situation as a whole.