(06-09-2020, 04:34 PM)octahedral Wrote: Does this mean that display managers are doing the same thing behind the scenes without calling xinit?

Display managers do quite a lot more, like managing sessions login (consolekit/login1/etc), seats (useful in a multiseat system, I haven't actually encountered any real use for this, I don't know of any software using login1 to query the seat and use that value), checking if they are running inside X already to use Xephyr as the Xserver (not sure if this has any usage either), they can connect to remote X servers, they may communicate with the Xserver using XDMCP (X Display Manager Control Protocol) if an XDMCP server is running and configured (not usually by default on user machines, also maybe only useful in Citrix-like/remote-desktop environment and mostly deprecated), or via VNC aka running with Xvnc (also not usually by default on user machines), they can have a nice UI to login along with a plymouth (on Linux) splashscreen/bootsplash, set the xsession environment related stuff (like startx and others), etc.
I think maybe TeamViewer actually uses the remote desktop features of display managers, probably vnc. I ran wireshark but there's a wireguard VPN session going on, so I can't know what's actually happening, and ss doesn't show the display manager listening either. Filtering by "vnc || xdmcp || x11" on any interfaces shows nada, but it's definitely UDP packets as I can see the IP of the other machine. Maybe someone can correct me on this, it's probably doing something on the unix-socket level or dbus. EDIT: Actually, I've found that it uses multiseat feature of the displaymanager, SeatNew and others are emitted by /org/freedesktop/login1 bus, so that's it.

But basically, when it's local, which is the case 99% of the time today, it does the same as xinit but with the advantage of handling the login and having a nice UI, see lightdm for example.



Also, display managers aren't limited to X11, they can support Wayland sessions too.