Multiple sessions on a single seat

[Diego Alvarez]

I upgraded LightDM and I'm having some trouble replication my old config.
What I want to do is, when booting, have multiple sessions running at on different VTs on a single seat. I mean, only one monitor/keyboard but have one user logged in on VT7 and another user on VT8 using another DE and such.
This was possible on older versions of LightDM, before integrating logind's seat detection. I just used the [Seat:x] configuration in /etc/lightdm/lightdm.conf and it did exactly what I wanted.
Problem is that now LightDM uses logind to handle detecting the seats, but it seems to ignore the fact one may want to run multiple sessions with one seat only. Configuration for the first session works fine, but I can no longer tell LightDM to start other X sessions on another VT.
I can use 'dm-tool' to start another session, but I cannot make it so LightDM does that automatically on startup nor configure the new session (i.e. autologin, which greeter to use, etc).

Was support for this officially removed or is it just not implemented yet, after the logind integration?

Edit: I just found https://bugs.launchpad.net/lightdm/+bug/1171680 which is very related to this, but old and probably not yet aware of logind.

[Robert Ancell (robert-ancell)]

Multiple sessions on one seat was never intended to work, so this is not an implemented feature.

[Bernd Wechner (thumbone)]

I'm puzzled that this is so mildly a wishlist item. It would seem a fairly simple and commonly desired use case. For example we have a machine at home for family use and wow it would be so nice if I could run a greeter session on numerous virtual terminals and I teach family members to flick to theirs to their stuff. But more to the point I want to use two as I find others have expressed a desire for. I'd like to be doing my dev work on one VT while I do other stuff on other. Why? Well I get tired of something locking up my DE somehow and then I have to log out and log in losing my whole session, to fix it. I'd like to be doing heavy risky stuff (web browsing, media etc) on one session while I can flick to my dev TTY and save everything cleanly if I need to reboot, or not even have to reboot, just killed the other session and log in to it again.

In short multiple sessions exploits the power of Linux VTs and is already fully supported on tty1-6 with console logins. As if I ever needed six of them! But I do often sue tty1 to log on and try to fix session issue son tty7 ...

Further, it can't be hard to do. Because Switch User already does it opening a greeter on tty8 and locking the original session on tty7. All we're asking is that it's easy to configure greeters to run on tty8, and up as desired where you can log a session in, without locking the other one(s).

See:

https://github.com/canonical/lightdm/issues/40

and:

https://askubuntu.com/questions/1070368/lightdm-whats-the-difference-between-a-seat-and-a-session

where some of this is discussed too.