[systemd-devel] Xorg+logind+DM issue: inactive graphical session for seat0

Zbigniew Jędrzejewski-Szmek zbyszek at in.waw.pl
Tue Oct 29 17:12:59 CET 2013

On Tue, Oct 29, 2013 at 01:44:49PM -0200, Laércio de Sousa wrote:
> Joseph Nuzman, who opened the bug above, suggests some approachs to avoid
> this problem, and I really want to know what do you think about them:
> * DMs should always set the XDG_VTNR variable for seat0. GDM currently
> doesn't set this variable, but a forked version of LightDM, maintained by
> Ubuntu Multiseat team (merging into upstream is under consideration), does
> it.
If I understand the analysis, *two* different X instances would share the
same VT. This might work, but option 4 seems superior.

> * pam_systemd should have its heuristic to infer the seat0 VT number
> improved. Maybe parsing X server /proc/<pid>/cmdline for a vtXX argument.
This looks ugly.

> * DMs should ensure that seat0 X server starts before any other one. Stefan
> Brüns has provided a similar approach for KDM on Fedora/openSUSE: it
> ensures seat0 X server starts at the same VT previously used by Plymouth.
This looks racy — let's say that at some point two users on two seats kill
their X's. It's impossible to order such events.

> I would append another approach to the list:
> * For non-seat0 seats, X server should open no VT at all. Currently, even
> with -sharevts option, it seems Xorg does open a VT, although it can't
> control this.
Right, so why not do this?


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