Bug#935194: xfce4-session: Xfce session fails to start when previously logged into GNOME

[Yves-Alexis Perez]

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On Wed, 2019-08-21 at 15:43 +0200, Ronny Standtke wrote:
> > I have no idea why SESSION_MANAGER is already set when you start Xfce
> > the second time, but it looks like a bug in either gdm or gnome.
> 
> As I said, the variable SESSION_MANAGER will be set when you log into
> GNOME (or GNOMEish desktop environments like Cinnamon or MATE). The
> variable is added to the systemd manager environment block. You can
> verify this by calling
> 
> systemctl --user show-environment | grep SESSION_MANAGER

I don't use GNOME and am not at all knowledgeable in systemctl “user” session.
In any case, that commands reports nothing in my Xfce session.
> 
> The systemd manager environment block is persistent across subsequent
> logins (not reboots), even when using different desktop environments.
> This is implemented in /etc/X11/Xsession.d/95dbus_update-activation-env

I don't really understand how it's possible. A new Xsession should be run
every time there's a new cycle. How can the environnement could be preserved?

> 
> As I said, I am not very familiar with all the details around the
> SESSION_MANAGER variable, but it seems like it is only set by GNOMEish
> desktop environments. Even Xfce itself doesn't set the variable. It only
> checks the variable and fails to start if it is set, which is happening
> here.

SESSION_MANAGER is definitely set here:

printenv |grep SESSION_MANAGER
SESSION_MANAGER=local/scapa:@/tmp/.ICE-unix/32176,unix/scapa:/tmp/.ICE-
unix/32176

(32176 is the pid of the currently running xfce4-session process).

> > Just ignoring the fact that a manager might be running doesn't look sound.
> > Can you get in touch with gnome and gdm people about this?
> 
> OK, adding pkg-gnome-maintainers at alioth-lists.debian.net to CC.

Thanks!

Regards,
- -- 
Yves-Alexis
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