Graças a estas perguntas " Por que meu GDM está em um TTY diferente do meu ambiente de área de trabalho? "Descobri o motivo das duas sessões do xorg. O gerenciador da área de trabalho do Gnome usa duas sessões xorg que agem como um saudador (login) e as outras como uma sessão do usuário. No passado, uma sessão do xorg foi criada com o root e depois transformada em uma sessão do usuário. No entanto, para futuros planos de desenvolvimento, a decisão de separar essas sessões foi decidida.
Leia mais sobre isso aqui:
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Let me explain a bit more about why we did this.
Previously, we launched one X server as root, and then when you logged in, we "morphed" it into the session X server. If you went to fast user switching, we then launched a second X server on-demand.
For security reasons, and Wayland porting reasons, we now launch the X server and Wayland server within the user's session, instead of starting one as root.
The way that we do this is that we launch two X servers, one for the gdm greeter session, and for the session user.
It would be entirely possible to tear-down the greeter after we've switched to the user session, it just requires a bit more code, but unfortunately it wouldn't be possible to put both the greeter session and the user session on VT1, since we'd have to launch the user session first, and then tear down the greeter session, and we can't be in that intermediate state while there are two X servers on the same VT at the same time.
I just forgot about the resource issues around keeping around two gnome-shell instances. I'll have a chat with Ray to see if we want to tear down the greeter session and then launch it on demand for user switching / logout to save on resources.