Re: [gdm-list] gnome-screensaver authenticates users through GDM

[Jeff Cai <Jeff Cai Sun COM>]

On Sun, 2010-01-17 at 23:16 -0800, Alan Coopersmith wrote:
> Jeff Cai wrote:
> > On Fri, 2010-01-15 at 10:02 -0800, Alan Coopersmith wrote:
> >> Brian Cameron wrote:
> >>>    Another advantage is that on the console, this could be written so
> >>>    the authentication dialog screen is presented on a separate VT and
> >>>    runs as the "gdm" user, providing better TrustedPath security.  This,
> >>>    for example, ensures that the authentication dialog is not using
> >>>    the same Xauth cookie as the user's session, avoiding any possible
> >>>    interference or snooping from a userland program.
> >> Running unlock on another X server actually provides even more benefits:
> > 
> > Currently, before a user logs in GNOME, I find root user's Xorg keeps
> > running. Why it is not a normal user's X server like 'gdm'?
> 
> Xorg starts as root to have the permissions needed open & initialize devices.
> On Solaris & OpenSolaris, there's a backchannel between gdm & Xorg to provide
> a username to switch to when it should run as someone else - this happens at
> login, but presumably not for the mini-session gdm now runs before login.
> (I suppose it could do so, would just need to update the gdm patch that does
>  so - but I haven't verified that Xorg can switch uids between non-root users
>  without restarting - that would need to be tested.)
> 

Thanks, Alan

I have a doubt: Can two X servers be running for the same set of DISPLAY
at the same time? If yes, how can I know which server what I input goes
to?

Jeff