stoolpigeon's Journal: GDM/KDM Weirdness

Something has been bugging me for a bit. I have 2 Fedora 16 machines - 1 is a 64 bit desktop and the other a 32 bit laptop. I have done too much different between the 2 but I like the login box on the one better than the other. I wasn't sure how they came to be different - but they are. So I tried to get them to match. This led to the realization that the changes I made in the System Setting -> Login Screen menu had no effect. I googled around but couldn't find anything that helped. A lot of what I found was outdated.
 
It seemed to me that the most obvious reason that the changes didn't show up was that I was using GDM and the interface in System Settings is to change KDM. So I set out to get that switched. ( That it would be using GDM is no surprise as I just do a regular Fedora install, include KDE and switch to that as the default. ) That took a while because the KDE documentation doesn't work. I installed the program system-switch-displaymanager-gnome and I ran it. I chose KDM. Doing so created a file /etc/sysconfig/desktop that contained one line - DISPLAYMANAGER=KDE. This did not change the behavior. I just kept on digging - finally I ran across a fedorforum.org thread that mentioned changing the fallback order in /etc/X11/prefdm I took a look at that file on my system. To me it looked like what was in /etc/sysconfig/desktop should do what I wanted, but just for fun I switched the fallback order to have KDM first. When I did - my system started using KDM and now the changes in System Settings take effect.
 
I'm guessing if I installed from the KDE spin of Fedora, this might not be a problem. But I'm still at a loss as to why my desktop file had no effect. The first part of prefdm looks like this:

# Run preferred X display manager
preferred=
splash_quit_command=""
if [ -f /etc/sysconfig/desktop ]; then
                . /etc/sysconfig/desktop
                if [ "$DISPLAYMANAGER" = GNOME ]; then
                                preferred=/usr/sbin/gdm
                elif [ "$DISPLAYMANAGER" = KDE ]; then
                                preferred=/usr/bin/kdm
                elif [ "$DISPLAYMANAGER" = WDM ]; then
                                preferred=/usr/bin/wdm
                                splash_quit_command="plymouth quit"
                elif [ "$DISPLAYMANAGER" = XDM ]; then
                                preferred=/usr/bin/xdm
                                splash_quit_command="plymouth quit"
                elif [ -n "$DISPLAYMANAGER" ]; then
                                preferred=$DISPLAYMANAGER
                                splash_quit_command="plymouth quit"
                fi
fi

It seems to me that ought to work - but for whatever reason it does not. Now I have it working the way I'd like by setting KDM as the first fallback and that makes me happy. I think I'll file a bug report - though I hope it is a bug and not something I am missing.

Moo

[Chacham]

Make sure you look at both system and user settings. Sometimes the other one is being used.

Re:

[stoolpigeon]

Good point - and I did consider it - though I just don't know enough about how it all works to follow that path. Basically I would just search on stuff like "KDM changes not saving" or "switching from gdm to kdm" and so on, with various extra info. thrown in.

So I was looking all over the place for anything that would put me on the right track. My one guess in this regard though - was that in a way this seems like it would have to be a system wide choice as it comes into effect before any user is logged in -