Graphical Display Managers

D. Michael McIntyre michael.mcintyre at
Sun Apr 27 13:45:48 UTC 2008

On Sunday 27 April 2008, Michael wrote:
> What is the difference between GDM/KDM/XDM?

XDM is the generic X11 graphical login manager.  You get a username and a 
password box, and little else.  GDM and KDM are from GNOME and KDE 
respectively, and they tend to feel more like GNOME or KDE respectively.  Any 
of the three will get the basic job done.  The differences lie in things like 
being able to log in a user automatically, displaying icons for users, sound 
effects, background wallpapers, etc.  KDM and GDM are substantially similar 
to each other, but subtly different.

> What is the difference 
> between typing KDM/GDM/XDM at the command prompt and typing startx at
> the command prompt?

If you type kdm or gdm or xdm at the command prompt, I don't think any of them 
will work.  You should use /etc/init.d/kdm | xdm | gdm to start these.

The main practical difference between using one of these and just running 
startx is what kind of background you get behind your splash screen.  On a 
typical KDM-based setup logging into a KDE session, you get a nice wallpaper 
behind the "KDE is starting up" display.  If you use startx, you get a plain 
gray background instead. That's the biggest difference, really.  There might 
be some other, more subtle differences with respect to environment variables 
and so on.

> I am asking because I downloaded Ubuntu and then download all of the KDE
> stuff.  However, it seems GDM is still the current graphical manager.
> I just assumed (yes, I know) that by downloading and running KDE stuff,
> that KDM would then become the default graphical manager.

If you sudo dpkg-reconfigure kdm (or gdm or xdm) you should get the option to 
pick which one you want to run.

In the end, it barely matters though, so don't pull your hair out.

D. Michael McIntyre 

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