"For gdm, edit /etc/gdm/gdm.conf (on some systems this may be
located at /etc/X11/gdm/gdm.conf). For kdm, edit
/etc/kde3/kdm/kdmrc. In both cases, you must change the line in the
[Xdmcp] section so it reads
"Enable=true
"If there's no Enable line, add it. Save the file, and restart
the display manager so the change will take effect. You can also
use the gdmsetup utility to configure gdm graphically, if you
prefer."
