If you are creating KDM themes (either for KDE3 or KDE4) you may find it very tiring of restarting the Xserver everytime that you change something in the xml file and want to see how it looks.
I recently came across a very nice way of checking your KDM theme from within the current session without having to restart the Xserver. It also allows you to easily take screenshots of your theme using the ksnapshot.
The following instructions originate from the user moonrise (see link below). I upload them here as well.
Here is what you have to do:
1. Install Xephyr... Either through Adept Manager or through konsole:
"sudo apt-get install xserver-xephyr"
2. Edit "/etc/kde4/kdm/kdmrc" with kate as root.
konsole: "kdesudo kate /etc/kde4/kdm/kdmrc"
3. Edit "/etc/kde4/kdm/Xaccess" with kate as root.
konsole: "kdesudo kate /etc/kde4/kdm/Xaccess"
Change: #* #any host can get a login window
to: * #any host can get a login window
4. Reboot your system.
5. After rebooting. Log in. Start Konsole.
In konsole: "Xephyr -query localhost -screen 800x600 :1"
if the last command gives you a black sceen, try:
"Xephyr :1 -query 127.0.0.1 -screen 800x600"
6. This should bring up a screen @ the designated resolution of 800x600. You can play with the resolution to check if your theme looks fine under different resolutions.
7. You can also use "Ksnapshot" to make a screen shot of the resulting screen that appears.
8. If you are using KDE3 change the word "kde4" to "kde3".
Note that you do not have to install-uninstall your theme everytime you make a change in the xml file. Instead, edit directly your installed xml file (for example, the one in "/usr/share/apps/kdm/themes/your_theme") and then call Xephyr. You will see that the changes have taken place.