Replacing xnest with Xephyr. Xephyr is a kdrive based X Server which targets a window on a host X Server as its framebuffer. Unlike Xnest it supports modern X extensions ( even if host server doesn't ) such as Composite, Damage, randr etc (no GLX support now). It uses SHM Images and shadow framebuffer updates to provide good performance. It also has a visual debugging mode for observing screen updates.

http://www.freedesktop.org/wiki/Software/Xephyr


Xephyr works full screen too.

Xephyr -fullscreen -ac :1

Using this feature, it is possible to insert this command in every LTSP session, so that when user logs in and choose the machine, automatically he or she gets it on the screen, without caring of launching it manually. User does not need to activate VDD manually from the server, but gets it full screen just by clicking an icon (for example). We could even think of putting a simple script in

~.kde/Autostart/