Useful commands for X11
Welcome to this short summary of useful commands for X11.
I have written it to avoid having to resort to googling next time I forget Xephyr.
Also it might be interesting for others as well…
Servers inside your X11 server
xoo with a ipaq3800 skin
Why would you want to run a X11 server on your X11 display
Well for starters you might want to try out your UI on a device with a lower screen resolution than your development machine.
You might also want to code an application running at a different colour depth than you desktop, maybe a rotozoomer in 16bit 
You may also simply want to try out a couple of applications on a low res. screen prior to buying a table with a low res. screen…
Xoo
A wrapper for xnest and Xephyr that allows one to create a skinned X11 display.
You can even have working buttons that you can click.
sudo apt-get install xoo
Xnest
Haven’t used it myself.
As far as I know Xephyr has some advantages in the supported extensions over xnest
sudo apt-get install xnest
Xephyr
Based on the kdrive xserver supporting extensions such as render and composite.
xnest package actually recommends this package over it self…
sudo apt-get install xserver-xephyr
Utilities and tools
Xpra aka. “screen” and turbo for X11 applications
Screen is a wonderful tool for command line tools.
Xpra gives you the same capacity to leave the program running on the remove even if you close/losses the connection.
Also xpra “compresses” the stream of X11 commands by using a different protocol than X11, reducing the problems caused by low latency connections.
sudo apt-get install xpra
