Package xorg-x11-server-Xnest

A nested server

http://www.x.org

Xnest is an X server which has been implemented as an ordinary
X application. It runs in a window just like other X applications,
but it is an X server itself in which you can run other software. It
is a very useful tool for developers who wish to test their
applications without running them on their real X server.

General Commands
Command Description
Xnest a nested X server