xserver-xephyr 2:1.7.3.902-1ubuntu6 (i386 binary) in ubuntu lucid

 Xephyr is an X server that can be run inside another X server,
 much like Xnest. It is based on the kdrive X server, and as a
 result it supports newer extensions than Xnest, including render and
 composite.
 .
 More information about X.Org can be found at:
 <URL:http://www.X.org>
 <URL:http://xorg.freedesktop.org>
 <URL:http://lists.freedesktop.org/mailman/listinfo/xorg>
 .
 This package is built from the X.org xserver module.