xserver-xephyr 2:1.3.0.0.dfsg-12ubuntu8.3 (hppa binary) in ubuntu gutsy

 xserver-xephyr is an X server that can be run inside another X server,
 much like xnest. xephyr though, is based on the kdrive X server, and as a
 result it supports newer extensions than xnest, including render and
 composite.