How do I use `Xephyr` and `Xnest`, the nested X servers?
All of the following applies to both Xephyr and Xnest. Xephyr is recommended, as it is currently maintained at X.org while Xnest has fallen in to disrepair. Furthermore, Xephyr supports newer X extensions that Xnest does not support. However, for those who choose to use Xnest, in all of the following Xnest may be substitutded for Xephyr.