Thanks for that, this is progress of some kind. I do not have any /usr/local/bin/start_xephyr.sh script. But using your Xephyr command line I get a big black box. Groovy. Running the little sample program base.c makes most of the screen go grey. Killing the program makes it black again. I therefore conclude that GUI programs may well be able to use this thing from inside scratchbox. I'll need to go through the rest of that document to figure out how to make it do something more useful.

It would be nice to see the actual hildon desktop inside that black box. Any tips on making that work?

BTW, my goal is to tweak modest a bit. I got as far as trying to build it, but it has an unmet dependency on calendar-ui-widgets-0-dev that won't install. I'm guessing I'll be able to find that in one of the other repositories, but I will probably want to run the Maemo 5 package manager to do that, which means getting the package manager to work in Xephyr first...