(This is a minimal instruction for me to remember how to start it. I'll expand it at some point, including how to set up the config file. - Dawn)
If you have your Vrui.cfg file set up to use a space ball or related input device on your PC, you need to start the device driver. To do so, from a terminal window, type:
cd ~/Vrui-1.0/bin # (or the location of your Vrui.cfg file) ./VRDeviceDaemon
The VRDeviceDaemon has it's own configuration file. For something like the minicaves (e.g. 3d TVs with optical tracker). If the VRDeviceDaemon doesn't find deviceNames or some other section required for your particular environment, you can start the VRDevice Daemon with a path to the configuration file you want to use.
<vrui path>/bin/VRDeviceDaemon <path>/VRDevices.cfg