You are probably better of creating your own VM and booting the ISO of it and configuring as needed. If your linux knowledge is as poor as mines then I would say stick with the prebuilt appliance. (I am striving to setup a linux Nagios box all by myself - interesting!!)
However, I have now searched the website (cool application!) and it looks easy enough to install. Seems to be as easy to install as ESX using the GUI method? Have you tried building it from scratch? The link for the ISO file: http://www.rpath.org/rbuilder/downloadImage?fileId=26707
Check these links out: they will help. The UUID normally changes and it means your eth0 interface disappears since the MAC address of the NIC on your VM doesn't match the one that was used when the original VM was created. I had this problem with my pre-built nagios linux appliance too.
https://forums.openfiler.com/viewtopic.php?id=2025
https://forums.openfiler.com/viewtopic.php?id=2043
https://forums.openfiler.com/viewtopic.php?id=1997