JeoS is shorthand for “just enough operating system.” It’s a simple short install process that’s hidden in the server installation ISO. On the startup you just have to press F4 and select “Minimal virtual machine”. Rather than installing the entire Ubuntu server package you get an extremely pruned-down version that only includes the absolute bare essentials to get a server running. If your like me and believe that VMs should be created for a singular purpose only, then it will make your life even easier to create a bunch of small VMs. According to their specs you should expect something like 380MB disk images running in about 128MB of RAM.