alt Hacker NewsOut of all mainframe OSes, VM is the most approachable imo, as long as you grasp minidisks and how s390 device addressing works, it becomes just a somewhat clunky DOS. I would also suggest checking out the 2.4 VM ADCD, it is a package with basically all the interesting software, and it is out there if you look for it.
> a somewhat clunky DOS
And the Community Edition even has a handy DIR command for you.
This document has a lot of things left to add - the machines can really be a lot more interesting. So far, I haven't figured out how to connect my real printer over the network, the other machine with shared disks but no OS, and even creating a new VM for our user. I also know there are a lot of other interesting things on the base CE image that can be super cool to show a newcomer.