Proxmox is a pretty nice virtualisation solution for the medium enterprise. It’s bigger than Virtualbox, smaller than Openstack, and easy to implement on both as single machine or a whole cluster. Unfortunately, the developers are struggling to pay the bills. So with the 3.1 release they have followed the path of “Subscription versus Community.” Users without a subscription are now treated to this dialog every time they login:
You do not have a valid subscription for this server. Please visit www.proxmox.com to get a list of available options.