I've transferred the core of a computer into a 3D-printed case, reducing the volume it took up on my shelf. It's been part of my Proxmox experimentation, getting a feel for the software by playing with different capabilities. One notable experiment was putting two machines together into a cluster, and seeing how easy and seamless it was to migrate virtual machines between them. It was really neat!

Thankfully, the Realtek network problems which forced my hand with VM migration has been resolved, and my Dell 7577 has run reliably for several months. Since it draws less power than a Mini-ITX desktop, I decided to migrated all my virtual machines back to the 7577. This will free my Mini-ITX system to be powered down for now and available for other experiments in the future. I found instructions for removing a Proxmox cluster node, but the command failed with the error message: "cluster not ready - no quorum? (500)"

Major cluster operations requires quorum, defined as a majority of nodes ((number of nodes/2)+1) to be online and actively participating in cluster operations. Adding and removing cluster nodes qualify but apparently there are built-in exceptions for adding the first few nodes because by definition we have to start with a single node and build our way up. But there is no built-in exception for removal and thus I'm prevented from dropping node count back down to one.

Searching Proxmox forums, I found a workaround in thread Another "cluster not ready - no quorum? (500)" case. We can suppress quorum requirements with the command "pvecm expected 1", then proceed with the operation that typically require quorum like removing a cluster node. Since quorum requirement exists to make sure we don't fatally damage a Proxmox cluster, this is a very powerful hammer that needs to be wielded carefully. We have to know what we are doing, which may include requirements outside of the actual act of removing a node.

In my case, I am responsible for making sure that the removed node never gets on the network again in its current state. I unplugged the network cable from the back of the motherboard and used a Windows 10 installation USB drive to overwrite Proxmox with Windows 10. That should do it.