Partitioning scheme for workload VMs (CAPN)

Convention for the VMs (virtual machines) that CAPN (Cluster API Provider for Incus) provisions as workload clusters (for example demo, see Workload Clusters). It is a template for the base image of those VMs, not a measured state.

It comes from the partition review of the 3 bare-metal nodes (the playbook-discovery.yml report, section "Recomendaciones — esquema de partición del SO"): no node has /var separate from /, and the swap of each one was sized with a different criterion (between 13 % and 94 % off from min(RAM/2, 8GB)). On an already installed node this cannot be fixed without repartitioning the mounted root; on a new VM it is defined from the first boot.

Scheme

Partition	Size	Filesystem	Notes
/boot (or /boot/efi with UEFI)	1 GB	vfat/ext4	Same as the 3 bare-metal nodes
swap	min(RAM/2, 8GB)	swap	Fixed formula, the same on every VM
/var	≥20 % of the disk, or 20 GB minimum	ext4	Separate from /: runaway growth of logs, containerd images or local volumes does not fill the root
/	Rest of the disk	ext4	Base system

Why separate /var

K3s workloads (containerd, logs, image cache, local-path-provisioner/OpenEBS if used inside the VM) all write under /var. Without a separate partition, if that grows out of control it can fill / and bring down the whole node, not just the workload. On already installed bare metal, separating /var requires reinstalling; on a new CAPN VM it costs nothing to define it in the template from day one.

Applying it

The scheme belongs in the base image or template that CAPN uses to provision the VMs, not in Ansible after installation. This repo does not have that template yet.