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jakman85andClaude Opus 4.8 e8c555cfeb Initial baseline: home platform (k3s + Longhorn) specification repository

Greenfield spec set for a GitOps-driven PaaS+IaaS home platform: vision &
requirements (R-* IDs), architecture, 14 domain specs, 11 ADRs, roadmap
(phases + workstreams), and AI-agent coordination (roles, protocol,
definition-of-done, task board).

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

2026-08-15 22:37:56 -05:00

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ADR-0005 — VM workloads: KubeVirt + CDI

Status: Accepted
Date: 2026-08-15
Serves: R-PLAT-03, R-PLAT-04, R-STATE-01
Supersedes: —

Context

Not everything fits in a container. The platform must run VMs, but the operator must manage them through the same Kubernetes API/CLI/YAML/GitOps as containers, with the same network isolation, egress classes, storage durability, and observability — no separate hypervisor management plane for application workloads.

Decision

Use KubeVirt to run application VMs as Kubernetes custom resources (VirtualMachine / VirtualMachineInstance), with CDI (Containerized Data Importer) to provision VM disks onto Longhorn PVCs. VMs run on the same Cilium network (inheriting default-deny + egress classes) and are managed by Flux like any other workload. virtctl provides console/lifecycle helpers alongside kubectl.

Alternatives considered

Proxmox / standalone hypervisor + separate IaC — a second management plane and tooling; breaks the "same Kubernetes surface" requirement (R-PLAT-03). (The operator's prior environment used Proxmox; this platform deliberately unifies on Kubernetes instead.)
Harvester (SUSE) — HCI built on KubeVirt; heavier and opinionated about the whole node OS; k3s
- KubeVirt keeps one lightweight cluster for both containers and VMs.
Containers only — rejected: the requirement explicitly needs a VM escape hatch.

Consequences

One control plane, one GitOps flow, one network/storage/observability model for containers and VMs.
Nodes must expose virtualization extensions (nested virt in dev KVMs; native on prod) — a node baseline prerequisite (02).
VMs are heavier than pods; capacity planning on the 3-node cluster must account for them.
At least one representative VM workload must be proven in dev/test so the IaaS path is real (06).
VM guest updates use in-guest automation (R-UPD-*), distinct from container image tag bumps.

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