> free of 16, ~198 GiB disk free; libvirt/QEMU/Vagrant **not yet installed** ·
> 2026-06-18.
## Decision
### 1. Virtualisation approach: libvirt/KVM directly (Approach A)
A golden Debian-13 genericcloud qcow2 is cached locally on ubongo. Each run boots an
ephemeral qcow2 **overlay** backed by it (the golden image is never mutated), seeded
via cloud-init NoCloud, driven by a **stdlib-only** Python driver (`scripts/
integration-vm.py`) over `virsh` / `virt-install` / `cloud-localds`. No `libvirt-
python` dependency — the driver stays portable and the role stays lean.
### 2. Fidelity envelope
The bugs are **post-boot**, not in the provisioning path. A lightweight local hypervisor
is sufficient: real OS, real kernel netfilter, real Docker daemon, real published-port
DNAT, a **real reboot**, and the coordinator running inside the VM (so the VM forms its
own one-node mesh, reproducing the circular bootstrap). The Proxmox provisioning chrome
is not mirrored.
### 3. Scope: one throwaway VM at a time, instantiated from real inventory
The first profile is **"be askari"** — a single box running Docker host + NetBird
coordinator + mesh peer, mirroring the host whose incident motivates this work. The
mechanism is generic: swap the profile to "be" any inventory host. Multi-VM topologies
are a deferred extension.
### 4. Acceptance: self-validating against the real failure
The harness is accepted when it can, on a local VM:
1. Apply `base` (firewall on, no `docker_host` container-forward drop-in) to a Docker
host, reboot, and observe the **2026-06-17 breakage** (Docker forwarding dead,
services down). If step 1 passes, the harness is not faithful.
2. Apply the `docker_host` container-forward fix, re-run, and **survive the reboot**.
### 5. Tiered cert fidelity via a `--certs` knob
DNS-01 is what makes real certs possible without public inbound (validation is
out-of-band via a Gandi TXT record; the VM needs only outbound to ACME + Gandi, which
the isolated NAT network provides):
| Tier | Description | Default? |
|---|---|---|
| `internal` | Caddy `tls internal` — zero deps, instant. For incident repro and runs where certs are not under test. | Yes |
| `le-staging` | Real DNS-01 ACME against Let's Encrypt **staging** — real caddy-gandi path, real cert files/renewal, untrusted root, effectively no rate limits. | Built in v1; use when testing the ACME/cert path. |
| `le-prod-wildcard` | A real trusted `*.test.wingu.me` wildcard, **issued once, persisted on ubongo, reused** across runs. | On-demand only. Accepted risk recorded as R6 in `docs/security/accepted-risks.md`. |
A deliberate "no-egress" failure scenario (reproducing FRICTION 2026-06-17 #4 —
`netbird-server` FATAL-loops on GeoLite2 download when egress is lost) forces
`internal`, since ACME requires egress.
### 6. The toolchain is Ansible-managed
A new non-service role (`integration_test`, `control` group) installs and enables
libvirt + QEMU + virtinst reproducibly. The driver manages the golden image lazily on
first run (keeping the role lean; no fiddly download/refresh logic in Ansible). The
repo owns ubongo's state.
### 7. Stubs live in an overlay file, never in the real inventory
Transient inventory entries for the test VM are generated at runtime as a single-host
file. Stubs (cert tier, in-VM coordinator endpoint, VM connection details) live in
`tests/integration/overrides/<host>.yml` — an explicit, reviewable overlay. The real
inventory is never touched, so `make tf-inventory` and "don't edit inventory directly"
stay intact.
## Consequences
- **Reconciles ADR-015:** ubongo runs ephemeral KVM test VMs as part of its
local-test-runner role — it is still not a production hypervisor. A default VM
(~2 vCPU / 3 GiB / 20 GiB thin overlay) against ~13 GiB free is comfortable; the
driver enforces **one integration VM at a time** (resource guard, name-prefix
`boma-it-*`) and refuses to start below a free-RAM threshold.
- **Operationalises the standing rule:** "firewall/sshd/boot changes must be tested on
a real VM with a real reboot before they touch a live host" (FRICTION 2026-06-17 #6)
becomes a concrete, runnable step documented in `docs/runbooks/integration-testing.md`.
- **Accepted risk R6:** `le-prod-wildcard` runs pass the production Gandi PAT
(`vault.gandi.pat`) to an ephemeral local VM and write transient `_acme-challenge`
TXT records into the real `wingu.me` zone. Scope: on-demand only; `le-staging` is the
default. Compensating controls: ephemeral VM, isolated NAT network, TXT records
auto-removed by Caddy after validation.
- **Three safety invariants** make the test tool itself safe:
1. The transient inventory contains only the test VM — no real host is ever in scope.
2. "Be askari" points NetBird at the in-VM coordinator — the VM forms its own one-node
mesh; it never enrols in the real mesh.
3. Test VMs sit on an isolated libvirt NAT network — outbound NAT for ACME/image pulls
only, not reachable to the LAN (`10.20.x`) or the real mesh.
- **Diagnostics on failure** (catching a bug is the point): failure keeps the VM and
dumps `nft list ruleset`, `docker ps`, `ss -tlnp`, `journalctl -b`,
`systemd-analyze critical-chain`. `make test-integration-clean` reaps all `boma-it-*`
orphans. Diagnostics land in gitignored `~/integration-runs/<ts>-<host>/`.
- **Future pinch:** concurrency with the Level-4 Chromium/Playwright stack (ADR-017)
competes for ubongo RAM. The resource guard is the v1 answer — one integration VM at a
time; don't run alongside a heavy Level-4 session. Revisit at `/capacity-review`.
**Out of scope (v1):** multi-VM mini-cluster (inter-host mesh dataplane); CI gate
(this is an interactive, agent-driven pre-deploy check; CI stays lint + Molecule per
ADR-008/010); the Proxmox provisioning path (the bugs live in the boot/kernel/Docker
layer, not provisioning).
## What was ruled out
| Option | Reason |
|---|---|
| **Proxmox VE nested on ubongo** | Highest fidelity including the provisioning step, but heavy (nested virt, RAM), in tension with ADR-015, and the incident bugs do not live in provisioning. |
| **Vagrant + vagrant-libvirt** | Mature lifecycle/snapshots, but adds the Ruby/Vagrant ecosystem + a fragile plugin; boxes drift from the real Debian cloud image; the reboot→assert sequence still needs custom logic. |
| **terraform-provider-libvirt** | Declarative and reuses TF, but poor at the imperative apply→reboot→re-apply test sequence; adds throwaway state; blurs ADR-006's "TF owns *production* VM existence on Proxmox" boundary. |
