# OS Update Automation

Scripts that implement the weekly rolling Ubuntu OS-update procedure.

**Authoritative doc:** [`../../OS_UPDATE_PROCEDURE.md`](../../OS_UPDATE_PROCEDURE.md) — read it first. The scripts here mirror that procedure step-for-step.

## Files

| Script | Purpose |
|--------|---------|
| `cluster-health.sh` | Non-zero if any node is not Ready, any pod is not Running/Ready, or any Deployment/StatefulSet is below its desired replica count. Used at preflight and after each node. |
| `update-node.sh <node>` | Drain, apt-update, reboot-if-required, wait for Ready, ensure Docker on labeled nodes, uncordon, post-node health check. Retriable per-node. |
| `ensure-node-docker.sh <node>` | Idempotent: on nodes labeled `basicstack.de/docker=true`, install docker.io if missing, `apt-mark manual`, enable+start the docker service, wait for `/var/run/docker.sock`, re-apply the label. No-op on nodes without the label. Called from `update-node.sh` between "kubelet Ready" and "uncordon"; also runnable ad-hoc for recovery. |
| `os-update.sh` | Full cycle runner: preflight → etcd snapshot → ordered per-node loop → finalization + apt history digest. |

## Order of operations (encoded in `os-update.sh`)

1. Workers with no stateful affinity concerns first.
2. `fsn1` workers (potential Stalwart hosts) last among workers — see [`stalwart-datacenter-affinity`](../../K3S_OPERATIONS.md) note.
3. `k3s-cp-1` last (single control plane).
4. One node at a time. Never in parallel.

## Guardrails the scripts enforce

- Preflight cluster health failure → refuse to start.
- Drain with a PDB conflict → uncordon and mark the node `SKIPPED_DRAIN_FAILED`, never `--force`.
- Node reboot fails to come back within timeout → hard stop, escalate. Do NOT rebuild the node or touch k3s config.
- kubelet doesn't return `Ready` → hard stop, escalate. Do NOT touch k3s config.
- Post-node cluster health check red → hard stop, do not proceed to the next node.
- Absolute rule: **no k3s config, no manifests, no PVs, no service files touched** — apt/dpkg only.

## Typical invocations

```bash
# Dry-run: print the ordered plan, touch nothing.
./os-update.sh --dry-run

# Full cycle (weekly, triggered by the Paperclip routine).
./os-update.sh

# Retry a single node (after fixing a manual issue).
./update-node.sh k3s-worker-3

# Restart a partial cycle from a specific node onward.
./os-update.sh --start-from k3s-worker-4

# Ad-hoc: reconcile Docker on a single node (e.g. after emergency ops).
./ensure-node-docker.sh k3s-worker-3
```

Logs land in `/tmp/os-update-<UTC-timestamp>/` on the machine that ran the cycle.