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CTO (Paperclip Agent) da9777358b feat(os-update): SSH-key drift preflight (DEV-587) 
DEV-586 (2026-09-27) aborted mid-drain because cp-1's pubkey had drifted out
of four nodes' /root/.ssh/authorized_keys — probably Hetzner cloud-init
re-syncing from the HC SSH-keys API on reboot (the operator key is not in
that keyset). Both the apt-phase SSH and the CP peer-probe SSH died once
they tried to reach the drifted targets, and recovery cost real time.

os-update.sh now runs a preflight against the fully-computed plan:
- Reads cp-1's pubkey once (fails loudly if operator can't reach cp-1).
- For every planned worker + CP: proves operator SSH works, then grep-checks
  cp-1's pubkey in /root/.ssh/authorized_keys. Missing pubkeys are appended
  via the operator's own SSH (auto-heal). Verify via grep after the write.
- Nodes still unreachable at the end block the whole cycle with the exact
  fix command in the log — nothing gets drained until this passes.
- Preflight report: /tmp/os-update-<UTC-ts>/ssh-preflight.txt (ok/repaired/
  problem lists) as audit trail.
- Escape hatch: --skip-ssh-preflight for bootstrap scenarios.

Also factors the node->ssh-endpoint case into a shared node_ssh_endpoint()
helper so the preflight, finalize/apt-history loop, and any future call site
can't drift apart.

Verified end-to-end against the live cluster: all planned nodes reachable
and cp-1's pubkey currently present on cp-2/cp-3, worker-1..6.

Co-Authored-By: Paperclip <noreply@paperclip.ing>
2026-10-11 02:57:31 +00:00
..
cluster-health.sh Add weekly rolling OS-update procedure for k3s nodes (DEV-462) 2026-08-09 15:55:39 +00:00
ensure-node-docker.sh feat(os-update): reconcile Docker + label after node updates (DEV-499) 2026-08-16 20:22:43 +00:00
os-update.sh feat(os-update): SSH-key drift preflight (DEV-587) 2026-10-11 02:57:31 +00:00
README.md feat(os-update): SSH-key drift preflight (DEV-587) 2026-10-11 02:57:31 +00:00
update-cp-1.sh os-update: generalize CP procedure to HA cp-1/cp-2/cp-3 (DEV-515) 2026-08-23 01:53:14 +00:00
update-cp-node.sh fix(os-update): accept 401/403 as /livez alive in CP reboot poll (DEV-566) 2026-09-06 01:47:47 +00:00
update-node.sh fix(os-update): add k3s-worker-6 to SSH target maps (DEV-566) 2026-09-06 01:04:35 +00:00

README.md

OS Update Automation

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

Authoritative doc: ../../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 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.
  • SSH-drift preflight (DEV-587): before draining anything, verify the operator can SSH to every planned node and that cp-1's pubkey is present in each target's /root/.ssh/authorized_keys. Missing pubkeys are auto-appended via the operator's own SSH; nodes that reject the operator entirely fail the whole cycle with the exact repair command. Preflight report is written to /tmp/os-update-<UTC-ts>/ssh-preflight.txt. Escape hatch: --skip-ssh-preflight for bootstrap.
  • 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

# 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.