atlas-iac/docs/CLUSTER_OPERATIONS.md

Running Atlas without an AI assistant

Start here for ordinary operation. The repository describes desired state; Kubernetes and Flux apply it. The implementation record separates completed repairs from open problems. The service inventory covers the whole cluster.

The small map

Concern	Owner and configuration	What it does
Desired Kubernetes configuration	Flux; clusters/atlas/flux-system/	Tracks main, applies service and infrastructure folders
Normal pod replacement and scheduling	Kubernetes; each workload manifest	Restarts failed containers and schedules replacements within placement and resource constraints
Application deployment	services/<name>/, or infrastructure/<name>/ for foundations	Images, resources, probes, storage and networking
Durable application disks	Longhorn; infrastructure/longhorn/	Replication and volume attachment; not an application-consistent database backup by itself
Kubernetes datastore recovery	Native PostgreSQL tools and systemd on titan-db and titan-0b	Hourly protected LAN recovery bundles, independent of Kubernetes
Application backup orchestration	Soteria; services/maintenance/apps/soteria-*	Applies eligible-data policies through the chosen storage backend
Power loss and exceptional node recovery	Ananke; host configuration and scripts/ops/cluster_power_*	Orders shutdown/startup and bounded node recovery; it does not replace storage or database recovery
Node build/configuration	Metis and its sentinels; services/maintenance/	Approved node provisioning and host configuration
CI fault handling	Ariadne; services/maintenance/apps/ariadne-*	Bounded CI diagnosis/recovery; core cluster health must not depend on model calls
Health evidence	Grafana, VictoriaMetrics, Alertmanager; services/monitoring/	Shows application, node and storage evidence; a green controller alone is insufficient

There is no new coordinating framework to learn. Prefer the native owner above. Use a recovery tool only when its documented operation matches the failure.

Five-minute check

Run from the management host with the existing administrator configuration:

kubectl get nodes -o wide
flux get kustomizations -A
flux get helmreleases -A
kubectl get deployments,statefulsets -A
kubectl get pods -A --field-selector=status.phase=Pending
kubectl -n longhorn-system get volumes.longhorn.io

Then check the affected service's health endpoint or UI. Running does not mean ready; Ready does not prove useful application behavior. A detached Longhorn volume may be intentional if its workload is parked. Distinguish that from an attached volume that is faulted or an application waiting for its disk.

Check the control-plane backups separately:

ssh titan-db sudo systemctl status atlas-k3s-backup.timer
ssh titan-0b sudo systemctl status atlas-k3s-replica.timer
ssh titan-db sudo cat /var/backups/atlas-k3s/latest/COMPLETE
ssh titan-0b sudo cat /var/backups/atlas-k3s-replica/latest/COMPLETE

COMPLETE contains timestamps, not database contents. The backup and replica should normally be less than two hours old. Check the last service result too:

ssh titan-db sudo systemctl show atlas-k3s-backup.service -p Result -p ExecMainStatus
ssh titan-0b sudo systemctl show atlas-k3s-replica.service -p Result -p ExecMainStatus

Find the cause before choosing a repair

Symptom	First check	Usual next action
Node NotReady	Power/network, kubelet status, disk space, pressure	Repair/quarantine the node; do not repeatedly restart every application
Pod Pending / FailedScheduling	kubectl describe pod scheduling events	Correct resource requests or eligible capacity; free cluster-wide RAM does not guarantee a compatible destination
ContainerCreating / FailedMount	PVC, Longhorn volume, attachment and engine events	Preserve data; repair the attachment or use a verified healthy node. Do not delete the PVC
CrashLoopBackOff / OOMKilled	Previous container logs and last termination reason	Fix the application or its resource envelope; lifetime restart counts are not a reason for repeated eviction
Ingress 502/503	Service endpoints and backend readiness	Restore the backend or its dependency before changing DNS/TLS
Flux Ready but missing Helm workload	Helm manifest and drift correction	Check that drift detection is enabled and suitable for that release
All cluster API operations fail	titan-db PostgreSQL and control-plane nodes	The datastore is external PostgreSQL; an etcd snapshot procedure will not restore it
CI waiting while applications work	Jenkins queue, agent capacity and node I/O	Let work queue; adding agents to saturated Pi disks makes both CI and services worse

Useful scoped commands:

kubectl -n NAMESPACE describe pod POD
kubectl -n NAMESPACE get events --sort-by=.lastTimestamp
kubectl -n NAMESPACE get endpointslices
kubectl -n NAMESPACE logs POD -c CONTAINER --previous --tail=80

Application logs can contain private data. Inspect them locally and redact before sharing. Never paste Secrets, tokens, source records or inference bodies into a ticket or assistant conversation.

Make a normal change

1. Edit the service's tracked manifest. Placement, requests, limits and probes belong together in that workload's configuration.
2. Render and validate the affected folder; inspect the Flux preview.
3. Commit and push a small change to the tracked branch.
4. Reconcile that service and verify its application behavior and storage.

For example:

kubectl kustomize services/monitoring > /tmp/monitoring-render.yaml
kubectl apply --dry-run=client -k services/monitoring
flux diff kustomization monitoring --path services/monitoring
git diff --check
git diff

After committing and pushing the reviewed files:

flux reconcile kustomization monitoring -n flux-system --with-source
kubectl -n monitoring get deployments,statefulsets,pods

A Flux diff exits nonzero when it finds changes; read the output to distinguish that from a validation failure. Kustomize renders a HelmRelease, not the chart's workloads. For chart values, also inspect the chart's rendered Deployment or StatefulSet. OpenSearch, for example, uses values.nodeAffinity.

Rollback a configuration change by reverting its focused commit and reconciling the same service. Do not blindly revert storage migrations or database changes; those require their recovery procedure. Do not delete data to clear a red status.

Backups and recovery

The external datastore's host backup notes give the actual paths, schedule, credential scope, isolated restore check and rollback. Backups contain sensitive data and remain root-only on approved LAN hosts. They are not encrypted at rest or off-site disaster recovery copies.

Soteria is responsible for eligible application backups, not for making the control plane boot. Live Longhorn snapshots and database-native dumps offer different consistency guarantees. A recent backup indicator is not a restore test. Keep database restore checks and service recovery drills explicit.

The Hermes namespace is excluded from cloud backup policy. Its workspaces can contain material restricted to local infrastructure. Do not remove that exclusion to make a coverage dashboard greener.

A one-day familiarization exercise

• Morning: follow one application from its Flux definition to its workload, storage, service and ingress. Compare those manifests with live objects.
• Before lunch: inspect one scheduling incident and one storage incident using the table above. Identify the responsible component without changing anything.
• Afternoon: run the isolated datastore restore verification, inspect backup timestamps, then make and revert a harmless configuration change through Flux.
• Finish by finding each remaining issue in the implementation record and the corresponding owner/runbook. Confirm access to Git, the management host, the hosts' SSH path and protected recovery material without relying on SSO alone.

This provides a practical route to ownership; it cannot promise that every hardware, storage or database disaster will be solvable in one day.

Physical checks and return to service

For an offline Pi, record the board identity, supply model and its 5 V rating, power/activity LEDs, HDMI boot result, Ethernet link and current router address. Preserve the original SD/USB media. Test with separate known-good spare boot media before concluding that a board has failed; do not clone a live node identity by moving another cluster node's boot card into it.

Pi 5 power must be evaluated at its 5 V output mode, not a charger's headline wattage. A controlled supply-and-cable substitution isolates the power path. Record any inline adapters and USB loads. Do not unplug runtime USB storage on a running node. Titan-11 carries important services; arrange workload movement before disconnecting it. See the official Raspberry Pi power documentation for 5 V / 5 A capability and cable-loss requirements.

A repaired node returns only after stable power, clean storage/kernel logs, reliable networking and representative-load testing. Observe it before restoring normal placement. Titan-14/18 quarantine is explicitly tracked in infrastructure/core/node-maintenance.yaml; prune: disabled protects the Node objects from deletion when that maintenance declaration is eventually removed. Clear spec.unschedulable through Git after validation, then reconcile core.

Container runtime media and Longhorn data disks are separate. A Pi with terabytes of healthy application storage can still stall because containerd, image unpacking and logs live on a small USB flash device. Include the runtime disk in hardware repair and capacity checks.