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Kind Node IP Mismatch After Crash Runbook

Symptoms

  • One or more nodes stuck in NotReady after Docker / Rancher Desktop crash and restart
  • Pods stuck in Terminating or Pending state
  • ingress-nginx controller unable to schedule a replacement pod — all *.idp.local URLs return 502 / unreachable
  • kubectl get nodes shows a node as NotReady even though its Docker container is running
  • Kubelet logs inside the node container show repeated connection errors to the old IP:
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dial tcp 172.18.0.X:6443: connect: connection refused

Root Cause

Kind runs each cluster node as a Docker container. When Docker or Rancher Desktop crashes and restarts, it may reassign container IPs — the control-plane node gets a different IP than what is baked into /etc/kubernetes/kubelet.conf. The kubelet then cannot reach the API server, so the node reports NodeStatusUnknown and stays NotReady.

This cascades to: - Pods that were running on the affected node get evicted and enter Terminating - Replacement pods that require a NotReady node (e.g. DaemonSets, ingress with node affinity) stay Pending - inotify resource limits may also be exhausted after the restart, causing kube-proxy to crash

Diagnosis

1. Confirm the IP mismatch

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# Current Docker container IPs
for c in $(docker ps --filter "name=idp-mvp" --format "{{.Names}}"); do
  echo "$c: $(docker inspect $c --format '{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}')"
done

# IPs registered in Kubernetes
kubectl get nodes -o wide

If the control-plane's Docker IP differs from its INTERNAL-IP in kubectl, you have an IP mismatch.

2. Confirm the API server cert covers the new IP

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docker exec idp-mvp-control-plane openssl x509 \
  -in /etc/kubernetes/pki/apiserver.crt -noout -ext subjectAltName

The new IP must appear in the IP Address: list. If it does not, a cluster recreate is required (see Prevention below).

3. Check kubelet.conf target

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docker exec idp-mvp-control-plane grep server: /etc/kubernetes/kubelet.conf

It should match the current Docker IP of the control-plane.

Fix

Replace 172.18.0.NEW with the current Docker IP of the control-plane container (from step 1 above).

Step 1 — Update kubelet.conf with the new IP

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NEW_IP=$(docker inspect idp-mvp-control-plane \
  --format '{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}')

docker exec idp-mvp-control-plane \
  sed -i "s|https://[0-9.]*:6443|https://${NEW_IP}:6443|g" \
  /etc/kubernetes/kubelet.conf

Step 2 — Restart the kubelet

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docker exec idp-mvp-control-plane systemctl restart kubelet

Step 3 — Wait for the node to recover

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kubectl get nodes -w
# Expect: idp-mvp-control-plane   Ready   control-plane   ...

Step 4 — Fix inotify limits if kube-proxy is crash-looping

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# Check
kubectl get pods -n kube-system -l k8s-app=kube-proxy

# If any pod shows Error / CrashLoopBackOff with "too many open files":
docker exec idp-mvp-control-plane sysctl -w fs.inotify.max_user_instances=1024
docker exec idp-mvp-control-plane sysctl -w fs.inotify.max_user_watches=655360

# Delete the crashing pod so the DaemonSet recreates it
kubectl delete pod -n kube-system <kube-proxy-pod-name>

Step 5 — Verify full cluster health

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# All nodes Ready
kubectl get nodes

# No non-Running pods (excluding expected failures like catalog-exporter)
kubectl get pods -A --no-headers | grep -v Running | grep -v Completed

ingress-nginx should reschedule and reach Running within ~60 seconds, restoring all *.idp.local URLs.

Step 6 — Fix kagent-controller if still CrashLoopBackOff

After DNS recovers the kagent-controller may still crash because the startup probe kills it before the pgvector DB migrations complete (default window is only ~60 s).

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# Check
kubectl get pods -n kagent | grep kagent-controller

# If CrashLoopBackOff, widen the startup probe window and restart
kubectl patch deployment kagent-controller -n kagent --type='json' \
  -p='[{"op": "replace", "path": "/spec/template/spec/containers/0/startupProbe/failureThreshold", "value": 12}]'

kubectl rollout restart deployment/kagent-controller -n kagent

# Wait for 1/1 Running
kubectl get pods -n kagent -w | grep kagent-controller

Known Harmless Failure

catalog-exporter in the monitoring namespace will stay in CrashLoopBackOff whenever Backstage is not running via Docker Compose. It tries to reach backstage.default.svc.cluster.local:3000 (in-cluster DNS), which does not exist when Backstage is down. Start Backstage to resolve it:

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./scripts/bootstrap-local.sh --start-backstage

Prevention

  • Add a fixed IP subnet to Docker: configure Docker Desktop / Rancher Desktop to use a stable subnet so container IPs do not change across restarts. Set this in Docker Desktop → Settings → Docker Engine:

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    {
  "default-address-pools": [
    { "base": "172.18.0.0/16", "size": 24 }
  ]
}

    Kind still assigns IPs dynamically within that pool, but stability is improved on clean restarts.

  • Graceful shutdown: use ./scripts/bootstrap-local.sh --destroy before shutting down Docker / Rancher Desktop, then re-bootstrap on next use. This avoids IP drift entirely.

  • Cluster recreate (last resort): if the API server cert does not cover the new IP, recreate the cluster:

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    ./scripts/bootstrap-local.sh --destroy
./scripts/bootstrap-local.sh --full