Day 39 - Kubernetes Worker Node Failure Troubleshooting

 Day 39 - Kubernetes Worker Node Failure Troubleshooting

#Day-39
Today I tackled Kubernetes Worker Node Failure Troubleshooting — diagnosing NotReady nodes, fixing kubelet issues, and validating CNI networking at the node level.

Key Learnings (Hands-On Debugging Insights)
1️⃣ Node shows NotReady? → Start with networking.
CNI plugins like Calico / Flannel / Canal drive pod-to-pod and node-to-node communication.
If they fail, your worker nodes fail.
2️⃣ Check the CNI config:
/etc/cni/net.d
Valid config files (e.g., 10-calico.conflist) confirm that networking is correctly installed.
3️⃣ Kubelet = the heartbeat of every worker node.
If kubelet is inactive, activating, or failed, the node cannot communicate with the API Server.
Fixing kubelet = fixing the node.
4️⃣ Deep logs matter:
journalctl -u kubelet
Errors, cert issues, wrong file paths — kubelet logs tell the entire story.
5️⃣ Most kubelet failures = certificate or config issues.
Checking:
/var/lib/kubelet/config.yaml
/etc/kubernetes/pki/
is usually where the real fix happens.
6️⃣ Restart the kubelet and confirm:
sudo service kubelet restart
kubectl get nodes
Healthy worker nodes → smooth scheduling → healthy cluster.

Pro Tip:
Worker node troubleshooting is a mix of networking, kubelet internals, cert validation, and logs.
Mastering this makes you not just a Kubernetes user — but someone who understands cluster internals deeply.
Every NotReady node tells you a story about how Kubernetes is wired.

ReadMore: https://lnkd.in/dXNrJjit