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1. Check node is k8s master or worker kubectl get nodes kubectl get node pe-ioc-master03 -o=yaml 2. Check certificate expired: kubeadm certs check-expiration Note: https://kubernetes.io/docs/tasks/administer-cluster/kubeadm/kubeadm-certs/ Folder include configure (/etc/kubernetes/) and certificate file (/etc/kubernetes/pki) 3. Check kubeadm version kubeadm version 4. Restart the kubelet: sudo systemctl daemon-reload sudo systemctl restart kubelet 5. Renew Certificate on master node (run command for each node): kubeadm alpha certs renew all service docker restart

K8s and Docker swarm both of them are efficient solution for: Massive scale application deployment Implementation Management 👉Key difference: Kubernet (K8S) Docker swarm Container orchestration system that manages multiple containers   Does not manage any containers but instead is a cluster manager for Docker containers. Designed to work with any programming language and framework . Only works with the Docker Engine API. Runs on top of Linux Containers Runs inside Docker Containers. Master-slave architecture. Uses an active/passive model where each worker instance is controlled by its own master instance. Key components of Docker swarm architecture Docker Node, Docker Services, and Docker tasks More complex to set up in the beginning Requires less setup and configuration Support GUI No GUI support