By default, Kubernetes certificates need to be renewed once a year. Below is a record of one certificate renewal process. 1. Check the Certificates Check the certificate expiration time on a master node: 1 kubeadm certs check-expiration On older cluster versions this command errors out; use: kubeadm alpha certs check-expiration

The idea of the upgrade is: drain the workloads and take the traffic off, then upgrade the control plane nodes first and the worker nodes afterwards. 1. Check the cluster version 1 2 3 4 kubectl version Client Version: version.Info{Major:"1", Minor:"20", GitVersion:"v1.20.4", GitCommit:"e87da0bd6e03ec3fea7933c4b5263d151aafd07c", GitTreeState:"clean", BuildDate:"2021-02-18T16:12:00Z", GoVersion:"go1.15.8", Compiler:"gc", Platform:"linux/amd64"} Server Version: version.

1. CNI Problems Error log 1 2 journalctl -u kubelet ...Unable to update cni config: No networks found in /etc/cni/net.d Because no CNI is installed, you need to remove --network-plugin=cni from the parameters in /var/lib/kubelet/kubeadm-flags.env. 1 2 cat /var/lib/kubelet/kubeadm-flags.env KUBELET_KUBEADM_ARGS="--cgroup-driver=systemd --pod-infra-container-image=k8s.gcr.io/pause:3.1" 2. Node NotReady There can be many reasons for a node being NotReady.

1. Cluster Planning Prepare three hosts: one Master and two Nodes. Operating system: CentOS 7 Specs: 2 Core 4 GB Docker version: 18.06.3 Kubernetes version: 1.15.3 If you are using a purchased cloud host, open the following ports: 1 2 3 4 5 6 7 8 9 10 11 12