How to upgrade a MicroK8s cluster

For this tutorial, we'll use a 3-node MicroK8s cluster with nodes k8s-1, k8s-2, and k8s-3. microk8s kubectl get nodes Enter fullscreen mode Exit fullscreen mode NAME STATUS ROLES AGE VERSION k8s-1 Ready 142d v1.35.6 k8s-2 Ready 142d v1.35.6 k8s-3 Ready 142d v1.35.6 Enter fullscreen mode Exit fullscreen mode Upgrade the first node To upgrade a node, we must cordon it first so new pods cannot be scheduled on it. microk8s kubectl cordon k8s-1 Enter fullscreen mode Exit fullscreen mode node/k8s-1 cordoned Enter fullscreen mode Exit fullscreen mode If we get the node list again, we can see that it now has pod scheduling disabled. microk8s kubectl get nodes Enter fullscreen mode Exit fullscreen mode NAME STATUS ROLES AGE VERSION k8s-1 Ready,SchedulingDisabled 142d v1.35.6 k8s-2 Ready 142d v1.35.6 k8s-3 Ready 142d v1.35.6 Enter fullscreen mode Exit fullscreen mode Next, we must remove the remaining pods on this node by draining it. microk8s kubectl drain k8s-1 --ignore-daemonsets --delete-emptydir-data Enter fullscreen mode Exit fullscreen mode node/k8s-1 already cordoned Warning: ignoring DaemonSet-managed Pods: ingress/traefik-zgvnx, kube-system/calico-node-2nlwf evicting pod sertxudev/sertxudev-worker-86d556b9cd-f5nhw evicting pod postgresql/postgresql-cluster-3 evicting pod sertxudev/sertxudev-app-7d46bdbbcc-977lf evicting pod sertxudev/sertxudev-scheduler-5996645758-8fsht pod/postgresql-cluster-3 evicted Enter fullscreen mode Exit fullscreen mode We can check that our node no longer has pods, except from the required base ones. microk8s kubectl get pods -A --field-selector spec.nodeName=k8s-1 Enter fullscreen mode Exit fullscreen mode NAMESPACE NAME READY STATUS RESTARTS AGE ingress traefik-zgvnx 1/1 Running 0 142d kube-system calico-node-2nlwf 1/1 Running 0 17d Enter fullscreen mode Exit fullscreen mode Now that our node is empty, we can proceed with the upgrade. It's recommended to upgrade one minor version at a time. You can review the latest MicroK8s version on GitHub releases . Ensure you're connected to the node you want to upgrade. Previous commands can be run from any K8s node, but snap refresh should be run in the node you want to upgrade. snap refresh microk8s --channel 1.36/stable Enter fullscreen mode Exit fullscreen mode microk8s (1.36/stable) v1.36.2 from Canonical✓ refreshed Enter fullscreen mode Exit fullscreen mode Once the MicroK8s snap has been upgraded, we can let K8s start creating pods in our node by uncordoning it. microk8s kubectl uncordon k8s-1 Enter fullscreen mode Exit fullscreen mode node/k8s-1 uncordoned Enter fullscreen mode Exit fullscreen mode If we check the cluster nodes again, we can see that our current node has been updated. kubectl get nodes Enter fullscreen mode Exit fullscreen mode NAME STATUS ROLES AGE VERSION k8s-1 Ready 142d v1.36.2 k8s-2 Ready 142d v1.35.6 k8s-3 Ready 142d v1.35.6 Enter fullscreen mode Exit fullscreen mode Once the upgraded node is ready to receive pods again, we can begin to upgrade the next node. By running the same commands we've just seen for the next node until all nodes are upgraded. Rebalance deployments Once our cluster is up-to-date, we might want to rebalance our deployments so pods are spread among all nodes. kubectl get nodes Enter fullscreen mode Exit fullscreen mode NAME STATUS ROLES AGE VERSION k8s-1 Ready 142d v1.36.2 k8s-2 Ready 142d v1.36.2 k8s-3 Ready 142d v1.36.2 Enter fullscreen mode Exit fullscreen mode First, we should get the deployments that our cluster hosts. microk8s kubectl get deployments -A Enter fullscreen mode Exit fullscreen mode NAMESPACE NAME READY UP-TO-DATE AVAILABLE AGE cert-manager cert-manager 1/1 1 1 441d cert-manager cert-manager-cainjector 1/1 1 1 441d cert-manager cert-manager-webhook 1/1 1 1 441d cnpg-system barman-cloud 1/1 1 1 333d cnpg-system cnpg-controller-manager 1/1 1 1 333d kube-system calico-kube-controllers 1/1 1 1 454d kube-system coredns 1/1 1 1 454d kube-system hostpath-provisioner 1/1 1 1 448d kube-system metrics-server 1/1 1 1 444d sertxudev sertxudev-app 2/2 2 2 200d sertxudev sertxudev-scheduler 1/1 1 1 420d sertxudev sertxudev-worker 1/1 1 1 420d Enter fullscreen mode Exit fullscreen mode Next, we restart the rollout of each deployment we want to rebalance. kubectl rollout restart deployment -n sertxudev sertxudev-app kubectl rollout restart deployment -n sertxudev sertxudev-scheduler kubectl rollout restart deployment -n sertxudev sertxudev-worker Enter fullscreen mode Exit fullscreen mode deployment.apps/sertxudev-app restarted deployment.apps/sertxudev-scheduler restarted deployment.apps/sertxudev-worker restarted Enter fullscreen mode Exit fullscreen mode Now we have an up-to-date MicroK8s cluster ready to continue serving traffic as usual.