3 min read | by Jordi Prats
A kubernetes cluster can get outdated pretty soon since Kubernetes keeps evolving at every release. If we have a k3s cluster we can use the system-upgrade-controller for automatically handling the upgrades. Let's take a look on how to configure it
We can install the system-upgrade-controller by going to the releases page and looking for the yaml file attached to the release. It will install a deployment that uses a service-account, a clusterRoleBinding, and a configmap. At the time of this writing the latest release is v0.6.2 so to install it you would go like this:
$ kubectl apply -f https://github.com/rancher/system-upgrade-controller/releases/download/v0.6.2/system-upgrade-controller.yaml namespace/system-upgrade created serviceaccount/system-upgrade created clusterrolebinding.rbac.authorization.k8s.io/system-upgrade created configmap/default-controller-env created deployment.apps/system-upgrade-controller created Once it is installed we just need to create the update plans to configure it. If we want to use the release channel to update the cluster as soon as they the releases are tagged as stable we just needs to set the following:
# Server plan apiVersion: upgrade.cattle.io/v1 kind: Plan metadata: name: server-plan namespace: system-upgrade spec: concurrency: 1 cordon: true nodeSelector: matchExpressions: - key: node-role.kubernetes.io/master operator: In values: - "true" serviceAccountName: system-upgrade upgrade: image: rancher/k3s-upgrade channel: https://update.k3s.io/v1-release/channels/stable --- # Agent plan apiVersion: upgrade.cattle.io/v1 kind: Plan metadata: name: agent-plan namespace: system-upgrade spec: concurrency: 1 cordon: true nodeSelector: matchExpressions: - key: node-role.kubernetes.io/master operator: DoesNotExist prepare: args: - prepare - server-plan image: rancher/k3s-upgrade serviceAccountName: system-upgrade upgrade: image: rancher/k3s-upgrade channel: https://update.k3s.io/v1-release/channels/stable If you take a look at the k3s releases you will be able to see that not every release goes straight to the release channel, meaning that your cluster won't be updated to the cutting edge version which feels a lot safer:
As v1.21 releases include a number of significant changes from previous versions, we will not make v1.21 available via the stable release channel until a later date.
On the other hand, if you want to update the cluster to a specific version you can also do it using the system-upgrade-controller. Instead of setting a channel you'll have to specify the version tag you want to use:
# Server plan apiVersion: upgrade.cattle.io/v1 kind: Plan metadata: name: server-plan namespace: system-upgrade spec: concurrency: 1 cordon: true nodeSelector: matchExpressions: - key: node-role.kubernetes.io/master operator: In values: - "true" serviceAccountName: system-upgrade upgrade: image: rancher/k3s-upgrade version: v1.21.0+k3s1 --- # Agent plan apiVersion: upgrade.cattle.io/v1 kind: Plan metadata: name: agent-plan namespace: system-upgrade spec: concurrency: 1 cordon: true nodeSelector: matchExpressions: - key: node-role.kubernetes.io/master operator: DoesNotExist prepare: args: - prepare - server-plan image: rancher/k3s-upgrade serviceAccountName: system-upgrade upgrade: image: rancher/k3s-upgrade version: v1.21.0+k3s1 Posted on 26/05/2021