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Update and maintain clusters

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This tutorial describes how cluster operations for Kubernetes clusters can be triggered. Additionally, it provides insights into how to manually or automatically update the Kubernetes version or Operating System version of your cluster.

Overview of possible cluster operations

Section titled “Overview of possible cluster operations”

The STACKIT Cloud Portal offers several cluster operations that can be directly triggered from a cluster’s context menu in the Kubernetes section.

A screenshot of the STACKIT Kubernetes Engine (SKE) main dashboard, listing three Kubernetes clusters. The cluster named "rekjornhdu4" has a Status of "Healthy" and Version 1.20.11. The options menu (vertical ellipsis) for this cluster is open, displaying a list of available actions. These actions, highlighted by a yellow box, are Hibernate, Reconcile, Run maintenance, Rotate credentials, Download Config (for Kubeconfig), and Delete.

Hibernation

Section titled “Hibernation”

SKE supports hibernation of clusters. This is useful to save costs for clusters which are not required to run all the time. Usually this is the case for demo, evaluation, development or test clusters, which could be put to sleep for example, during nighttimes or during weekends.

When hibernating a cluster, the worker nodes and attached volumes of the cluster are terminated, and the allocated resources are returned, i.e. it is a scale to zero worker nodes of the cluster. Therefore, hibernation is an effective way to minimize costs of temporarily unused clusters.

How to hibernate SKE clusters

Section titled “How to hibernate SKE clusters”

In the Kubernetes section in the STACKIT Cloud Portal, navigate to the cluster that you want to hibernate. Open the cluster’s context menu and select Hibernate to manually hibernate the SKE cluster. Manual hibernation requires confirmation to prevent unintended hibernation and downtime of the cluster.

A screenshot of the STACKIT Kubernetes Engine (SKE) cluster list. Only one cluster, "cl-er0ff72a", is visible, with a Status of "Active" and Version 1.28.9. The options menu (vertical ellipsis) for this cluster is open, showing a list of actions. The options are Hibernate, Reconcile, Run maintenance, Start credentials rotation, Kubeconfig (for downloading the configuration file), and Delete. The Reconcile action is highlighted.

How to wake up a hibernated SKE cluster

Section titled “How to wake up a hibernated SKE cluster”

To wake up a hibernated cluster, navigate to the cluster in the SKE Dashboard. Open the cluster’s context menu and select Wake up manually wake up the cluster.

A screenshot from the STACKIT SKE interface showing a confirmation dialog for hibernating a cluster. The dialog box title is "Hibernate rekjornhdu4?" The accompanying explanatory text reads: "Hibernation shuts down all nodes of your cluster while maintaining the configuration. This feature is used to reduce costs once the cluster is not continuously needed." The user has two options: a white button labeled "Cancel" and a prominent yellow button labeled "Hibernate" to proceed with the shutdown.

Confirm to wake up the cluster in the upcoming popup window. Note that waking up a cluster takes several minutes.

Reconciliation

Section titled “Reconciliation”

During reconciliation, Kubernetes ensures that the current state of a resource matches the desired state specified by the user. The reconciliation process is often triggered by events such as creation or modifications of resources.
A reconciliation will be automatically done at least once per day in the configured maintenance time window.

To trigger a manual reconciliation of the Kubernetes cluster, open the cluster’s context menu and select Reconcile.

A screenshot of the Overview page for the SKE cluster named "rekjornhdu4". The page shows general information, including the Status as "Healthy". A section allows for the management of the Kubernetes version. A dropdown menu, highlighted in a yellow box, is currently displaying "1.21.5 - (supported)". The option to save the change is presented by a yellow button labeled "Save," which is highlighted in red, indicating it is the primary action to confirm a version update.

Maintenance

Section titled “Maintenance”

To trigger a manual update of the Kubernetes version, click on the desired cluster in the STACKIT Cloud Portal. Next, click the edit icon in the top right corner of the General section of the cluster overview page. The Kubernetes version is specified in the lower part of the widget.
In the next step, select the target version of the update. This can either be a updated minor or patch version of Kubernetes. The version update starts after confirming the selection by clicking on Save.

A screenshot showing the Maintenance configuration page for an SKE cluster. The settings are grouped under Maintenance Window and Auto Update. The Maintenance Window is set with a Start Time of "20:00" and a Time Zone of "Western European Time (UTC+0h)". Under Auto Update, toggles are set to "Enabled" for both Operating system and Patch Version updates. A notice states: "Automatic updates will not update to preview versions." The page includes two yellow "Save" buttons to confirm the changes.

How to automatically update the Kubernetes and OS version

Section titled “How to automatically update the Kubernetes and OS version”

Within SKE you can configure a maintance window for Kubernetes and Operating System updates. The maintance window is checked daily by SKE and will trigger updates in case a new supported Kubernetes patch version or a new OS version for the worker nodes is available. If auto-update of the operating system version is configured for a cluster, SKE automatically updates the cluster nodes to the latest version of the operating system supported by SKE during the next maintenance window.

To configure a maintance window, navigate to the overview page of your cluster. On the bottom part of the page a Maintenance section is displayed. After clicking on on the edit icon in the top right corner of the widget, you can set a start and end time and the time zone for your maintance window. Additionally, you can configure which version updates (Kubernetes or OS) should be considered by SKE for automatic updates. Prerequisites for this is a more recent version available and that this version is not classified as a preview version.

A screenshot of the STACKIT Kubernetes Engine (SKE) cluster list, showing three clusters. The second cluster, "easke", has a Status of "Hibernated". The options menu (vertical ellipsis) for this hibernated cluster is open. The first action in the context menu is "Wake up", which is highlighted in a yellow box with a sun/gear icon, indicating the action to reactivate the cluster. Other options listed below it are Reconcile, Run maintenance, Rotate credentials, Download Config, and Delete.

Note that for updates of the Kubernetes or the operating system version, the cluster is reconciled which might include a restart of the cluster control plane and rolling update of the worker nodes.

Summary of the two operations

Section titled “Summary of the two operations”

The following table summarizes the support for day two operations. Click here for more information about the different updates types in SKE.

Operation

Auto-update

Forceful update

Manual update

Update Kubernetes version

Patch versions only

Patch versions and consecutive minor versions only

yes

Update Operating System version

yesyesyes

Forceful updates of the operating system version are triggered like for Kubernetes versions if the operating system version of a cluster has an expiration date that is before the start of the next maintenance window.