You can update, or upgrade, an OpenShift Container Platform cluster between minor versions.

Because of the difficulty of changing update channels by using oc, use the web console to change the update channel. It is recommended to complete the update process within the web console. You can follow the steps in Updating a cluster within a minor version by using the CLI to complete the update after you change to a 4.2 channel.

Prerequisites

About the OpenShift Container Platform update service

The OpenShift Container Platform update service is the hosted service that provides over-the-air updates to both OpenShift Container Platform and Red Hat Enterprise Linux CoreOS (RHCOS). It provides a graph, or diagram that contain vertices and the edges that connect them, of component Operators. The edges in the graph show which versions you can safely update to, and the vertices are update payloads that specify the intended state of the managed cluster components.

The Cluster Version Operator (CVO) in your cluster checks with the OpenShift Container Platform update service to see the valid updates and update paths based on current component versions and information in the graph. When you request an update, the OpenShift Container Platform CVO uses the release image for that update to upgrade your cluster. The release artifacts are hosted in Quay as container images.

To allow the OpenShift Container Platform update service to provide only compatible updates, a release verification pipeline exists to drive automation. Each release artifact is verified for compatibility with supported cloud platforms and system architectures as well as other component packages. After the pipeline confirms the suitability of a release, the OpenShift Container Platform update service notifies you that it is available.

Because the update service displays all valid updates, you must not force an update to a version that the update service does not display.

During continuous update mode, two controllers run. One continuously updates the payload manifests, applies them to the cluster, and outputs the status of the controlled rollout of the Operators, whether they are available, upgrading, or failed. The second controller polls the OpenShift Container Platform update service to determine if updates are available.

Reverting your cluster to a previous version, or a rollback, is not supported. Only upgrading to a newer version is supported.

OpenShift Container Platform Upgrade Channels and Releases

In OpenShift Container Platform 4.1, Red Hat introduced the concept of channels for recommending the appropriate release versions for cluster upgrade. By controlling the pace of upgrades, these upgrade channels allow users to choose an upgrade strategy. Upgrade channels are tied to a minor version of OpenShift Container Platform. For instance, OpenShift Container Platform 4.2 upgrade channels will never include an upgrade to a 4.3 release. This ensures administrators make an explicit decision to upgrade to the next minor version of OpenShift Container Platform. Upgrade channels only control release selection and have no impact on the version of the cluster you install; the openshift-install binary for a given patch level of OpenShift Container Platform always installs that patch level.

OpenShift Container Platform 4.2 has the following upgrade channels to choose from:

  • candidate-4.2

  • fast-4.2

  • stable-4.2

candidate-4.2 Channel

The candidate-4.2 channel will contain candidate builds for a z-stream (4.2.z) release. Release candidates contain all the features of the product but they are not supported and should only be used to test feature acceptance and assist in qualifying the next version of OpenShift Container Platform. A release candidate is any build (e.g. 4.2.0-rc.3, 4.2.0) that is available in the candidate channel. After a version lands in the candidate channel, it goes through more quality checks and if it meets the quality standard it is promoted to fast-4.2 or stable-4.2 channels. So if a given release is available in the candidate-4.2 channel and also in the fast-4.2 or stable-4.2 channels, it is a Red Hat supported version. Additionally candidate-4.2 may include dead end releases from which there are no or ever be recommended upgrades.

The candidate-4.2 channel also allows upgrading from a previous minor version of OpenShift Container Platform to 4.2.

Release candidates differ from the nightly builds found on try.openshift.com. Nightly builds are available for early access to features but updating to or from nightly builds is neither recommended nor supported. Nightly builds are not avilable in any upgrade channel.

fast-4.2 Channel

The fast-4.2 channel is updated with new 4.2 patch versions as soon as Red Hat declares the given patch as a general availability release. As such, these releases are fully supported, are production quality and have performed well while available as a release candidate in the candidate-4.2 channel from where they were promoted. Some time after a release appears in fast-4.2 it will also appear in stable-4.2. Releases will never appear in stable-4.2 before they appear in fast-4.2.

The fast-4.2 channel also allows upgrading from a previous minor version of OpenShift Container Platform.

stable-4.2 Channel

Like the fast-4.2 channel, the stable-4.2 channel will only contain releases that have been declared general availability are therefore fully supported. However the stable-4.2 channel will gradually roll out releases to customers based on data from our SRE teams, support services, and pre-production and production environments that participate in our connected customer program, rather than being immediately available as they are in the fast-4.2 channel. For patch and CVE fixes this delay can range from several hours to a day and allows an extra period of assessment in how the software performs.

The stable-4.2 channel also allows upgrading from a previous minor version of OpenShift Container Platform.

Upgrade Version Paths

OpenShift Container Platform maintains an upgrade recommendation service that understands the version of OpenShift Container Platform you have installed as well as the path to take within the channel you choose to get you to the next release. You can imagine seeing the following in the fast-4.2 channel:

  • 4.2.0

  • 4.2.1

  • 4.2.3

  • 4.2.4

The service only recommends upgrades that have been tested and have no serious issues. If you are on 4.2.1 and OpenShift Container Platform is allowing you to select 4.2.4, then it is safe for you to go from .4.2.1 to .4.2.4. Likewise, the absence of 4.2.2 may be due to a CVE that was fixed in 4.2.3 and Red Hat no longer suggests upgrading to a known vulnerable version.

Update stability depends on your channel. The presence of an update recommendation in the candidate-4.2 channel does not imply that the update is supported. It means that no serious issues have been found with the update yet, but there may not be significant traffic through the update to suggest stability. The presence of an update recommendation in the fast-4.2 or stable-4.2 channels is a declaration that the update is fully supported while it is in the channel. While releases will never be removed from a channel, update recommendations which exhibit serious issues will be removed from all channels. Updates initiated after the update recommendation has been removed may not be supported.

Red Hat will eventually provide supported update paths from any supported (fast-4.2 or stable-4.2) release to the latest release in 4.2.z, although there may be delays while safe paths away from troubled releases are constructed and verified.

Fast and Stable Channel Usage and Strategies

The fast-4.2 and stable-4.2 channels present a choice between receiving general availability releases as soon as they are available or allowing Red Hat to control the rollout of those updates. If issues are detected during rollout or at a later time, upgrades to that version may be blocked in both the fast-4.2 and stable-4.2 channels, and a new version may be introduced that will be the new preferred upgrade target.

Customers can improve this process by configuring pre-production systems on the fast-4.2 channel, production systems on the stable-4.2 channel, and participating in Red Hat’s connected customer program. This program allows Red Hat to observe the impact of updates on your specific hardware and software configurations. Future releases may improve or alter the pace at which updates move from the fast-4.2 to the stable-4.2 channel.

Restricted Network Clusters

Customers who have chosen to not be connected to Red Hat and are controlling their own OpenShift Container Platform container image content manually should consult the Red Hat errata associated with product releases and note any comments impacting upgrades. During upgrade the user interface may caution about switching between these versions and it is up to the customer to ensure they have correctly selected the appropriate version before bypassing those cautions.

Switching Between Channels

It is supported for customers to switch from the stable-4.2 channel to the fast-4.2 at any time. Customers can also switch to the candidate-4.2 at any time but should be aware that some releases in the candidate-4.2 channel may be release candidates and therefore not supported. A customer can switch from candidate-4.2 to fast-4.2 if their current release is a general availability release. Customers can always switch from fast-4.2 to stable-4.2, although there may be a delay of up to a day if their current release was recently promoted to fast-{product-stable} while they wait for the release to be promoted to stable-4.2. If you change to a channel that does not include your current release, an alert will fire, no updates will be recommended, and you can safely change back to your original channel at any point.

Please refer to the candidate-4.2 Channel section above to understand the distinction between a release candidate and a general avilability release.

Updating a cluster by using the web console

If updates are available, you can update your cluster from the web console.

You can find information about available OpenShift Container Platform advisories and updates in the errata section of the Customer Portal.

Prerequisites
  • Have access to the web console as a user with admin privileges.

Procedure
  1. From the web console, click Administration > Cluster Settings and review the contents of the Overview tab.

  2. For production clusters, ensure that the CHANNEL is set to the correct channel for your current minor version, such as stable-4.2.

    For production clusters, you must subscribe to a stable-* or fast-* channel.

    • If the UPDATE STATUS is not Updates Available, you cannot upgrade your cluster.

    • The DESIRED VERSION indicates the cluster version that your cluster is running or is updating to.

  3. Click Updates Available, select the highest available version and click Update. The UPDATE STATUS changes to Updating, and you can review the progress of the Operator upgrades on the Cluster Operators tab.

  4. After the update completes and the Cluster Version Operator refreshes the available updates, check if more updates are available in your current channel.

    • If updates are available, continue to perform updates in the current channel until you can no longer update.

    • If no updates are available, change the CHANNEL to the stable-* or fast-* channel for the next minor version, and update to the version that you want in that channel.

    You might need to perform several intermediate updates until you reach the version that you want.