You can update, or upgrade, an OpenShift Container Platform cluster within a minor version by using the OpenShift CLI (oc).

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.

Understanding OpenShift Container Platform upgrade channels

In OpenShift Container Platform 4.1, Red Hat introduced the concept of upgrade channels for recommending the appropriate upgrade versions to your cluster. Upgrade channels separate upgrade strategies and also are used to control the cadence of updates. Channels are tied to a minor version of OpenShift Container Platform. For instance, OpenShift Container Platform 4.2 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. Channels only control updates 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.

See OpenShift 4.2 Upgrades phased roll out for more information on the types of updates and upgrade channels.

Updating a cluster by using the CLI

If updates are available, you can update your cluster by using the OpenShift CLI (oc).

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

Prerequisites
  • Install the version of the OpenShift Command-line Interface (CLI), commonly known as oc, that matches the version for your updated version.

  • Log in to the cluster as user with cluster-admin privileges.

  • Install the jq package.

Procedure
  1. Ensure that your cluster is available:

    $ oc get clusterversion
    
    NAME      VERSION   AVAILABLE   PROGRESSING   SINCE   STATUS
    version   4.2.0     True        False         158m    Cluster version is 4.2.0
  2. Review the current update channel information and confirm that your channel is set to stable-4.2:

    $ oc get clusterversion -o json|jq ".items[0].spec"
    
    {
      "channel": "stable-4.2",
      "clusterID": "990f7ab8-109b-4c95-8480-2bd1deec55ff",
      "upstream": "https://api.openshift.com/api/upgrades_info/v1/graph"
    }

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

  3. View the available updates and note the version number of the update that you want to apply:

    $ oc adm upgrade
    
    Cluster version is 4.1.0
    
    Updates:
    
    VERSION IMAGE
    4.1.2   quay.io/openshift-release-dev/ocp-release@sha256:9c5f0df8b192a0d7b46cd5f6a4da2289c155fd5302dec7954f8f06c878160b8b
  4. Apply an update:

    • To update to the latest version:

      $ oc adm upgrade --to-latest=true (1)
    • To update to a specific version:

      $ oc adm upgrade --to=<version> (1)
      1 <version> is the update version that you obtained from the output of the previous command.
  5. Review the status of the Cluster Version Operator:

    $ oc get clusterversion -o json|jq ".items[0].spec"
    
    {
      "channel": "stable-4.2",
      "clusterID": "990f7ab8-109b-4c95-8480-2bd1deec55ff",
      "desiredUpdate": {
        "force": false,
        "image": "quay.io/openshift-release-dev/ocp-release@sha256:9c5f0df8b192a0d7b46cd5f6a4da2289c155fd5302dec7954f8f06c878160b8b",
        "version": "4.2.1" (1)
      },
      "upstream": "https://api.openshift.com/api/upgrades_info/v1/graph"
    }
    1 If the version number in the desiredUpdate stanza matches the value that you specified, the update is in progress.
  6. Review the cluster version status history to monitor the status of the update. It might take some time for all the objects to finish updating.

    $ oc get clusterversion -o json|jq ".items[0].status.history"
    
    [
      {
        "completionTime": null,
        "image": "quay.io/openshift-release-dev/ocp-release@sha256:9c5f0df8b192a0d7b46cd5f6a4da2289c155fd5302dec7954f8f06c878160b8b",
        "startedTime": "2019-06-19T20:30:50Z",
        "state": "Partial",
        "verified": true,
        "version": "4.1.2"
      },
      {
        "completionTime": "2019-06-19T20:30:50Z",
        "image": "quay.io/openshift-release-dev/ocp-release@sha256:b8307ac0f3ec4ac86c3f3b52846425205022da52c16f56ec31cbe428501001d6",
        "startedTime": "2019-06-19T17:38:10Z",
        "state": "Completed",
        "verified": false,
        "version": "4.1.0"
      }
    ]

    The history contains a list of the most recent versions applied to the cluster. This value is updated when the CVO applies an update. The list is ordered by date, where the newest update is first in the list. Updates in the history have state Completed if the rollout completed and Partial if the update failed or did not complete.

    If an upgrade fails, the Operator stops and reports the status of the failing component. Rolling your cluster back to a previous version is not supported. If your upgrade fails, contact Red Hat support.

  7. After the update completes, you can confirm that the cluster version has updated to the new version:

    $ oc get clusterversion
    
    NAME      VERSION     AVAILABLE   PROGRESSING   SINCE     STATUS
    version   4.1.2       True        False         2m        Cluster version is 4.1.2