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

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.

During the upgrade process, the Machine Config Operator (MCO) applies the new configuration to your cluster machines. It cordons the number of nodes that is specified by the maxUnavailable field on the machine configuration pool and marks them as unavailable. By default, this value is set to 1. It then applies the new configuration and reboots the machine. If you use Red Hat Enterprise Linux (RHEL) machines as workers, the MCO does not update the kubelet on these machines because you must update the OpenShift API on them first. Because the specification for the new version is applied to the old kubelet, the RHEL machine cannot return to the Ready state. You cannot complete the update until the machines are available. However, the maximum number of nodes that are unavailable is set to ensure that normal cluster operations are likely to continue with that number of machines out of service.

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 4.3 channels will never include an upgrade to a 4.4 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.

OpenShift Container Platform 4.3, which includes the upgrade from the previous 4.2 release, has three upgrade channels to choose from:

  • candidate-4.3

  • fast-4.3

  • stable-4.3

The upgrade channels contain two types of updates:

  1. General Availability Software (or GA) - These versions of OpenShift Container Platform are fully supported and are considered production quality. You may upgrade to the general availability release from either of the fast and stable channels.

  2. Release Candidate Software (or RC) - These versions of OpenShift Container Platform are representative of the eventual general availability release and are available only in the candidate-4.3 channel. The release candidate will contain all the features of the product. You are allowed to upgrade from a release candidate to another release candidate and to upgrade from a previous minor version of OpenShift Container Platform to the current release candidate. Release candidate builds are not supported by Red Hat and you will not be able to upgrade from a release candidate to the general availability release of OpenShift Container Platform. Candidates should be used to test feature acceptance and assist in qualifying the next version of OpenShift Container Platform in your infrastructure.

    Release candidates differ from the nightly builds found on try.openshift.com. You cannot upgrade nightly builds to nightly builds. Nightly builds are available for early access to features but are not upgradable or supported.

For GA versions, the fast and stable channels present a choice between receiving updates as soon as they are available or allowing Red Hat to control the rollout of those updates.

fast-4.3

The fast channel is updated with new 4.3 patch versions as soon as Red Hat declares they are generally available. Use this channel if you wish to receive updates as soon as they are available or for your pre-production environments when participating in the connected customer program. This channel will contain all z-stream (4.3.z) updates but will not suggest upgrades to the next minor release (4.4.z) when the next minor release is available.

stable-4.3

The stable channel will contain updates on a time delay as they are gradually rolled out 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 channel. For patch and CVE fixes this can range from several hours to a day and allows an extra period of assessment in how the software performs. If issues are detected during rollout, upgrades to that version may be blocked in both the fast and stable 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 channel, production systems on the stable channel, and participating in Red Hat’s connected customer program - this 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 to the stable channels.

If issues are discovered with an upgrade between patch levels, Red Hat may withdraw that suggested upgrade for affected versions. A newer patch would become available in the appropriate channels and be suggested for upgrade.

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-4.3 channel:

  • 4.3.0

  • 4.3.1

  • 4.3.3

  • 4.3.4

The service only recommends upgrades that have been tested and have no known issues. If you are on 4.3.1 and OpenShift Container Platform is allowing you to select 4.3.4, then it is safe for you to go from .4.3.1 to .4.3.4. Likewise, the absence of 4.3.2 may be due to a CVE that was fixed in 4.3.3 and Red Hat no longer suggests upgrading to a known vulnerable version. If an issue is found that results in a new version being retracted from the recommendations, Red Hat will release a new version that is capable of upgrading from all necessary versions, including the retracted version.

Disconnected clusters

Customers which have chosen to not be connected to Red Hat and are curating 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 between the fast and stable channel at any time. Channels only offer suggested upgrades, and will never suggest a dangerous upgrade. If you switch to the candidate channel after installing from a GA version, you will see a warning the current version is not recognized, and you can safely switch back to a GA channel.

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   4.3.0     True        False         158m    Cluster version is 4.3.0
  2. Review the current update channel information and confirm that your channel is set to stable-4.3:

    $ oc get clusterversion -o json|jq ".items[0].spec"
    
    {
      "channel": "stable-4.3",
      "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-4.3",
      "clusterID": "990f7ab8-109b-4c95-8480-2bd1deec55ff",
      "desiredUpdate": {
        "force": false,
        "image": "quay.io/openshift-release-dev/ocp-release@sha256:9c5f0df8b192a0d7b46cd5f6a4da2289c155fd5302dec7954f8f06c878160b8b",
        "version": "4.3.1" (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