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Chapter 2. Updating clusters overview

You can update an OpenShift Container Platform 4 cluster with a single operation by using the web console or the OpenShift CLI (oc).

2.1. Understanding OpenShift Container Platform updates

About the OpenShift Update Service: For clusters with internet access, Red Hat provides over-the-air updates by using an OpenShift Container Platform update service as a hosted service located behind public APIs.

2.2. Understanding upgrading channels and releases

Upgrading channels and releases: With upgrade channels, you can choose an upgrade strategy. Upgrade channels are specific to a minor version of OpenShift Container Platform. Upgrade channels only control release selection and do not impact the version of the cluster that you install. The openshift-install binary file for a specific version of the OpenShift Container Platform always installs that minor version. For more information, see the following:

2.3. Understanding cluster Operator condition types

The status of cluster Operators includes their condition type, informing you of the current state of your Operator’s health. The following definitions cover a list of some common ClusterOperator condition types. Operators that have additional condition types and use Operator-specific language have been omitted.

The Cluster Version Operator (CVO) is responsible for collecting the status conditions from cluster Operators so that cluster administrators can better understand the state of the OpenShift Container Platform cluster.

  • Available: An Operator with the condition type Available is functional and available in the cluster. If the status is False, at least one part of the operand is non-functional and the condition requires an administrator to intervene.

  • Progressing: An Operator with the condition type Progressing is actively rolling out new code, propagating configuration changes, or otherwise moving from one steady state to another.

    Operators do not report the condition type Progressing as True when they are reconciling a previous known state. If the observed cluster state has changed and the Operator is reacting to it, then the status will report back as True, since it is moving from one steady state to another.

  • Degraded: An Operator with the condition type Degraded has a current state that does not match the required state over a period of time. The period of time can vary by component, but a Degraded state represents persistent observation of an Operator’s condition. As a result, an Operator will not fluctuate in and out of the Degraded state.

    There might be a different condition type if the transition from one state to another does not persist over a long enough period to report Degraded. An Operator will not report Degraded during the course of a normal upgrade. An Operator may report Degraded in response to a persistent infrastructure failure that requires eventual administrator intervention.

    Note

    This condition type is only an indication that something may need investigation and adjustment. As long as the Operator is available, the Degraded condition does not cause user workload failure or application downtime.

  • Upgradeable: An Operator with the condition type Upgradeable indicates whether the Operator is safe to upgrade based on the current cluster state. The message field will contain a human-readable description of what the administrator needs to do for the cluster to successfully update. The CVO allows updates when this condition is True, Unknown or missing.

    When the Upgradeable status is False, only minor updates are impacted, and the CVO prevents the cluster from performing impacted updates unless forced.

2.4. Preparing to perform an EUS-to-EUS update

Preparing to perform an EUS-to-EUS update: Due to fundamental Kubernetes design, all OpenShift Container Platform updates between minor versions must be serialized. You must update from OpenShift Container Platform 4.8 to 4.9, and then to 4.10. You cannot update from OpenShift Container Platform 4.8 to 4.10 directly. However, if you want to update between two Extended Update Support (EUS) versions, you can do so by incurring only a single reboot of non-control plane hosts. For more information, see the following:

2.5. Updating a cluster using the web console

Updating a cluster within a minor version using the web console: You can update an OpenShift Container Platform cluster by using the web console. The following steps update a cluster within a minor version. You can use the same instructions for updating a cluster between minor versions.

2.6. Updating a cluster within a minor version using the command-line interface (CLI)

Updating a cluster within a minor version using the CLI: You can update an OpenShift Container Platform cluster within a minor version by using the OpenShift CLI (oc). The following steps update a cluster within a minor version. You can use the same instructions for updating a cluster between minor versions.

2.7. Performing a canary rollout update

Performing a canary rollout update: By controlling the rollout of an update to the worker nodes, you can ensure that mission-critical applications stay available during the whole update, even if the update process causes your applications to fail. Depending on your organizational needs, you might want to update a small subset of worker nodes, evaluate cluster and workload health over a period of time, and then update the remaining nodes. This is referred to as a canary update. Alternatively, you might also want to fit worker node updates, which often requires a host reboot, into smaller defined maintenance windows when it is not possible to take a large maintenance window to update the entire cluster at one time. You can perform the following procedures:

2.8. Updating a cluster that includes RHEL compute machines

Updating a cluster that includes RHEL compute machines: If your cluster contains Red Hat Enterprise Linux (RHEL) machines, you must perform additional steps to update those machines. You can perform the following procedures:

2.9. Updating a cluster in a disconnected environment

About cluster updates in a disconnected environment: If your mirror host cannot access both the internet and the cluster, you can mirror the images to a file system that is disconnected from that environment. You can then bring that host or removable media across that gap. If the local container registry and the cluster are connected to the mirror host of a registry, you can directly push the release images to the local registry.

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