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Updating hosted control planes - Performing a cluster update | Updating clusters | OKD 4
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Updating hosted control planes

On hosted control planes for OKD, updates are decoupled between the control plane and the nodes. Your service cluster provider, which is the user that hosts the cluster control planes, can manage the updates as needed. The hosted cluster handles control plane updates, and node pools handle node updates.

Updates for the hosted cluster

The spec.release value dictates the version of the control plane. The HostedCluster object transmits the intended spec.release value to the HostedControlPlane.spec.release value and runs the appropriate Control Plane Operator version.

The hosted control plane manages the rollout of the new version of the control plane components along with any OKD components through the new version of the Cluster Version Operator (CVO).

Updates for node pools

With node pools, you can configure the software that is running in the nodes by exposing the spec.release and spec.config values. You can start a rolling node pool update in the following ways:

  • Changing the spec.release or spec.config values.

  • Changing any platform-specific field, such as the AWS instance type. The result is a set of new instances with the new type.

  • Changing the cluster configuration, if the change propagates to the node.

Node pools support replace updates and in-place updates. The nodepool.spec.release value dictates the version of any particular node pool. A NodePool object completes a replace or an in-place rolling update according to the .spec.management.upgradeType value.

After you create a node pool, you cannot change the update type. If you want to change the update type, you must create a node pool and delete the other one.

Replace updates for node pools

A replace update creates instances in the new version while it removes old instances from the previous version. This update type is effective in cloud environments where this level of immutability is cost effective.

Replace updates do not preserve any manual changes because the node is entirely re-provisioned.

In place updates for node pools

An in-place update directly updates the operating systems of the instances. This type is suitable for environments where the infrastructure constraints are higher, such as bare metal.

In-place updates can preserve manual changes, but will report errors if you make manual changes to any file system or operating system configuration that the cluster directly manages, such as kubelet certificates.

Configuring node pools for hosted control planes

On hosted control planes, you can configure node pools by creating a MachineConfig object inside of a config map in the management cluster.

Procedure

  1. To create a MachineConfig object inside of a config map in the management cluster, enter the following information:

    apiVersion: v1
kind: ConfigMap
metadata:
  name: <configmap-name>
  namespace: clusters
data:
  config: |
    apiVersion: machineconfiguration.openshift.io/v1
    kind: MachineConfig
    metadata:
      labels:
        machineconfiguration.openshift.io/role: worker
      name: <machineconfig-name>
    spec:
      config:
        ignition:
          version: 3.2.0
        storage:
          files:
          - contents:
              source: data:...
            mode: 420
            overwrite: true
            path: ${PATH} (1)
    1 Sets the path on the node where the MachineConfig object is stored.

  2. After you add the object to the config map, you can apply the config map to the node pool as follows:

    $ oc edit nodepool <nodepool_name> --namespace <hosted_cluster_namespace>
    apiVersion: hypershift.openshift.io/v1alpha1
kind: NodePool
metadata:
# ...
  name: nodepool-1
  namespace: clusters
# ...
spec:
  config:
  - name: ${configmap-name}
# ...