Metal3MachineTemplate

The Metal3MachineTemplate contains following two specification fields:

• nodeReuse: (true/false) Whether the same pool of BareMetalHosts will be re-used during the upgrade/remediation operations. By default set to false, if set to true, CAPM3 Machine controller will pick the same pool of BareMetalHosts that were released while upgrading/remediation - for the next provisioning phase.
• template: is a template containing the data needed to create a Metal3Machine.

Enabling nodeReuse feature

This feature can be desirable and enabled in scenarios such as upgrade or node remediation. For example, the same pool of hosts need to be used after cluster upgrade and no data of secondary storage should be lost. To achieve that:

1. spec.nodeReuse field of Metal3MachineTemplate must be set to True. This tells that we want to reuse the same hosts after the upgrade, or to be exact same BareMetalHosts should be provisioned.

2. spec.template.spec.automatedCleaningMode field of Metal3MachineTemplate must be set to disabled. This tells that we want secondary/hosted storage data to persist even after upgrade.

Above field changes need to be made before you start upgrading your cluster.

Node Reuse flow

When spec.nodeReuse field of Metal3MachineTemplate is set to True, CAPM3 Machine controller:

• Sets infrastructure.cluster.x-k8s.io/node-reuse label to the corresponding CAPI object name (a controlplane.cluster.x-k8s.io object such as KubeadmControlPlane or a MachineDeployment) on the BareMetalHost during deprovisioning;
• Selects the BareMetalHost that contains infrastructure.cluster.x-k8s.io/node-reuse label and matches exact same CAPI object name set in the previous step during next provisioning.

Example Metal3MachineTemplate :

apiVersion: infrastructure.cluster.x-k8s.io/v1beta1
kind: Metal3MachineTemplate
metadata:
  name: m3mt-0
  namespace: metal3
spec:
  nodeReuse: false
  template:
    spec:
      automatedCleaningMode: metadata
      image:
        checksum: http://172.22.0.1/images/UBUNTU_22.04_NODE_IMAGE_K8S_v1.29.0-raw.img.sha256sum
        checksumType: sha256
        format: raw
        url: http://172.22.0.1/images/UBUNTU_22.04_NODE_IMAGE_K8S_v1.29.0-raw.img
      hostSelector:
        matchLabels:
          key1: value1
        matchExpressions:
          key: key2
          operator: in
          values: { ‘abc’, ‘123’, ‘value2’ }
      dataTemplate:
        Name: m3mt-0-metadata