OpenShift Container Platform

Override storage or partition setup

You can use a MachineConfig object to change the disk partition schema, file systems, and RAID configurations that were established during the cluster installation. This allows you to make specific configuration changes that are different from the initial cluster state.

If you specified storage and partition configuration upon cluster installation by using a Butane config, Ignition config, or machine config, those configurations become defaults within your cluster. If you create new nodes, those nodes automatically use those default configurations.

You cannot change these components directly. By default, the Machine Config Operator (MCO) reviews changes in MachineConfig objects for specific fields and blocks some changes for security reasons. However, you can override this restriction for disk partition schema, file systems, and RAID configurations by adding the irreconcilableValidationOverrides parameter to the MachineConfiguration object. Then, you can create a new machine config to make the necessary changes for new nodes.

Configuration changes made through this process apply to new nodes only.

For example, you might want to override your default storage configuration to add new hardware that uses a different storage partitioning schema or storage file system to your cluster. In this case, you can modify the storage configuration for any new nodes in your cluster.

Or, if you used Ignition to modify the storage configuration as a post-installation task, your cluster might be reporting an irreconcilableChanges status in the MachineConfigNode object status fields. This messaging can alert you to these differences, so that you can determine if you want new hardware with the new configurations.

Overriding irreconcilable fields is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.

For more information about the support scope of Red Hat Technology Preview features, see Technology Preview Features Support Scope.

Prerequisites

You enabled the required Technology Preview features for your cluster by adding the TechPreviewNoUpgrade feature set to the FeatureGate CR named cluster. For information about enabling Feature Gates, see Enabling features using feature gates.

Enabling the TechPreviewNoUpgrade feature set on your cluster cannot be undone and prevents minor version updates. This feature set allows you to enable these Technology Preview features on test clusters, where you can fully test them. Do not enable this feature set on production clusters.

Procedure

Edit the MachineConfiguration object by using the following command:
```
$ oc edit machineconfiguration
```
Add the irreconcilableValidationOverrides stanza to the MachineConfiguration object.
```
apiVersion: operator.openshift.io/v1
kind: MachineConfiguration
# ...
spec:
  irreconcilableValidationOverrides:
    storage:
    - Disks
    - Raid
    - FileSystems
# ...
```
where:

spec.irreconcilableValidationOverrides.storage.Disks

Allows you to modify the installed storage disk configuration to be used with new nodes. This field is optional.

spec.irreconcilableValidationOverrides.storage.Raid

Allows you to modify the installed RAID configuration to be used with new nodes. This field is optional.

spec.irreconcilableValidationOverrides.storage.FileSystems

Allows you to modify the installed file system configuration to be used with new nodes. This field is optional.

Create a YAML file for a MachineConfig object with the changes that you need, similar to the following:

apiVersion: machineconfiguration.openshift.io/v1
kind: MachineConfig
metadata:
  labels:
    machineconfiguration.openshift.io/role: worker
  name: extra-disks
spec:
  config:
    ignition:
      version: "3.5.0"
    storage:
      disks:
      - device: "/dev/sdb"
        wipeTable: true
        partitions:
        - label: raid.1.1
          number: 1
          sizeMiB: 1024
          startMiB: 0
      - device: "/dev/sdc"
        wipeTable: true
        partitions:
        - label: raid.1.2
          number: 1
          sizeMiB: 1024
          startMiB: 0
      raid:
      - devices:
        - "/dev/disk/by-partlabel/raid.1.1"
        - "/dev/disk/by-partlabel/raid.1.2"
        level: stripe
        name: data
      filesystems:
      - device: "/dev/md/data"
        path: "/var/lib/data"
        format: ext4
        label: DATA

where:

spec.config.storage.disks: Specifies changes to the installed storage disk configuration in Ignition format. This field is optional.
spec.config.storage.raid: Specifies changes to the installed RAID configuration in Ignition format. This field is optional.
spec.config.storage.filesystems: Specifies changes to the installed file system configuration in Ignition format. This field is optional.

Create the MachineConfig object by using a command similar to the following:
```
$ oc create -f <file_name>.yaml
```
When you create a new node from a machine set with the associated label, the new configurations are applied to the node.