Red Hat OpenShift Container Platform

Create a machine config pool for infrastructure machines

You can create a machine configuration pool for infrastructure machines to apply dedicated configuration to infra machines. You might want to apply dedicated configuration to infra machines because they run distinct workloads from other nodes in the cluster.

Creating a custom machine configuration pool overrides default worker pool configurations if they refer to the same file or unit.

Procedure

Add a label to the node you want to assign as the infra node by running the following command:
```
$ oc label node <node_name> node-role.kubernetes.io/infra=
```
where:

<node_name>

Specifies the name of the node you want to assign as an infra node.

Create a YAML file that defines the machine config pool, as in the following example:

apiVersion: machineconfiguration.openshift.io/v1
kind: MachineConfigPool
metadata:
  name: infra
spec:
  machineConfigSelector:
    matchExpressions:
      - {key: machineconfiguration.openshift.io/role, operator: In, values: [worker,infra]}
  nodeSelector:
    matchLabels:
      node-role.kubernetes.io/infra: ""

Add the worker role and your custom role in the spec.machineConfigSelector.matchExpressions[] field.

Add the label you added to the node in the spec.nodeSelector.matchLabels field.

Custom machine config pools inherit machine configs from the worker pool. Custom pools use any machine config targeted for the worker pool, but add the ability to also deploy changes that are targeted at only the custom pool. Because a custom pool inherits resources from the worker pool, any change to the worker pool also affects the custom pool.

After you have the YAML file, you can create the machine config pool by specifying the file you created in the following command:
```
$ oc create -f <filename>
```

Check the machine configs to ensure that the infrastructure configuration rendered successfully by running the following command:

$ oc get machineconfig

Example output

NAME                                                        GENERATEDBYCONTROLLER                      IGNITIONVERSION   CREATED
00-master                                                   365c1cfd14de5b0e3b85e0fc815b0060f36ab955   3.5.0             31d
00-worker                                                   365c1cfd14de5b0e3b85e0fc815b0060f36ab955   3.5.0             31d
# ...
rendered-infra-4e48906dca84ee702959c71a53ee80e7             365c1cfd14de5b0e3b85e0fc815b0060f36ab955   3.5.0             23m

You should see a new machine config, with the rendered-infra-* prefix.

Optional: To deploy changes to a custom pool, create a machine config that uses the custom pool name as the label, such as infra. Note that this is not required and only shown for instructional purposes. In this manner, you can apply any custom configurations specific to only your infra nodes.

After you create the new machine config pool, the MCO generates a new rendered config for that pool, and associated nodes of that pool reboot to apply the new configuration.
1. Create a YAML file that defines the machine config pool, as in the following example:
  $ cat infra.mc.yaml
  Example output
  apiVersion: machineconfiguration.openshift.io/v1 kind: MachineConfig metadata: name: 51-infra labels: machineconfiguration.openshift.io/role: <role> spec: config: ignition: version: 3.5.0 storage: files: - path: /etc/infratest mode: 0644 contents: source: data:,infra
  where:
  
  role
  
  Specifies the label you added to the node as a nodeSelector.
2. Apply the machine config to the infra-labeled nodes by running the following command:
  $ oc create -f infra.mc.yaml

Confirm that your new machine config pool is available by running the following command:

$ oc get mcp

Example output

NAME     CONFIG                                             UPDATED   UPDATING   DEGRADED   MACHINECOUNT   READYMACHINECOUNT   UPDATEDMACHINECOUNT   DEGRADEDMACHINECOUNT   AGE
infra    rendered-infra-60e35c2e99f42d976e084fa94da4d0fc    True      False      False      1              1                   1                     0                      4m20s
master   rendered-master-9360fdb895d4c131c7c4bebbae099c90   True      False      False      3              3                   3                     0                      91m
worker   rendered-worker-60e35c2e99f42d976e084fa94da4d0fc   True      False      False      2              2                   2                     0                      91m

In this example, the role of the node was changes from worker to infra.