Enabling features using FeatureGates - Working with clusters | Nodes

Understanding feature gates
Enabling feature sets at installation
Enabling feature sets using the web console
Enabling feature sets using the CLI

As an administrator, you can use feature gates to enable features that are not part of the default set of features.

Understanding feature gates

You can use the FeatureGate custom resource (CR) to enable specific feature sets in your cluster. A feature set is a collection of OKD features that are not enabled by default.

You can activate the following feature set by using the FeatureGate CR:

TechPreviewNoUpgrade. This feature set is a subset of the current Technology Preview features. This feature set allows you to enable these tech preview features on test clusters, where you can fully test them, while leaving the features disabled on production clusters. Enabling this feature set cannot be undone and prevents minor version updates. This feature set is not recommended on production clusters.

Enabling the TechPreviewNoUpgrade feature set on your cluster cannot be undone and prevents minor version updates. You should not enable this feature set on production clusters.

The following Technology Preview features are enabled by this feature set:
- CSI automatic migration. Enables automatic migration for supported in-tree volume plugins to their equivalent Container Storage Interface (CSI) drivers. Supported for:
  
  Azure File (CSIMigrationAzureFile)
  
  VMware vSphere (CSIMigrationvSphere)
- Shared Resources CSI Driver and Build CSI Volumes in OpenShift Builds. Enables the Container Storage Interface (CSI) (CSIDriverSharedResource).
- CSI volumes. Enables CSI volume support for the OKD build system (BuildCSIVolumes).
- Swap memory on nodes. Enables swap memory use for OKD workloads on a per-node basis (NodeSwap).
- cgroups v2. Enables cgroup v2, the next version of the Linux cgroup API (CGroupsV2).
- crun. Enables the crun container runtime (Crun).
- Insights Operator. Enables the Insights Operator, which gathers OKD configuration data and sends it to Red Hat (InsightsConfigAPI).
- External cloud providers. Enables support for external cloud providers for clusters on vSphere, AWS, Azure, and GCP. Support for OpenStack is GA. (ExternalCloudProvider)
- Pod topology spread constraints. Enables the matchLabelKeys parameter for pod topology contraints. The parameter is list of pod label keys to select the pods over which spreading will be calculated (MatchLabelKeysInPodTopologySpread).

For more information about the features activated by the TechPreviewNoUpgrade feature gate, see the following topics:

Enabling feature sets at installation

You can enable feature sets for all nodes in the cluster by editing the install-config.yaml file before you deploy the cluster.

Prerequisites

You have an install-config.yaml file.

Procedure

Use the featureSet parameter to specify the name of the feature set you want to enable, such as TechPreviewNoUpgrade:

Enabling the TechPreviewNoUpgrade feature set on your cluster cannot be undone and prevents minor version updates. You should not enable this feature set on production clusters.

Sample install-config.yaml file with an enabled feature set

compute:
- hyperthreading: Enabled
  name: worker
  platform:
    aws:
      rootVolume:
        iops: 2000
        size: 500
        type: io1
      metadataService:
        authentication: Optional
      type: c5.4xlarge
      zones:
      - us-west-2c
  replicas: 3
featureSet: TechPreviewNoUpgrade

Save the file and reference it when using the installation program to deploy the cluster.

Verification

You can verify that the feature gates are enabled by looking at the kubelet.conf file on a node after the nodes return to the ready state.

From the Administrator perspective in the web console, navigate to Compute → Nodes.
Select a node.
In the Node details page, click Terminal.
In the terminal window, change your root directory to /host:
```
sh-4.2# chroot /host
```
View the kubelet.conf file:
```
sh-4.2# cat /etc/kubernetes/kubelet.conf
```
Sample output
```
 ...
featureGates:
  InsightsOperatorPullingSCA: true,
  LegacyNodeRoleBehavior: false
 ...
```
The features that are listed as true are enabled on your cluster.

The features listed vary depending upon the OKD version.

Enabling feature sets using the web console

You can use the OKD web console to enable feature sets for all of the nodes in a cluster by editing the FeatureGate custom resource (CR).

Procedure

To enable feature sets:

In the OKD web console, switch to the Administration → Custom Resource Definitions page.
On the Custom Resource Definitions page, click FeatureGate.
On the Custom Resource Definition Details page, click the Instances tab.
Click the cluster feature gate, then click the YAML tab.
Edit the cluster instance to add specific feature sets:

Enabling the TechPreviewNoUpgrade feature set on your cluster cannot be undone and prevents minor version updates. You should not enable this feature set on production clusters.
Sample Feature Gate custom resource
```
apiVersion: config.openshift.io/v1
kind: FeatureGate
metadata:
  name: cluster (1)
....

spec:
  featureSet: TechPreviewNoUpgrade (2)
```
1 The name of the FeatureGate CR must be cluster.

2 Add the feature set that you want to enable:

TechPreviewNoUpgrade enables specific Technology Preview features.
After you save the changes, new machine configs are created, the machine config pools are updated, and scheduling on each node is disabled while the change is being applied.

Verification

You can verify that the feature gates are enabled by looking at the kubelet.conf file on a node after the nodes return to the ready state.

From the Administrator perspective in the web console, navigate to Compute → Nodes.
Select a node.
In the Node details page, click Terminal.
In the terminal window, change your root directory to /host:
```
sh-4.2# chroot /host
```
View the kubelet.conf file:
```
sh-4.2# cat /etc/kubernetes/kubelet.conf
```
Sample output
```
 ...
featureGates:
  InsightsOperatorPullingSCA: true,
  LegacyNodeRoleBehavior: false
 ...
```
The features that are listed as true are enabled on your cluster.

The features listed vary depending upon the OKD version.

Enabling feature sets using the CLI

You can use the OpenShift CLI (oc) to enable feature sets for all of the nodes in a cluster by editing the FeatureGate custom resource (CR).

Prerequisites

You have installed the OpenShift CLI (oc).

Procedure

To enable feature sets:

Edit the FeatureGate CR named cluster:
```
$ oc edit featuregate cluster
```
Enabling the TechPreviewNoUpgrade feature set on your cluster cannot be undone and prevents minor version updates. You should not enable this feature set on production clusters.
Sample FeatureGate custom resource
```
apiVersion: config.openshift.io/v1
kind: FeatureGate
metadata:
  name: cluster (1)
spec:
  featureSet: TechPreviewNoUpgrade (2)
```
1 The name of the FeatureGate CR must be cluster.

2 Add the feature set that you want to enable:

TechPreviewNoUpgrade enables specific Technology Preview features.
After you save the changes, new machine configs are created, the machine config pools are updated, and scheduling on each node is disabled while the change is being applied.

Verification

You can verify that the feature gates are enabled by looking at the kubelet.conf file on a node after the nodes return to the ready state.

From the Administrator perspective in the web console, navigate to Compute → Nodes.
Select a node.
In the Node details page, click Terminal.
In the terminal window, change your root directory to /host:
```
sh-4.2# chroot /host
```
View the kubelet.conf file:
```
sh-4.2# cat /etc/kubernetes/kubelet.conf
```
Sample output
```
 ...
featureGates:
  InsightsOperatorPullingSCA: true,
  LegacyNodeRoleBehavior: false
 ...
```
The features that are listed as true are enabled on your cluster.

The features listed vary depending upon the OKD version.

1	The name of the `FeatureGate` CR must be `cluster`.
2	Add the feature set that you want to enable: `TechPreviewNoUpgrade` enables specific Technology Preview features.

Enabling features using feature gates

Understanding feature gates

Enabling feature sets at installation

Enabling feature sets using the web console

Enabling feature sets using the CLI