Configuration Policy

The ConfigurationPolicy defines Kubernetes manifests to compare with objects that currently exist on the cluster. The Configuration policy controller is provided by Open Cluster Management and runs on managed clusters.

Prerequisites

You must meet the following prerequisites to install the configuration policy controller:

  • Ensure kubectl and kustomize are installed.

  • Ensure Golang is installed, if you are planning to install from the source.

  • Ensure the open-cluster-management policy framework is installed. See Policy Framework for more information.

Installing the configuration policy controller

Deploy via Clusteradm CLI

Ensure clusteradm CLI is installed and is newer than v0.3.0. Download and extract the clusteradm binary. For more details see the clusteradm GitHub page.

  1. Deploy the configuration policy controller to the managed clusters (this command is the same for a self-managed hub):

    # Deploy the configuration policy controller
clusteradm addon enable addon --names config-policy-controller --clusters <cluster_name> --context ${CTX_HUB_CLUSTER}

  2. Ensure the pod is running on the managed cluster with the following command:

    $ kubectl get pods -n open-cluster-management-agent-addon
NAME                                               READY   STATUS    RESTARTS   AGE
config-policy-controller-7f8fb64d8c-pmfx4          1/1     Running   0          44s

Deploy from source

  1. Deploy the config-policy-controller to the managed cluster with the following commands:

    # The context name of the clusters in your kubeconfig
# If the clusters are created by KinD, then the context name will the follow the pattern "kind-<cluster name>".
export CTX_HUB_CLUSTER=<your hub cluster context>           # export CTX_HUB_CLUSTER=kind-hub
export CTX_MANAGED_CLUSTER=<your managed cluster context>   # export CTX_MANAGED_CLUSTER=kind-cluster1

# Configure kubectl to point to the managed cluster
kubectl config use-context ${CTX_MANAGED_CLUSTER}

# Create the namespace for the controller
export MANAGED_NAMESPACE="open-cluster-management-agent-addon"
kubectl create ns ${MANAGED_NAMESPACE}

# Apply the CRD
export COMPONENT="config-policy-controller"
export GIT_PATH="https://raw.githubusercontent.com/open-cluster-management-io/${COMPONENT}/v0.12.0/deploy"
kubectl apply -f ${GIT_PATH}/crds/policy.open-cluster-management.io_configurationpolicies.yaml
kubectl apply -f ${GIT_PATH}/crds/policy.open-cluster-management.io_operatorpolicies.yaml

# Set the managed cluster name
export MANAGED_CLUSTER_NAME=<your managed cluster name>  # export MANAGED_CLUSTER_NAME=cluster1

# Deploy the controller
kubectl apply -f ${GIT_PATH}/operator.yaml -n ${MANAGED_NAMESPACE}
kubectl set env deployment/${COMPONENT} -n ${MANAGED_NAMESPACE} --containers=${COMPONENT} WATCH_NAMESPACE=${MANAGED_CLUSTER_NAME}

  2. Ensure the pod is running on the managed cluster with the following command:

    $ kubectl get pods -n ${MANAGED_NAMESPACE}
NAME                                               READY   STATUS    RESTARTS   AGE
config-policy-controller-7f8fb64d8c-pmfx4          1/1     Running   0          44s

Sample configuration policy

After a successful deployment, test the policy framework and configuration policy controller with a sample policy. You can use a policy that includes a Placement mapping or if you installed Application management’s PlacementRule support you can use either placement implementation. Perform the steps in the Placement API or the Placement Rule API section based on which placement API you desire to use.

For more information on how to use a ConfigurationPolicy, read the Policy API concept section.

Placement API

  1. Run the following command to create a policy on the hub that uses Placement:

    # Configure kubectl to point to the hub cluster
kubectl config use-context ${CTX_HUB_CLUSTER}

# Apply the example policy and placement
kubectl apply -n default -f https://raw.githubusercontent.com/open-cluster-management-io/policy-collection/main/community/CM-Configuration-Management/policy-pod-placement.yaml

  2. Update the Placement to distribute the policy to the managed cluster with the following command (this clusterSelector will deploy the policy to all managed clusters):

    kubectl patch -n default placement.cluster.open-cluster-management.io/placement-policy-pod --type=merge -p "{\"spec\":{\"predicates\":[{\"requiredClusterSelector\":{\"labelSelector\":{\"matchExpressions\":[]}}}]}}"

  3. Make sure the default namespace has a ManagedClusterSetBinding for a ManagedClusterSet with at least one managed cluster resource in the ManagedClusterSet. See Bind ManagedClusterSet to a namespace for more information on this.

  4. To confirm that the managed cluster is selected by the Placement, run the following command:

    $ kubectl get -n default placementdecision.cluster.open-cluster-management.io/placement-policy-pod-decision-1 -o yaml
...
status:
  decisions:
  - clusterName: <managed cluster name>
    reason: ""
...

Placement Rule API

NOTE: Skip this section if you applied the Placement API policy manifests.

  1. Run the following command to create a policy on the hub that uses PlacementRule:

    # Configure kubectl to point to the hub cluster
kubectl config use-context ${CTX_HUB_CLUSTER}

# Apply the example policy and placement rule
kubectl apply -n default -f https://raw.githubusercontent.com/open-cluster-management-io/policy-collection/main/stable/CM-Configuration-Management/policy-pod.yaml

  2. Update the PlacementRule to distribute the policy to the managed cluster with the following command (this clusterSelector will deploy the policy to all managed clusters):

    $ kubectl patch -n default placementrule.apps.open-cluster-management.io/placement-policy-pod --type=merge -p "{\"spec\":{\"clusterSelector\":{\"matchExpressions\":[]}}}"
placementrule.apps.open-cluster-management.io/placement-policy-pod patched

  3. To confirm that the managed cluster is selected by the PlacementRule, run the following command:

    $ kubectl get -n default placementrule.apps.open-cluster-management.io/placement-policy-pod -o yaml
...
status:
  decisions:
  - clusterName: ${MANAGED_CLUSTER_NAME}
    clusterNamespace: ${MANAGED_CLUSTER_NAME}
...

Final steps to apply the policy

Perform the following steps to continue working with the policy to test the policy framework now that a placement method has been selected between Placement or PlacementRule.

  1. Enforce the policy to make the configuration policy automatically correct any misconfigurations on the managed cluster:

    $ kubectl patch -n default policy.policy.open-cluster-management.io/policy-pod --type=merge -p "{\"spec\":{\"remediationAction\": \"enforce\"}}"
policy.policy.open-cluster-management.io/policy-pod patched

  2. After a few seconds, your policy is propagated to the managed cluster. To confirm, run the following command:

    $ kubectl config use-context ${CTX_MANAGED_CLUSTER}
$ kubectl get policy -A
NAMESPACE   NAME                 REMEDIATION ACTION   COMPLIANCE STATE   AGE
cluster1    default.policy-pod   enforce              Compliant          4m32s

  3. The missing pod is created by the policy on the managed cluster. To confirm, run the following command on the managed cluster:

    $ kubectl get pod -n default
NAME               READY   STATUS    RESTARTS   AGE
sample-nginx-pod   1/1     Running   0          23s
Last modified September 20, 2024: Refactor using docsy. (#429) (3f36d75)