Having a managed cluster (edge) join the management hub

Table of contents

1. Allow ACM to deploy the managed cluster application to a subset of clusters
2. Deploy a managed cluster
3. Managed cluster setup using the ACM UI
4. Managed cluster setup using cm tool
5. Managed cluster setup using clusteradm tool
6. Managed cluster is joined
   1. Designate the new cluster as a managed cluster site
   2. You’re done

Allow ACM to deploy the managed cluster application to a subset of clusters

By default the clusterGroup applications are deployed on all clusters that ACM knows about. In you value-hub.yaml file add a managedClusterCgroup for each cluster or group of clusters that you want to manage was one.

  managedClusterGroups:
  - name: region-one
    helmOverrides:
    - name: clusterGroup.isHubCluster
      value: false
    clusterSelector:
      matchLabels:
        clusterGroup: region-one

The above yaml segment will deploy the clusterGroup applications on managed clusters with the label clusterGroup=region-one. Specific subscriptions and Operators, applications and projects for that clusterGroup are then managed in a value-region-one.yaml file. E.g.

  namespaces:
    - multicloud-gitops-region-one
    - ansible-automation-platform

  subscriptions:
    - name: ansible-automation-platform-operator
      namespace: ansible-automation-platform
      channel: stable-2.1
      csv: aap-operator.v2.1.0-0.1639138915


  projects:
    - ansible-automation-platform

  applications:
    - name: ansible
      project: ansible-automation-platform
      path: region/aap

Remember to commit the changes and push to GitHub so that GitOps can see your changes and apply them.

Deploy a managed cluster

Rather than provide instructions on creating a managed cluster it is assumed that an OpenShift cluster has already been created. Use the openshift-install program provided at cloud.redhat.com

There are a three ways to join the managed cluster to the management hub.

• Using the ACM user interface
• Using the cm tool
• Using the clusteradm tool

Managed cluster setup using the ACM UI

1. From the management hub openshift console select ACM from the top right

1. Select the “Import cluster” option beside the highleded Create Cluster button.

1. On the “Import an existing cluster” page, enter the cluster name and choose Kubeconfig as the “import mode”. Add the tag clusterGroup=region-one. Press import. Done.

Using this menthod, you are done. Skip to the section Managed cluster is joined but ignore the part about adding the site tag.

Managed cluster setup using cm tool

1. Install the cm (cluster management) CLI tool. See details here

2. Obtain the KUBECONFIG file from the managed-cluster cluster.

3. On the command line login into the management hub cluster (use oc login or export the KUBECONFIG).

4. Run the following command:

   cm attach cluster --cluster <cluster-name> --cluster-kubeconfig <path-to-KUBECONFIG>
   

Skip to the section Managed cluster is joined

Managed cluster setup using clusteradm tool

You can also use clusteradm to join a cluster. The folloing instructions explain what needs to be done. clusteradm is still in testing.

1. To deploy a edge cluster you will need to get the management hub cluster’s token. You will need to install clusteradm. On the existing management hub cluster:

   clusteradm get token

2. When you run the clusteradm command above it replies with the token and also shows you the command to use on the managed cluster. So first you must login to the managed cluster

   oc login or

   export KUBECONFIG=~/my-ocp-env/managed-cluster

3. Then request to that the managed cluster join the management hub

   clusteradm join --hub-token <token from clusteradm get token command > <managed cluster name>

4. Back on the hub cluster accept the join reguest

   clusteradm accept --clusters <managed-cluster-name>

Skip to the section Managed cluster is joined

Managed cluster is joined

Designate the new cluster as a managed cluster site

Now that ACM is no longer deploying the managed cluster applications everywhere, we need to explicitly indicate that the new cluster has the managed cluster role. If you haven’t tagged the cluster as clusterGroup=region-one then we can that here.

We do this by adding the label referenced in the managedSite’s clusterSelector.

1. Find the new cluster

   oc get region-one.cluster.open-cluster-management.io

2. Apply the label

   oc label region-one.cluster.open-cluster-management.io/YOURCLUSTER site=managed-cluster

You’re done

That’s it! Go to your managed cluster (edge) OpenShift console and check for the open-cluster-management-agent pod being launched. Be patient, it will take a while for the ACM agent and agent-addons to launch. After that, the operator OpenShifdt GitOps will run. When it’s finished coming up launch the OpenShift GitOps (ArgoCD) console from the top right of the OpenShift console.