Quick Start

After walking through our Quick Start guide you will:

  • Install and run Open Cluster Management(OCM)‘s command-line tool clusteradm.
  • Bootstrap an OCM’s hub cluster as the multi-cluster control plane.
  • Register another cluster as OCM’s managed cluster.
  • Approving the managed cluster to be controlled by hub cluster.

Contents

Prerequisites

  • The hub cluster should be v1.19+. (To run on hub cluster version between [v1.16, v1.18], please manually enable feature gate “V1beta1CSRAPICompatibility”).
  • The managed clusters should be v1.11+.

You can always set up a local KinD environment on your workstation easily by following these instructions after meeting the following additional prerequisites:

  • KinD greater than v0.9.0+, or the latest version is preferred.

Environment

In this section, we will be warming up by preparing your terminal environment before actually installing OCM to your clusters. You can skip the KinD setup below if you’d like to install OCM into your existing clusters.

Setup a local KinD environment

To create two local running clusters on your workstation, run:

kind create cluster --name hub
kind create cluster --name cluster1

Remember that the cluster named “hub” will be the multi-cluster control plane of your OCM environment, and “cluster1” is supposed to be the managed cluster controlled by “hub”.

Prepare terminal environment

Before actually installing the OCM components into your clusters, export the following environment variables in your terminal before running our command-line tool clusteradm so that it can correctly discriminate the hub cluster and managed cluster:

# 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

Bootstrap via clusteradm CLI tool

In this section, we will be bootstrapping an OCM environment with the help of OCM’s native clusteradm command-line tool.

Install clusteradm CLI tool

It’s recommended to run the following command to download and install the latest release of the clusteradm command-line tool:

curl -L https://raw.githubusercontent.com/open-cluster-management-io/clusteradm/main/install.sh | bash

You can also install the latest development version (main branch) by running:

# Installing clusteradm to $GOPATH/bin/
GO111MODULE=off go get -u open-cluster-management.io/clusteradm/...

Overview of the registration process

The following video shows how to bootstrap a hub cluster control plane and register another cluster with the hub.

Cluster proxy architecture

To try out the cluster registration, let’s walk through the following steps:

Deploy a cluster manager on your hub cluster

  1. Bootstrap the Open Cluster Management control plane (i.e. the hub cluster):

    # By default, it installs the latest release of the OCM components.
    # Use e.g. "--bundle-version=latest" to install latest development builds.
    # NOTE: For hub cluster version between v1.16 to v1.19 use the parameter: --use-bootstrap-token
    clusteradm init --wait --context ${CTX_HUB_CLUSTER}
    

    The clusteradm init command installs the registration-operator on the hub cluster, which is responsible for consistently installing and upgrading a few core components for the OCM environment.

    After the init command completes, a generated command is output on the console to register your managed clusters. An example of the generated command is shown below.

    # NOTE: For KinD clusters use the parameter: --force-internal-endpoint-lookup
    clusteradm join \
         --hub-token <your token data> \
         --hub-apiserver <your hub kube-apiserver endpoint> \
         --wait \
         --cluster-name <cluster_name>
    

    It’s recommended to save the command somewhere secure for future use. If it’s lost, you can use clusteradm get token to get the generated command again.

  2. Then you can check out the running instances of registration operator by:

    kubectl -n open-cluster-management get pod --context ${CTX_HUB_CLUSTER}
    NAME                               READY   STATUS    RESTARTS   AGE
    cluster-manager-695d945d4d-5dn8k   1/1     Running   0          19d
    

    Additionally, to check out the instances of OCM’s hub control plane, run the following command:

    kubectl -n open-cluster-management-hub get pod --context ${CTX_HUB_CLUSTER}
    NAME                               READY   STATUS    RESTARTS   AGE
    cluster-manager-placement-controller-857f8f7654-x7sfz      1/1     Running   0          19d
    cluster-manager-registration-controller-85b6bd784f-jbg8s   1/1     Running   0          19d
    cluster-manager-registration-webhook-59c9b89499-n7m2x      1/1     Running   0          19d
    cluster-manager-work-webhook-59cf7dc855-shq5p              1/1     Running   0          19d
    ...
    

    The overall installation information is visible on the clustermanager custom resource:

    kubectl get clustermanager cluster-manager -o yaml --context ${CTX_HUB_CLUSTER}
    

Deploy a klusterlet agent on your managed cluster

Once all the pods of the hub components are running, your hub cluster is all set. Let’s move on to register your managed cluster into OCM.

  1. Run the previously generated command from init. Note that you’re supposed to explicitly pass the --context option if your managed cluster is created by KinD because its kubeconfig is persisted in the same kubeconfig file of the hub cluster.

    # NOTE: Switch kubeconfig to the managed cluster.
    # NOTE: For KinD clusters use the parameter: --force-internal-endpoint-lookup
    clusteradm join \
         --context ${CTX_MANAGED_CLUSTER} \
         --hub-token <your token data> \
         --hub-apiserver <your hub cluster endpoint> \
         --wait \
         --cluster-name "cluster1"    # Or other arbitrary unique name
    
  2. Verify the installation of the klusterlet registration agent in your managed clusters by running:

    kubectl -n open-cluster-management-agent get pod --context ${CTX_MANAGED_CLUSTER}
    NAME                                             READY   STATUS    RESTARTS   AGE
    klusterlet-registration-agent-598fd79988-jxx7n   1/1     Running   0          19d
    

    Similar to clustermanager, the overall installation information is described by another custom resource called klusterlet, which is only installed on the managed clusters. You may view this information by running:

    kubectl get klusterlet klusterlet -o yaml --context ${CTX_MANAGED_CLUSTER}
    

Accept the join request and verify

After the OCM agent is running on your managed cluster, it will be sending a “handshake” to your hub cluster and waiting for an approval from the hub cluster admin. In this section, we will walk through accepting the registration requests from the prespective of an OCM’s hub admin.

  1. Wait for the creation of the CSR object which will be created by your managed clusters’ OCM agents on the hub cluster:

    kubectl get csr -w --context ${CTX_HUB_CLUSTER} | grep cluster1  # or the previously chosen cluster name
    

    An example of a pending CSR request is shown below:

    cluster1-tqcjj   33s   kubernetes.io/kube-apiserver-client   system:serviceaccount:open-cluster-management:cluster-bootstrap   Pending
    
  2. Accept the join request using the clusteradm tool:

    clusteradm accept --clusters cluster1 --context ${CTX_HUB_CLUSTER}
    

    After running the accept command, the CSR from your managed cluster named “cluster1” will be approved. Additionally, it will instruct the OCM hub control plane to setup related objects (such as a namespace named “cluster1” in the hub cluster) and RBAC permissions automatically.

  3. Verify the installation of the OCM agents on your managed cluster by running:

    kubectl -n open-cluster-management-agent get pod --context ${CTX_MANAGED_CLUSTER}
    NAME                                             READY   STATUS    RESTARTS   AGE
    klusterlet-registration-agent-598fd79988-jxx7n   1/1     Running   0          19d
    klusterlet-work-agent-7d47f4b5c5-dnkqw           1/1     Running   0          19d
    
  4. Verify that the cluster1 ManagedCluster object was created successfully by running:

    kubectl get managedcluster --context ${CTX_HUB_CLUSTER}
    

    Then you should get a result that resembles the following:

    NAME       HUB ACCEPTED   MANAGED CLUSTER URLS      JOINED   AVAILABLE   AGE
    cluster1   true           <your endpoint>           True     True        5m23s
    

Bootstrap via Operatorhub.io

Install and create a Cluster manager on your hub cluster.

Install and create a Klusterlet agent on your managed cluster.

What is next

Now you have the OCM control plane with at least one managed cluster connected! Let’s start your OCM journey.

To understand more about OCM API details, see Core components.