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Direct Connection

If the kube-apiserver address of the member cluster is accessible on any node of the host cluster, you can adopt Direction Connection. This method is applicable when the kube-apiserver address of the member cluster can be exposed or host cluster and member cluster are in the same private network or subnet.

To use the multi-cluster feature using direct connection, you must have at least two clusters serving as the host cluster and the member cluster respectively. A cluster can be defined as the host cluster or the member cluster either before or after you install KubeSphere. For more information about installing KubeSphere, refer to Installing on Linux and Installing on Kubernetes.

Video Demonstration

Prepare a Host Cluster

A host cluster provides you with the central control plane and you can only define one host cluster.

If you already have a standalone KubeSphere cluster installed, you can set the value of clusterRole to host by editing the cluster configuration.

Option A - Use the web console:

Use the admin account to log in to the console and go to CRDs on the Cluster Management page. Enter the keyword ClusterConfiguration and go to its detail page. Edit the YAML of ks-installer, which is similar to Enable Pluggable Components.

Option B - Use Kubectl:

kubectl edit cc ks-installer -n kubesphere-system

In the YAML file of ks-installer, navigate to multicluster, set the value of clusterRole to host, then click OK (if you use the web console) to make it effective:

multicluster:
  clusterRole: host

To set the host cluster name, add a field hostClusterName under multicluster.clusterRole in the YAML file of ks-installer:

multicluster:
  clusterRole: host
  hostClusterName: <Host cluster name>

Note

It is recommended that you set the host cluster name while you are preparing your host cluster. When your host cluster is set up and running with resources deployed, it is not recommended that you set the host cluster name.
The host cluster name can contain only lowercase letters, numbers, hyphens (-), or periods (.), and must start and end with a lowercase letter or number.

You need to wait for a while so that the change can take effect.

You can define a host cluster before you install KubeSphere either on Linux or on an existing Kubernetes cluster. If you want to install KubeSphere on Linux, you use a config-sample.yaml file. If you want to install KubeSphere on an existing Kubernetes cluster, you use two YAML files, one of which is cluster-configuration.yaml.

To set a host cluster, change the value of clusterRole to host in config-sample.yaml or cluster-configuration.yaml accordingly before you install KubeSphere.

multicluster:
  clusterRole: host

To set the host cluster name, add a field hostClusterName under multicluster.clusterRole in config-sample.yaml or cluster-configuration.yaml:

multicluster:
  clusterRole: host
  hostClusterName: <Host cluster name>

Note

The host cluster name can contain only lowercase letters, numbers, hyphens (-), or periods (.), and must start and end with a lowercase letter or number.

Info

If you install KubeSphere on a single-node cluster (All-in-One), you do not need to create a config-sample.yaml file. In this case, you can set a host cluster after KubeSphere is installed.

You can use kubectl to retrieve the installation logs to verify the status by running the following command. Wait for a while, and you will be able to see the successful log return if the host cluster is ready.

kubectl logs -n kubesphere-system $(kubectl get pod -n kubesphere-system -l 'app in (ks-install, ks-installer)' -o jsonpath='{.items[0].metadata.name}') -f

Prepare a Member Cluster

In order to manage the member cluster from the host cluster, you need to make jwtSecret the same between them. Therefore, get it first by excuting the following command on the host cluster.

kubectl -n kubesphere-system get cm kubesphere-config -o yaml | grep -v "apiVersion" | grep jwtSecret

The output may look like this:

jwtSecret: "gfIwilcc0WjNGKJ5DLeksf2JKfcLgTZU"

If you already have a standalone KubeSphere cluster installed, you can set the value of clusterRole to member by editing the cluster configuration.

Option A - Use the web console:

Use the admin account to log in to the console and go to CRDs on the Cluster Management page. Enter the keyword ClusterConfiguration and go to its detail page. Edit the YAML of ks-installer, which is similar to Enable Pluggable Components.

Option B - Use Kubectl:

kubectl edit cc ks-installer -n kubesphere-system

In the YAML file of ks-installer, enter the corresponding jwtSecret shown above:

authentication:
  jwtSecret: gfIwilcc0WjNGKJ5DLeksf2JKfcLgTZU

Scroll down and set the value of clusterRole to member, then click OK (if you use the web console) to make it effective:

multicluster:
  clusterRole: member

You need to wait for a while so that the change can take effect.

You can define a member cluster before you install KubeSphere either on Linux or on an existing Kubernetes cluster. If you want to install KubeSphere on Linux, you use a config-sample.yaml file. If you want to install KubeSphere on an existing Kubernetes cluster, you use two YAML files, one of which is cluster-configuration.yaml. To set a member cluster, enter the value of jwtSecret shown above and change the value of clusterRole to member in config-sample.yaml or cluster-configuration.yaml accordingly before you install KubeSphere.

authentication:
  jwtSecret: gfIwilcc0WjNGKJ5DLeksf2JKfcLgTZU

multicluster:
  clusterRole: member

Note

If you install KubeSphere on a single-node cluster (All-in-One), you do not need to create a config-sample.yaml file. In this case, you can set a member cluster after KubeSphere is installed.

kubectl logs -n kubesphere-system $(kubectl get pod -n kubesphere-system -l 'app in (ks-install, ks-installer)' -o jsonpath='{.items[0].metadata.name}') -f

Import a Member Cluster

Log in to the KubeSphere console as admin and click Add Cluster on the Cluster Management page.
Enter the basic information of the cluster to be imported on the Import Cluster page. You can also click Edit Mode in the upper-right corner to view and edit the basic information in YAML format. After you finish editing, click Next.
In Connection Method, select Direct connection, and copy the kubeconfig of the member cluster and paste it into the box. You can also click Edit Mode in the upper-right corner to edit the kubeconfig of the member cluster in YAML format.

Note

Make sure the server address in KubeConfig is accessible on any node of the host cluster.
Click Create and wait for cluster initialization to finish.

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