Attach an existing GKE cluster in DKP

You can attach existing Kubernetes clusters to the Management Cluster. After attaching the cluster, you can use the UI to examine and manage this cluster. The following procedure shows how to attach an existing standard GKE cluster.

Before you begin

This procedure requires the following items and configurations:

This procedure assumes you have an existing and spun up GKE cluster with administrator privileges.

Attach GKE Clusters

Ensure you have access to your GKE clusters

  1. Ensure you are connected to your GKE clusters. Enter the following commands for each of your clusters:

    kubectl config get-contexts
    kubectl config use-context <context for first gcloud cluster>
    CODE
  2. Confirm kubectl can access the GKE cluster.

    kubectl get nodes
    CODE

Configure a kubeconfig file

  1. Create the necessary service account:

    kubectl -n kube-system create serviceaccount kommander-cluster-admin
    CODE
  2. Create a token secret for the serviceaccount:

    kubectl -n kube-system create  -f - <<EOF
    apiVersion: v1
    kind: Secret
    metadata:
      name: kommander-cluster-admin-sa-token
      annotations:
        kubernetes.io/service-account.name: kommander-cluster-admin
    type: kubernetes.io/service-account-token
    EOF
    CODE
  3. Verify that the serviceaccount token is ready by running this command:

    kubectl -n kube-system get secret kommander-cluster-admin-sa-token -oyaml
    CODE

    Verify that the data.token field is populated. The output should be similar to this:

    apiVersion: v1
    data:
      ca.crt: LS0tLS1CRUdJTiBDR...
      namespace: ZGVmYXVsdA==
      token: ZXlKaGJHY2lPaUpTVX...
    kind: Secret
    metadata:
      annotations:
        kubernetes.io/service-account.name: kommander-cluster-admin
        kubernetes.io/service-account.uid: b62bc32e-b502-4654-921d-94a742e273a8
      creationTimestamp: "2022-08-19T13:36:42Z"
      name: kommander-cluster-admin-sa-token
      namespace: default
      resourceVersion: "8554"
      uid: 72c2a4f0-636d-4a70-9f1c-55a75f15e520
    type: kubernetes.io/service-account-token
    NONE
  4. Configure the new service account for cluster-admin permissions:

    cat << EOF | kubectl apply -f -
    apiVersion: rbac.authorization.k8s.io/v1
    kind: ClusterRoleBinding
    metadata:
      name: kommander-cluster-admin
    roleRef:
      apiGroup: rbac.authorization.k8s.io
      kind: ClusterRole
      name: cluster-admin
    subjects:
    - kind: ServiceAccount
      name: kommander-cluster-admin
      namespace: kube-system
    EOF
    NONE
  5. Set up the following environment variables with the access data that is needed for producing a new kubeconfig file:

    export USER_TOKEN_VALUE=$(kubectl -n kube-system get secret/kommander-cluster-admin-sa-token -o=go-template='{{.data.token}}' | base64 --decode)
    export CURRENT_CONTEXT=$(kubectl config current-context)
    export CURRENT_CLUSTER=$(kubectl config view --raw -o=go-template='{{range .contexts}}{{if eq .name "'''${CURRENT_CONTEXT}'''"}}{{ index .context "cluster" }}{{end}}{{end}}')
    export CLUSTER_CA=$(kubectl config view --raw -o=go-template='{{range .clusters}}{{if eq .name "'''${CURRENT_CLUSTER}'''"}}"{{with index .cluster "certificate-authority-data" }}{{.}}{{end}}"{{ end }}{{ end }}')
    export CLUSTER_SERVER=$(kubectl config view --raw -o=go-template='{{range .clusters}}{{if eq .name "'''${CURRENT_CLUSTER}'''"}}{{ .cluster.server }}{{end}}{{ end }}')
    NONE
  6. Confirm these variables have been set correctly:

    export -p USER_TOKEN_VALUE CURRENT_CONTEXT CURRENT_CLUSTER CLUSTER_CA CLUSTER_SERVER
    NONE
  7. Generate a kubeconfig file that uses the environment variable values from the previous step:

    cat << EOF > kommander-cluster-admin-config
    apiVersion: v1
    kind: Config
    current-context: ${CURRENT_CONTEXT}
    contexts:
    - name: ${CURRENT_CONTEXT}
      context:
        cluster: ${CURRENT_CONTEXT}
        user: kommander-cluster-admin
        namespace: kube-system
    clusters:
    - name: ${CURRENT_CONTEXT}
      cluster:
        certificate-authority-data: ${CLUSTER_CA}
        server: ${CLUSTER_SERVER}
    users:
    - name: kommander-cluster-admin
      user:
        token: ${USER_TOKEN_VALUE}
    EOF
    NONE
  8. This process produces a file in your current working directory called kommander-cluster-admin-config. The contents of this file are used in Kommander to attach the cluster.
    Before importing this configuration, verify the kubeconfig file can access the cluster:

    kubectl --kubeconfig $(pwd)/kommander-cluster-admin-config get all --all-namespaces
    NONE

Attach the cluster

Now that you have a kubeconfig file, go to the DKP UI and follow these steps:

  1. Select your target workspace from the top menu bar.

  2. Select Add Cluster in the Actions dropdown menu from the Dashboard page, located at the top-right.

  3. Select Attach Cluster.

  4. Select the No additional networking restrictions card.
    Alternatively, if you must use network restrictions, stop following the steps below, and see the instructions on the page Attach a cluster WITH network restrictions.

  5. Upload the kubeconfig file you created in the previous section (or copy its contents) into the Cluster Configuration section.

  6. The Cluster Name field automatically populates with the name of the cluster in the kubeconfig. You can edit this field with the name you want for your cluster.

  7. Add labels to classify your cluster as needed.

  8. Select Create to attach your cluster.

If a cluster has limited resources to deploy all the federated platform services, it will fail to stay attached in the DKP UI. If this happens, ensure your system has sufficient resources for all pods.

Related information

For information on related topics or procedures, refer to the following: