Attach GKE Cluster

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:

A fully configured and running GKE cluster with a supported Kubernetes version, and administrative privileges.
The current version of DKP Enterprise installed on your cluster.
Ensure you have installed kubectl in your Management cluster.

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

Ensure you are connected to your GKE clusters. Enter the following commands for each of your clusters:
BASH
```
kubectl config get-contexts
kubectl config use-context <context for first gcloud cluster>
```
Confirm kubectl can access the GKE cluster.
CODE
```
kubectl get nodes
```

Configure a kubeconfig file

To get started, ensure you have kubectl set up and configured with ClusterAdmin for the cluster you want to connect to Kommander.

Create the necessary service account:

CODE

kubectl -n kube-system create serviceaccount kommander-cluster-admin

Create a token secret for the serviceaccount:

CODE

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

For more information on Service Account Tokens, refer to this article in our blog.

Verify that the serviceaccount token is ready by running this command:

CODE

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

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

NONE

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

Configure the new service account for cluster-admin permissions:

NONE

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

Set up the following environment variables with the access data that is needed for producing a new kubeconfig file:

NONE

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 }}')

Confirm these variables have been set correctly:

NONE

export -p | grep -E 'USER_TOKEN_VALUE|CURRENT_CONTEXT|CURRENT_CLUSTER|CLUSTER_CA|CLUSTER_SERVER'

Generate a kubeconfig file that uses the environment variable values from the previous step:

NONE

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

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

Attach the Cluster

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

Select your target workspace from the top menu bar.
Select Add Cluster in the Actions dropdown menu from the Dashboard page, located at the top-right.
Select Attach Cluster.
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.
Upload the kubeconfig file you created in the previous section (or copy its contents) into the Cluster Configuration section.
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.
Add labels to classify your cluster as needed.
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: