Attach an Existing Kubernetes Cluster

Attach Kubernetes Cluster

You can attach an existing cluster directly to Kommander. At the time of attachment, certain namespaces are created on the cluster, and workspace platform applications are deployed automatically into the newly-created namespaces.

Review the workspace platform application resource requirements to ensure the attached cluster has sufficient resources. For more information on platform applications and customizing them, see workspace platform applications.

If the cluster you want to attach was created using Amazon EKS or Google GKE, create a service account as described below. If you are attaching an Amazon EKS cluster to Kommander, detailed instructions are available.

Prerequisites

This step is optional, if you already have a kubeconfig file. You can go directly to Attaching a cluster.

You must create a separate service account when attaching existing Amazon EKS or Google GKE Kubernetes clusters. This is necessary because the kubeconfig files generated from those clusters are not usable out-of-the-box by Kommander. The kubeconfig files call CLI commands, such as aws or gcloud, and use locally-obtained authentication tokens. Having a separate service account also allows you to keep access to the cluster specific and isolated to Kommander.

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

1. Create the necessary service account:

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

2. 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
   

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

   export USER_TOKEN_NAME=$(kubectl -n kube-system get serviceaccount kommander-cluster-admin -o=jsonpath='{.secrets[0].name}')
   export USER_TOKEN_VALUE=$(kubectl -n kube-system get secret/${USER_TOKEN_NAME} -o=go-template='{{.data.token}}' | base64 --decode)
   export CURRENT_CONTEXT=$(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 }}')
   

4. 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
   

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, you can verify that it is functional by running the following command:

kubectl --kubeconfig $(pwd)/kommander-cluster-admin-config get all --all-namespaces

Attaching a Cluster

Using the Add Cluster option, you can attach an existing Kubernetes or Konvoy cluster directly to Kommander. This enables you to access the multi-cluster management and monitoring benefits that Kommander provides, while keeping your existing cluster on its current provider and infrastructure.

1. From the top menu bar, select your target workspace.

2. On the Dashboard page, select the Add Cluster option in the Actions dropdown menu at the top right.

3. Select Attach Cluster.

4. Select the No additional networking restrictions card.

5. In the Cluster Configuration section, paste your kubeconfig file into the field, or select the Upload kubeconfig File button to specify the file.

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

7. The Context select list is populated from the kubeconfig. Select the desired context with admin privileges from the Context select list.

8. Add labels to classify your cluster as needed.

9. Select Submit to attach your cluster.

Platform applications extend the functionality of Kubernetes and provide ready-to-use logging and monitoring stacks by deploying platform applications when attaching a cluster to Kommander. For more information, refer to workspace platform applications.