Attach an Existing Kubernetes Cluster

Attach an existing Kubernetes cluster using kubeconfig

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 Configuration Requirements to ensure the attached cluster has sufficient resources. For more information on platform applications and customizing them, see Workspace 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.

Create a kubeconfig file for your EKS cluster

If you already have a kubeconfig file, SKIP this section.

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

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
```

Finalize attaching your cluster from the UI

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.

From the top menu bar, select your target workspace.
On the Dashboard page, select the Add Cluster option in the Actions dropdown menu 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 is in the kubeconfig. You can edit this field with the name you want for your cluster.
The Context select list is populated from the kubeconfig. Select the desired context with admin privileges from the Context select list.
Add labels to classify your cluster as needed.
Select Create 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 Applications.