To attach an existing cluster to Kommander, the Kommander management cluster must be able to reach the services and the
api-server of the target cluster.
For attaching existing clusters without networking restrictions, the requirements depend on which Kommander version you are using. Each version of Kommander supports a specific range of Kubernetes versions. You must ensure that the target cluster is running a compatible version.
For example, Kommander 2.2 supports Kubernetes versions between 1.21.0 and 1.22.x. Any cluster you want to attach using Kommander 2.2 must be running a Kubernetes version in that range.
Creating a default StorageClass
To deploy many of the services on the attached cluster, there must be a default
StorageClass configured. Run the following command on the cluster you want to attach:
kubectl get sc
The output should look similar to this. Note the
(default) after the name:
NAME PROVISIONER RECLAIMPOLICY VOLUMEBINDINGMODE ALLOWVOLUMEEXPANSION AGE ebs-sc (default) ebs.csi.aws.com Delete WaitForFirstConsumer false 41s
StorageClass is not set as default, add the following annotation to the
annotations: storageclass.kubernetes.io/is-default-class: "true"
Creating Projects and Workspaces
Before you attach clusters, you need to create one or more Workspaces, and we recommend that you also create Projects within your Workspaces. Workspaces give you a logical way to represent your teams and specific configurations. Projects let you define one or more clusters as a group to which Kommander pushes a common configuration. Grouping your existing clusters in Kommander projects and workspaces makes managing their platform services and resources easier and supports monitoring and logging.
Platform application requirements
In addition to the basic cluster requirements, the platform services you want Kommander to manage on those clusters will have an impact on the total cluster requirements. The specific combinations of platform applications will make a difference in the requirements for the cluster nodes and their resources (CPU, memory, and storage).
See this table of platform applications that Kommander provides by default.
Attaching existing AWS and EKS clusters
Attaching an existing, Amazon-provisioned cluster requires that the cluster be fully configured and running. The suggested default cluster configuration includes a control plane pool containing three (3) m5.xlarge nodes and a worker pool containing four (4) m5.2xlarge nodes.
Consider the additional resource requirements for running the platform services you want Kommander to manage, and ensure that your existing clusters comply.
To attach an existing EKS cluster, refer to the specific information in Attach Amazon EKS Cluster to Kommander.
Attach clusters with an existing cert-manager installation
If you are attaching clusters that already have cert-manager installed, the cert-manager
HelmRelease provided by Kommander will fail to deploy, due to the existing cert-manager installation. As long as the pre-existing cert-manager functions as expected, you can ignore this failure. It will have no impact on the operation of the cluster.