How to Switch Kubernetes Contexts When Managing Multiple Clusters

Answer: To switch between multiple Kubernetes clusters, you’ll need a Kubernetes configuration file (e.g., ~/.kube/config) that contains access credentials for each cluster. This configuration file can hold multiple Kubernetes context configurations, combining access details from several kubeconfig files.

For more information on setting up configuration files, refer to the official Kubernetes documentation.

What You Need to Do

Check your Client and Server Versions

Begin by verifying the version of your Kubernetes client (kubectl) and server (e.g., kubeadm). This ensures compatibility between the versions.

$ kubectl version --client

The output of this command should look something like:

Client Version: v1.27.3
Kustomize Version: v5.0.1
Server Version: v1.30.0

Warning: The difference between the client and server versions should not exceed the supported minor version skew of ±1.

In this example, the client version (1.27) and server version (1.30) exceed the supported version skew. Therefore, updating the kubectl client is necessary. Find more information on this in the official documentation.

Make Sure You Have Access to Multiple Clusters

You’ll need access to two or more Kubernetes clusters to benefit from switching contexts.

Verify the KUBECONFIG Environment Variable

Ensure that your KUBECONFIG environment variable points to all relevant configuration files, like so:

$ env | grep -i kub
KUBECONFIG=/home/user/.kube/config-prod:/home/user/.kube/config-dev

Alternatively, you can use the kubectl command to confirm that all configurations are loaded:

$ kubectl config view
apiVersion: v1
clusters:
- cluster:
    certificate-authority-data: DATA+OMITTED
    server: https://my-dev-cluster
  name: dev-cluster
- cluster:
    certificate-authority-data: DATA+OMITTED
    server: https://my-prod-cluster
  name: prod-cluster
contexts:
- context:
    cluster: dev-cluster
    namespace: default
    user: developer
  name: development
- context:
    cluster: prod-cluster
    user: producer
  name: production
current-context: ""
kind: Config
preferences: {}
users:
- name: developer
  user:
    client-certificate-data: DATA+OMITTED
    client-key-data: DATA+OMITTED
- name: producer
  user:
    client-certificate-data: DATA+OMITTED
    client-key-data: DATA+OMITTED

Since the KUBECONFIG environment variable is set, kubectl recognizes and displays both configurations.

Merge Configuration Files into a Single File

To simplify switching contexts, merge multiple configuration files into one. The kubectl command makes this easy:

$ kubectl config view --merge --flatten > ~/.kube/config-merged

This command does the following:

• --merge: Combines the configurations from multiple files.
• --flatten: Produces a standalone, portable configuration file.

Once the merged KUBECONFIG is created, you can easily switch contexts using the kubectl client, or with tools like kubectx and k9s.

Note: If you need to create a configuration file from scratch, this can also be done with the kubectl client. Detailed steps are available in the Kubernetes documentation.