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Accessing Kubernetes Clusters

Context and kubeconfig

kubectl allows a user to interact with and manage multiple Kubernetes clusters. To do this, it requires what is known as a context. A context consists of a combination of cluster, namespace and user. * cluster - A friendly name, server address, and certificate for the Kubernetes cluster. * namespace (optional) - The logical cluster or environment to use. If none is provided, it will use the default default namespace. * user - The credentials used to connect to the cluster. This can be a combination of client certificate and key, username/password, or token.

These contexts are stored in a local yaml based config file referred to as the kubeconfig. For *nix based systems, the kubeconfig is stored in $HOME/.kube/config for Windows, it can be found in %USERPROFILE%/.kube/config

This config is viewable without having to view the file directly.

Command 

$ kubectl config view

Example 

❯ kubectl config view
apiVersion: v1
clusters:
- cluster:
    certificate-authority-data: DATA+OMITTED
    server: https://127.0.0.1:46347
  name: kind-kind
contexts:
- context:
    cluster: kind-kind
    user: kind-kind
  name: kind-kind
current-context: kind-kind
kind: Config
preferences: {}
users:
- name: kind-kind
  user:
    client-certificate-data: REDACTED
    client-key-data: REDACTED

kubectl config

Managing all aspects of contexts is done via the kubectl config command. Some examples include: * See the active context with kubectl config current-context. * Get a list of available contexts with kubectl config get-contexts. * Switch to using another context with the kubectl config use-context <context-name> command. * Add a new context with kubectl config set-context <context name> --cluster=<cluster name> --user=<user> --namespace=<namespace>.

There can be quite a few specifics involved when adding a context, for the available options, please see the Configuring Multiple Clusters Kubernetes documentation.

Exercise: Using Contexts

Objective: Create a new context called kind-dev and switch to it.

  1. View the current contexts. 

    $ kubectl config get-contexts

  2. Create a new context called kind-dev within the kind-kind cluster with the dev namespace, as the kind-kind user. 

    $ kubectl config set-context kind-dev --cluster=kind-kind --user=kind-kind --namespace=dev

  3. View the newly added context. 

    kubectl config get-contexts

  4. Switch to the kind-dev context using use-context. 

    $ kubectl config use-context kind-dev

  5. View the current active context. 

    $ kubectl config current-context

Summary: Understanding and being able to switch between contexts is a base fundamental skill required by every Kubernetes user. As more clusters and namespaces are added, this can become unwieldy. Installing a helper application such as kubectx can be quite helpful. Kubectx allows a user to quickly switch between contexts and namespaces without having to use the full kubectl config use-context command.