.kube config

Internal

• Kubernetes Configuration
• kubectl
• EKS .kube/config

Overview

$HOME/.kube/config is kubectl configuration file. It contains definitions for clusters, users and contexts. The content of the file can be displayed with:

kubectl config view

Clusters

The "clusters" section of $HOME/.kube/config contains the definition of one or more clusters. Each cluster definition has a name, certificate info and the API server's endpoint.

clusters:
- cluster:
    certificate-authority-data: LS0tLS1...tLQo=
    server: https://kubernetes.docker.internal:6443
  name: docker-desktop

Cluster Operations

List all Clusters

kubectl config get-clusters

Users

The "users" section of $HOME/.kube/config contains definitions of users that might have different levels of permissions for each cluster. Each user definition has a friendly name, a username and a set of credentials. The credentials are the certificate the user needs to connect to the API server. In OpenShift's case, the original content of ~/.kube/config for the Unix root account of the master server is created by copying it from /etc/openshift/master/admin.kubeconfig.

users:
- name: docker-desktop
  user:
    client-certificate-data: LS0tL...LS0K
    client-key-data: LS0tL...tLQo=
- name: test-admin
  user:
    password: M1...0K
    username: admin

User Operations

Adding a User

Simply add the section to $HOME/.kube/config.

Contexts

Contexts bring together clusters and users under a friendly name. The contexts are declared in the "contexts" section of $HOME/.kube/config.

current-context: docker-desktop
contexts:
- context:
    cluster: docker-desktop
    user: docker-desktop
  name: docker-desktop

Current Context

At any moment, there's a context that is "current" - meaning that all kubectl invocations are directed to the cluster designated by the current context, with the identity set as part of the current context.

Context Operations

List All Contexts

All contexts can be obtained with:

kubectl config get-contexts

Show Current Context

The current context can be viewed with:

kubectl config current-context

and can be changed with:

kubectl config use-context new-context-name

Set a Current Context

 kubectl config use-context <context-name>

Delete a Context

kubectl config delete-context <context-name>

Rename a Context

TODO

Creating a Client Configuration from Scratch

This procedure is useful if we install kubectl only on a remote client machine and we need it to configure it to connect to a Kubernetes cluster.

• Download kubectl and install it as described here: kubectl Installation.
• Create a ~/.kube directory.
• Create a ~/.kube/config file with the following content:

apiVersion: v1
kind: Config
clusters:
- name: kubernetes-kubespray
  cluster:
    certificate-authority-data: LS0tL...LQo=
    server: https://10.10.2.146:6443
users:
- name: kubernetes-kubespray-admin
  user:
    client-certificate-data: LS0t...tLQo=
    client-key-data: LS0tLS...S0tLQo=
contexts:
- name: kubernetes-kubespray
  context:
    cluster: kubernetes-kubespray
    user: kubernetes-kubespray-admin
current-context: kubernetes-kubespray
preferences: {}

The cluster certificate-authority-data is obtained as follows.

The user client-certificate-data is obtained as follows.

The user client-key-data is obtained as follows.

KUBECONFIG and Multiple Configuration Files

kubectl first look at the the KUBECONFIG environment variable to determine where its configuration is. As such, different terminals (environments) can set the value of the environment variable differently and access different sets of Kubernetes contexts:

export KUBECONFIG=~/some-kubeconfig

This way you can set up different terminals "dedicated" to different clusters.