kubectl config

Lens

https://github.com/MuhammedKalkan/OpenLens by Muhammed Klakan

https://github.com/lensapp/lens/issues?q=is%3Aissue+author%3Amatti+

Open Lens Terminal and meet kube control

kubectl

...
Basic Commands (Beginner):
  create          Create a resource from a file or from stdin
  expose          Take a replication controller, service, deployment or pod and expose it as a new Kubernetes service
  run             Run a particular image on the cluster
  set             Set specific features on objects

Basic Commands (Intermediate):
  explain         Get documentation for a resource
  get             Display one or many resources
  edit            Edit a resource on the server
  delete          Delete resources by file names, stdin, resources and names, or by resources and label selector

Deploy Commands:
  rollout         Manage the rollout of a resource
  scale           Set a new size for a deployment, replica set, or replication controller
...

Built-in commands or plugins

kubectl version

Let's make the first kubernetes API call

kubectl version --short

Client Version: v1.24.7
Server Version: v1.24.7-eks-fb459a0

Congrats, you have now used kubernetes.

Try without --short

kubectl version

kubeconfig

kubectl uses $HOME/.kube/config or $KUBECONFIG or --kubeconfig

$ echo $KUBECONFIG
/var/folders/gf/rlgqw8j564x8rkynfg6l498m0000gn/T/kubeconfig-9b4307491c8b92b8bbde7f8049943bb1

Lens Magic sets the

kubectl --kubeconfig PATH

Uses kubeconfig at PATH

KUBECONFIG="" kubectl

Uses $HOME/.kube/config

kubectl config

kubectl is an HTTP API client.

kubectl config view shows the contents of $KUBECONFIG (or --kubeconfig, or $HOME/.kube/config)

Lens magic

$ kubectl config view
  ...
  apiVersion: v1
  clusters:
  - cluster:
      server: http://127.0.0.1:61351/9b4307491c8b92b8bbde7f8049943bb1
  ...

Without Lens magic:

$ KUBECONFIG=$HOME/.kube/aws-eks-eu-north-1-test-1 kubectl config view
  apiVersion: v1
  clusters:
  - cluster:
      certificate-authority-data: DATA+OMITTED
      server: https://7C21A008FAEC9A53D596113221562080.yl4.eu-north-1.eks.amazonaws.com
    name: arn:aws:eks:eu-north-1:254324309357:cluster/test-1

API?

$ curl https://7C21A008FAEC9A53D596113221562080.yl4.eu-north-1.eks.amazonaws.com
  curl: (60) SSL certificate problem: unable to get local issuer certificate
  More details here: https://curl.se/docs/sslcerts.html

Kubernetes CA cert, let's ignore

curl -k https://7C21A008FAEC9A53D596113221562080.yl4.eu-north-1.eks.amazonaws.com
{
  "kind": "Status",
  "apiVersion": "v1",
  "metadata": {

  },
  "status": "Failure",
  "message": "forbidden: User \"system:anonymous\" cannot get path \"/\"",
  "reason": "Forbidden",
  "details": {

  },
  "code": 403
}%

but

$ curl -k https://7C21A008FAEC9A53D596113221562080.yl4.eu-north-1.eks.amazonaws.com/version
  {
    "major": "1",
    "minor": "22+",
    "gitVersion": "v1.22.15-eks-fb459a0",
    "gitCommit": "be82fa628e60d024275efaa239bfe53a9119c2d9",
    "gitTreeState": "clean",
    "buildDate": "2022-10-24T20:33:23Z",
    "goVersion": "go1.16.15",
    "compiler": "gc",
    "platform": "linux/amd64"
  }%

Naturally also client libraries exists https://kubernetes.io/docs/reference/using-api/client-libraries/

kubectl vs kube api version

$ KUBECONFIG=$HOME/.kube/aws-eks-eu-north-1-test-1 kubectl version --short
  Client Version: v1.24.7
  ..
  Server Version: v1.22.15-eks-fb459a0
  WARNING: version difference between client (1.24) and server (1.22) exceeds the supported minor version skew of +/-1

kubectl version can be different than server version. Some stuff just might not work or be available.

"You must use a kubectl version that is within one minor version difference of your cluster. For example, a v1.26 client can communicate with v1.25, v1.26, and v1.27 control planes. Using the latest compatible version of kubectl helps avoid unforeseen issues."

kubectl can exec commands

- name: arn:aws:eks:eu-north-1:12345678:cluster/test-1
  user:
    exec:
      apiVersion: client.authentication.k8s.io/v1beta1
      args:
      - --region
      - eu-north-1
      - eks
      - get-token
      - --cluster-name
      - test-1
      command: aws

You have reached the end of this section! Continue to the next section:

3. kubectl basics