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Use Kubectl

Kubectl (ou kube control) est le CLI de base pour controller les cluster Kubernetes.

Comme chaque actions passe obligatoirement par "l'API Server", cela permet de faire des Opérations sur des Ressouces en sélectionnant un Format de son choix.

Les opérations basiques​

  • apply/create - create resoucre(s)
  • run - start a pod from an image
  • explain - documentation of resources
  • delete - delete resource(s)
  • get - list resources
  • describe - detailed resource information
  • exec - execute a command on a container (like docker exec)
  • logs - view logs on a container

More info here: https://kubernetes.io/docs/reference/kubectl/overview/#operations

Les ressources basiques​

  • Nodes (no)
  • Pods (po)
  • Services (svc)

Many more here: https://kubernetes.io/docs/reference/kubectl/overview/#resource-types

Les formats​

  • wide - output additional info to stdout
  • yaml - YAML formatted API object
  • json - JSON formatted API object

How work Kubectl​

img

More info here: https://kubernetes.io/docs/reference/kubectl/kubectl and here: https://kubernetes.io/docs/reference/kubectl/cheatsheet/

Basic commands​

# Basic cluster info
kubectl cluster-info 
# Basic status and roles
kubectl get nodes
# Additional information
kubectl get nodes -o wide
# List of pods in the default namespace
kubectl get pods
# List of system pods
kubectl get pods --namespace kube-system
# Additionnal info for each pod
kubectl get pods --namespace kube-system -o wide
# List all
kubectl get all --all-namespaces | more
# api-resources list all the resources available in the cluster
kubectl api-resources
# Limit the number of rows
kubectl api-resources | head -n 10
# Filter easily
kubectl api-resources | grep pod
# Then we can get info on a specific api-resources
kubectl explain pod | more
# You can go deeper
kubectl explain.spec pod | more
kubectl explain.spec.containers pod | more
# It work with alias
kubectl explain no
# Take a closer look at our Nodes
kubectl describe nodes c1-master1
kubectl describe nodes c1-node1

Bash completion​

Pour les plus flemmards 😄 (en vrai c'est vraiment pratique)

sudo apt-get install -y bash-completion
echo "source <(kubectl completion bash)" >> ~/.bashrc
source ~/.bashrc
# Test it
kubectl g[tab][tab] po[tab][tab] --all[tab][tab]
kubectl -h | more
kubectl get -h | more
kubectl describe -h | more