learning-kubernetes

• Install minikube

./install-minukube.sh

• Start minikube (enable v1alpha1)

minikube start --nodes=2 \
               --memory='4000mb' \
               --cpus=4 \
               --disk-size=10g \
               --driver=kvm2 \
               --extra-config=apiserver.runtime-config=settings.k8s.io/v1alpha1=true

• Configure

kubectl config use-context minikube

Delete

minikube delete --all=true --purge=true

Enable loadbalancer

• See what changes would be made, returns nonzero returncode if different

kubectl get configmap kube-proxy -n kube-system -o yaml | \
  sed -e "s/strictARP: false/strictARP: true/" | \
  kubectl diff -f - -n kube-system
kubectl get configmap kube-proxy -n kube-system -o yaml | \
  sed -e "s/mode: \"\"/mode: \"ipvs\"/" | \
  kubectl diff -f - -n kube-system

• Actually apply the changes, returns nonzero returncode on errors only

kubectl get configmap kube-proxy -n kube-system -o yaml | \
  sed -e "s/strictARP: false/strictARP: true/" | \
  kubectl apply -f - -n kube-system
kubectl get configmap kube-proxy -n kube-system -o yaml | \
  sed -e "s/mode: \"\"/mode: \"ipvs\"/" | \
  kubectl apply -f - -n kube-system

• Install metallb

kubectl apply -f https://raw.githubusercontent.com/metallb/metallb/v0.9.3/manifests/namespace.yaml
kubectl apply -f https://raw.githubusercontent.com/metallb/metallb/v0.9.3/manifests/metallb.yaml
# On first install only
kubectl create secret generic -n metallb-system memberlist --from-literal=secretkey="$(openssl rand -base64 128)"

• Configmap

MINIKUBE_IP=$(minikube ip)
export MINIKUBE_BASE_IP=${MINIKUBE_IP%.*}
cat <<EOF | kubectl create -f -
apiVersion: v1
kind: ConfigMap
metadata:
  namespace: metallb-system
  name: config
data:
  config: |
    address-pools:
    - name: default
      protocol: layer2
      addresses:
      - ${MINIKUBE_BASE_IP}.95-${MINIKUBE_BASE_IP}.105
EOF

• Get cm: kubectl -n metallb-system get cm config

• reference: https://metallb.universe.tf/installation

Useful commands

• kubectl get pod - get information about all runnning pods
• kubectl describe pod <pod> - describe one pod
• kubectl expose pod <pod> --port=444 --name=frontend - expose the port of a pod (creates a new service)
• kubectl port-forward <pod> 8080 - port forward the exposed pod port to your local machine
• kubectl attach <pod> -i - attach to the pod
• kubectl exec <pod> -- command - Execute a command on the pod
• kubectl label pods <pod> my label=awesome - Add a new label to a pod
• kubectl run -i --tty busybox --image=busybox --restart=Never -- sh - Run a shell in a pod - very useful for debugging
• kubectl get deployments - get information on current deployments
• kubectl get rs - get information about replica sets
• kubectl get pods --show-labels - get pods, and also show labels attached to those pods
• kubectl set image deployment/helloworld-deployment k8s-demo=k8s-demo:2 - run k8s-demo with the image label version 2
• kubectl edit deployment/helloworld-deployment - edit the deployment object
• kubectl rollout status deployment/helloworld-deployment - get the status of the rollout
• kubectl rollout history deployment/helloworld-deployment - get the history of the rollout
• kubectl rollout undo deployment/helloworld-deployment - rollback to previous version
• kubectl rollout undo deployment/helloworld-deployment --to-revision=n - rollback to any version
• kubectl explain pods or kubectl explain pod.spec documentation
• watch -n1 "kubectl get all -o wide --show-labels"
• kubectl logs pod my-name --previous to show previous restarted pod
• kubectl api-resources show all resources
• kubectl drain <node name> and kubectl uncordon <node name> safely drain node
• kubectl create -f kubia-deployment-v1.yaml --record, kubectl set image deployment kubia nodejs=luksa/kubia:v2, kubectl rollout undo deployment kubia and kubectl rollout history deployment kubia
• properties: revisionHistoryLimit and minReadySeconds
• kubectl rollout pause deployment kubia and kubectl rollout resume deployment kubia
• kubectl get pods --all-namespaces -o wide --field-selector spec.nodeName=<node-name>

NOTE Although most objects' names must conform to the naming conventions specified in RFC 1035 (Domain names), which means they may contain only letters, digits, dashes, and dots, namespaces (and a few others) aren't allowed to contain dots.

References

• https://kubernetes.io/docs/reference/kubectl/cheatsheet/
• Calico on minikube