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Kubernetes ​

Kubernetes

Kubernetes (K8s) is an open-source system for automating deployment, scaling, and management of containerized applications.

Installation ​

Docker for Mac ​

Recently Kubernetes has been included directly on the Docker app, you can activate Kubernetes on Preferences → Kubernetes → Enable Kubernetes:

Docker Kubernetes

Brew ​

bash
brew install kubernetes-cli

Useful commands ​

A Cheat Sheet can be found on the official website for more detailed information.

Cluster info ​

bash
kubectl cluster-info

Context ​

bash
kubectl config get-contexts
kubectl config set-context <context>

Namespace ​

bash
kubectl config set-context --current --namespace=<namespace>

Proxy ​

We can have a connection between our host and the Kubernetes cluster.

bash
kubectl proxy
curl http://localhost:8001/version

Nodes ​

bash
kubectl get nodes

Deployments ​

Deploy containerized applications.

Create update instances of your application.

Once the application instances are created, a Kubernetes Deployment Controller continuously monitors those instances. If the Node hosting an instance goes down or is deleted, the Deployment controller replaces the instance with an instance on another Node in the cluster.

bash
kubectl create deployment kuberenetes-bootcamp --image=gcr.io/google-samples/kubernetes-bootcamp:v1
bash
kubectl get deployments

Pods ​

Kubernetes abstraction that represents a group of one or more application containers (ex Docker) and shared resources for those containers. The resources include:

  • Shared storage, as Volumes
  • Networking, as unique cluster IP address
  • Information about how to run each container, such as the container image verison or specific ports ot use

A Pod always run on a Node.

Pods information ​

bash
kubectl get pods
kubectl describe pods

Pod name ​

bash
export POD_NAME=$(kubectl get pods -o go-template --template '{{range .items}}{{.metadata.name}}{{"\n"}}{{end}}')
echo Name of the Pod: $POD_NAME
bash
curl http://localhost:8001/api/v1/namespaces/default/pods/$POD_NAME/proxy/

Logs ​

bash
kubectl logs $POD_NAME

Execute command ​

bash
kubectl exec $POD_NAME env
kubectl exec -ti $POD_NAME bash

Services ​

Required to access to a deployment.

Services match a set of Pods using labels and selectors, a grouping primitive that allows logical operation on objects in Kubernetes.

bash
kubectl expose deployment/kubernetes-bootcamp --type="NodePort" --port 8080

# NGINX example with LoadBalancer
kubectl expose deployment nginx --port=80 --type=LoadBalancer
bash
export NODE_PORT=$(kubectl get services/kubernetes-bootcamp -o go-template='{{(index .spec.ports 0).nodePort}}')
echo NODE_PORT=$NODE_PORT
bash
curl $(minikube ip):$NODE_PORT
bash
kubectl describe deployment

Labels ​

bash
kubectl get pods -l run=kuberenetes-bootcamp
bash
kubectl get services -l run=kuberenetes-bootcamp
bash
export POD_NAME=$(kubectl get pods -o go-template --template '{{range .items}}{{.metadata.name}}{{"\n"}}{{end}}')
echo Name of the Pod: $POD_NAME
bash
kubectl get pods -l run=kuberenetes-bootcamp
bash
kubectl get pods -l run=kuberenetes-bootcamp
bash
kubectl get pods -l run=kuberenetes-bootcamp
Apply label ​
bash
kubectl label pod $POD_NAME app=v1
kubectl describe pods $POD_NAME
kubectl get pods -l app=v1

Delete ​

bash
kubectl delete service -l run=kubernetes-bootcamp
kubectl get services

Scaling ​

bash
kubectl get deployments
bash
kubectl scale deployments/kubernetes-bootcamp --replicas=4
kubectl get deployments
bash
kubectl get pods -o wide
kubectl describe deployments/kubernetes-bootcamp

Load balancing ​

bash
kubectl describe services/kubernetes-bootcamp
bash
export NODE_PORT=$(kubectl get services/kubernetes-bootcamp -o go-template='{{(index .spec.ports 0).nodePort}}')
echo NODE_PORT=$NODE_PORT
bash
curl $(minikube ip):$NODE_PORT

Rolling update ​

Update image ​

bash
kubectl set image deployments/kubernetes-bootcamp kubernetes-bootcamp=jocatalin/kubernetes-bootcamp:v2

# Check status
kubectl rollout status deployments/kubernetes-bootcamp

Rollback update ​

bash
kubectl rollout undo deployments/kubernetes-bootcamp

kubectl ​

bash
kubectl get - list resources
kubectl describe - show detailed information about a resource
kubectl logs - print the logs from a container in a pod
kubectl exec - execute a command on a container in a pod

Delete all ​

bash
kubectl delete all --all