kube-tutorial

This tutorial requires minikube or K3S up and running.

Namespaces

A Kubernetes namespace provides the scope for Pods, Services, and Deployments in the cluster. Users interacting with one namespace do not see the content in another namespace.

Namespaces and Quotas

Create Namespaces:

testing
development
production

with labels

customer=foo

environment={testing,development,production}

kubectl create -f https://raw.githubusercontent.com/dme86/kube-tutorial/main/namespaces.yml

Apply quotas and limitranges to testing namespace:

kubectl apply -f https://raw.githubusercontent.com/dme86/kube-tutorial/main/limitrange_quota.yml --namespace=testing

Show limitrange from testing namespace:

# only names and creation date
kubectl get limitrange --namespace=testing
# full output
kubectl get limitrange --namespace=testing --output=yaml

Show resourcequota mem-cpu-quota from testing namespace:

# short output
kubectl get resourcequota mem-cpu-quota --namespace=testing
# full yaml output
kubectl get resourcequota mem-cpu-quota --namespace=testing --output=yaml

Pods

A pod is a group of one or more containers. A container is an enclosed, self-contained execution process, much like a process in an operating system. Kubernetes uses pods to run your code and images in the cluster.

Kubernetes works with Pods, rather than containers, so that containers in the same pod can be guaranteed to run on the same machine. Containers in the same pod share their networking infrastructure, storage resources, and lifecycle.

Create a Pod

Create a simple Pod inside testing, check it's logs and expose it for access via browser:

Create example Pod

kubectl create -f https://raw.githubusercontent.com/dme86/kube-tutorial/main/pods/nginx-hello.yml --namespace=testing

Check it's logs

kubectl logs nginx-hello --namespace=testing

(if using K3S make sure your hostname is defined in /etc/hosts):

127.0.1.1 babylon.loc babylon
127.0.0.1 localhost.localdomain localhost
::1		 localhost6.localdomain6 localhost6

Show Pod-Infos

kubectl get pods --namespace=testing -o wide

Get a Pod description

kubectl describe po nginx-hello --namespace=testing

Expose

kubectl expose pod nginx-hello --type=NodePort --port=8080 --target-port=80 --namespace=testing

Get url and port

minikube service nginx-hello --url --namespace=testing

(or if using K3S):

kubectl get service -n testing

Try to create a second pod from the pods folder. The service will expose both pods, see:

kubectl describe service --namespace=testing

Accessing the pod via browser you'll see the Server name - either nginx-hello or nginx-hello-2. Delete the container wich is displayed on the website and reload: Kubernetes will automatically route the traffic to the other (healthy) container.

Delete a Pod

kubectl delete pod nginx-hello --namespace=testing

Deployments

A deployment is an object in Kubernetes that lets you manage a set of identical pods.

Without a deployment, you’d need to create, update, and delete a bunch of pods manually.

With a deployment, you declare a single object in a YAML file. This object is responsible for creating the pods, making sure they stay up to date, and ensuring there are enough of them running

You can also easily autoscale your applications using a Kubernetes deployment.

Create a Deployment

This will create a simple deployment with the same container we used in the Pods section inside our development namespace:

kubectl apply -f https://raw.githubusercontent.com/dme86/kube-tutorial/main/deployments/nginx-deployment.yml --namespace=development

Check your deployment:

kubectl get deployments --namespace=development

Now you can effortlessly scale up or down the amount of containers in your deployment:

kubectl scale --replicas=6 deployment nginx-hello --namespace=development