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Kubernetes Tutorial

Kubernetes, often referred to as "K8s," is an open-source container orchestration platform for automating the deployment, scaling, and management of containerized applications. This tutorial provides a basic guide to Kubernetes concepts, components, and common commands.

1. Key Concepts in Kubernetes​

Cluster​

A Kubernetes cluster is a set of nodes where containerized applications run. It includes:

  • Master Node: Manages the cluster, schedules workloads, and handles API requests.
  • Worker Nodes: Nodes where the application containers run.

Pods​

A pod is the smallest deployable unit in Kubernetes, usually running one or more containers.

Services​

A service exposes an application running on a set of pods to external or internal traffic.

Deployments​

A deployment manages a set of identical pods to ensure they stay running and updated.

2. Setting Up Kubernetes​

To start using Kubernetes, you need access to a Kubernetes cluster.

Local Setup with Minikube​

  1. Install Minikube: Follow the installation guide at Minikube.

  2. Start Minikube:

    minikube start

  3. Verify Installation:

    kubectl get nodes

This command should show a list of nodes, with Minikube as the single node.

3. Basic Kubernetes Commands​

kubectl​

The kubectl command-line tool is used to manage Kubernetes clusters.

Common Commands​

  • Get Nodes: List all nodes in the cluster.

    kubectl get nodes

  • Get Pods: List all pods in the default namespace.

    kubectl get pods

  • Get Services: List all services.

    kubectl get services

4. Creating a Deployment​

A deployment describes an application to be deployed, including its container image and desired state.

Example Deployment YAML​

Save the following YAML as nginx-deployment.yaml:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.14.2
        ports:
        - containerPort: 80

Apply the Deployment​

kubectl apply -f nginx-deployment.yaml

View the Deployment​

kubectl get deployments

5. Exposing a Service​

To expose your deployment, create a service that routes traffic to the pods.

Example Service YAML​

Save the following YAML as nginx-service.yaml:

apiVersion: v1
kind: Service
metadata:
  name: nginx-service
spec:
  type: LoadBalancer
  selector:
    app: nginx
  ports:
  - protocol: TCP
    port: 80
    targetPort: 80

Apply the Service​

kubectl apply -f nginx-service.yaml

Get Service Details​

kubectl get services

6. Scaling a Deployment​

To scale the number of replicas in a deployment:

kubectl scale deployment nginx-deployment --replicas=5

Verify the scaling with:

kubectl get pods

7. Updating a Deployment​

To update a deployment, edit the container image:

kubectl set image deployment/nginx-deployment nginx=nginx:1.16.0

Check the rollout status:

kubectl rollout status deployment/nginx-deployment

8. Deleting Resources​

To delete a resource:

  • Delete Deployment:

    kubectl delete deployment nginx-deployment

  • Delete Service:

    kubectl delete service nginx-service

Summary​

This tutorial covered the basics of Kubernetes:

  1. Setting up a cluster with Minikube.
  2. Creating, scaling, and updating deployments.
  3. Exposing applications with services.

Kubernetes simplifies managing containerized applications, allowing you to scale and orchestrate applications across clusters efficiently.

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