1. Introduction

In this tutorial, we will learn how to integrate Kubernetes with Jenkins CI/CD. Continuous Integration (CI) and Continuous Delivery (CD) embody a culture, set of operating principles, and collection of practices that enable application development teams to deliver code changes more frequently and reliably. Jenkins is a self-contained, open-source automation server which can be used to automate all sorts of tasks related to building, testing, and delivering or deploying software. Kubernetes, on the other hand, is an open-source system for automating deployment, scaling, and management of containerized applications.

You will learn how to set up a Jenkins CI/CD pipeline to build Docker images and deploy them into a Kubernetes cluster.

Prerequisites

• Basic understanding of Jenkins and Kubernetes.
• A working Jenkins and Kubernetes installation.
• Docker installed on the Jenkins server.

2. Step-by-Step Guide

Jenkins Configuration

Before we start, we need to make sure that Jenkins has the Kubernetes Continuous Deploy plugin installed. This will allow Jenkins to deploy updates to Kubernetes directly after the build process.

1. Go to Manage Jenkins > Manage Plugins > Available.
2. Search for the 'Kubernetes Continuous Deploy' plugin and install it.

Jenkinsfile

Jenkins uses a 'Jenkinsfile' to define a pipeline. We will use this file to define the steps of our CI/CD process. Here's a basic example of what this file might look like:

pipeline {
  agent any
  stages {
    stage('Build') {
      steps {
        echo 'Building...'
      }
    }
    stage('Test') {
      steps {
        echo 'Testing...'
      }
    }
    stage('Deploy') {
      steps {
        echo 'Deploying...'
      }
    }
  }
}

Each stage in this pipeline represents a part of the software's life cycle. Our job is to fill these stages with life.

Building Docker Images

The first stage of our pipeline will be used to build Docker images. For this, we will use the Docker Pipeline plugin.

1. Install the Docker Pipeline plugin via Manage Jenkins > Manage Plugins > Available.
2. Add the following to the 'Build' stage in your Jenkinsfile:

stage('Build') {
  steps {
    script {
      dockerImage = docker.build("my-image:${env.BUILD_ID}")
    }
  }
}

This will build a Docker image using the Dockerfile found in the root directory of your project and tag it with the current build ID.

3. Code Examples

Deploying to Kubernetes

Now that we have our Docker image, we can deploy it to our Kubernetes cluster. For this, we will use the Kubernetes CLI.

Add the following to the 'Deploy' stage in your Jenkinsfile:

stage('Deploy') {
  steps {
    script {
      kubernetesDeploy(configs: 'k8s/*.yaml', kubeconfigId: 'my-kubeconfig', enableConfigSubstitution: true)
    }
  }
}

This configuration will deploy all Kubernetes configurations found in the 'k8s' directory of your project. It uses a kubeconfig file with the ID 'my-kubeconfig', which should be added to Jenkins as a secret file.

The 'enableConfigSubstitution' option allows us to use environment variables in our Kubernetes configurations.

4. Summary

In this tutorial, we've learned how to set up a Jenkins CI/CD pipeline that builds Docker images and deploys them into a Kubernetes cluster. This allows for a smooth, automated deployment process that ensures your software is always up to date.

For further learning, consider exploring more advanced Jenkins and Kubernetes concepts, such as Jenkins shared libraries and Kubernetes deployments.

5. Practice Exercises

1. Modify the pipeline to include a 'Staging' step, which deploys the application to a staging environment before deploying to production.
2. Add a rollback mechanism to the pipeline, which reverts the application to a previous state if the deployment fails.
3. Implement automated testing in the pipeline, which prevents the application from being deployed if any tests fail.

Remember, practice is key when learning new concepts. Don't be afraid to experiment and make mistakes, as they are a crucial part of the learning process.