Jenkins.md

Jenkins Cheatsheet

1. Introduction:

• Jenkins is an open-source automation server that helps automate parts of software development related to building, testing, and deploying, facilitating continuous integration and delivery.

2. Installation:

• Docker Installation:

  docker run -d -p 8080:8080 -p 50000:50000 jenkins/jenkins:lts

• Direct Installation:

  • For Ubuntu/Debian:

    wget -q -O - https://pkg.jenkins.io/debian/jenkins.io.key | sudo apt-key add -
    sudo sh -c 'echo deb http://pkg.jenkins.io/debian-stable binary/ > /etc/apt/sources.list.d/jenkins.list'
    sudo apt update
    sudo apt install jenkins

  • For CentOS/RHEL:

    sudo wget -O /etc/yum.repos.d/jenkins.repo https://pkg.jenkins.io/redhat-stable/jenkins.repo
    sudo rpm --import https://pkg.jenkins.io/redhat-stable/jenkins.io.key
    sudo yum install jenkins

• Access Jenkins:

  • Visit http://localhost:8080 in your web browser.

3. Jenkins Pipeline:

• Declarative Pipeline:

  pipeline {
      agent any
      environment {
          MY_VAR = "value"
      }
      stages {
          stage('Checkout') {
              steps {
                  checkout scm
              }
          }
          stage('Build') {
              steps {
                  sh 'make'
              }
          }
          stage('Test') {
              steps {
                  sh 'make test'
              }
          }
          stage('Deploy') {
              steps {
                  sh 'make deploy'
              }
          }
      }
      post {
          success {
              echo 'Pipeline completed successfully!'
          }
          failure {
              echo 'Pipeline failed.'
          }
      }
  }

• Scripted Pipeline:

  node {
      stage('Checkout') {
          checkout scm
      }
      stage('Build') {
          sh 'make'
      }
      stage('Test') {
          sh 'make test'
      }
      stage('Deploy') {
          sh 'make deploy'
      }
  }

4. Common Jenkins Commands:

• Restart Jenkins:

  sudo systemctl restart jenkins

• Manage Jenkins from CLI:

  java -jar jenkins-cli.jar -s http://localhost:8080/ list-jobs

5. Useful Jenkins Plugins:

• Blue Ocean: Modern UI for Jenkins pipelines.
• Git: Integrate Git version control into Jenkins.
• Pipeline: Enables Pipeline as Code.
• Credentials Binding: Securely manage credentials.
• SonarQube Scanner: Integrate code quality checks.
• Slack Notification: Send pipeline status notifications to Slack.

6. Best Practices:

• Pipeline as Code: Always use Jenkins Pipelines defined in Jenkinsfile for consistent and version-controlled builds.

• Use Parameters: Use parameters to make your pipelines flexible and reusable.

  parameters {
      string(name: 'ENV', defaultValue: 'dev', description: 'Environment')
  }

• Secure Jenkins: Regularly update plugins, use RBAC, and secure the Jenkins instance with HTTPS.

7. Jenkins Configuration:

• Manage Jenkins:
  • Manage and configure global settings from the Jenkins dashboard under Manage Jenkins.
• Configure Tools: Set up JDK, Maven, and other tools globally in Global Tool Configuration.
• Jenkinsfile Configuration:
  • Define your pipeline stages, environment, and agents within a Jenkinsfile stored in your repository.

8. Advanced Jenkins:

• Parallel Stages:

  pipeline {
      agent any
      stages {
          stage('Parallel') {
              parallel {
                  stage('Unit Tests') {
                      steps {
                          sh 'make test'
                      }
                  }
                  stage('Integration Tests') {
                      steps {
                          sh 'make integration-test'
                      }
                  }
              }
          }
      }
  }

• Shared Libraries: Centralize and reuse pipeline code across projects using Shared Libraries.

Troubleshooting

Common Issues

1. Jenkins Won't Start

   # Check logs
   sudo tail -f /var/log/jenkins/jenkins.log
   
   # Check permissions
   sudo chown -R jenkins:jenkins /var/lib/jenkins

2. Pipeline Failure

   // Add error handling
   pipeline {
       agent any
       stages {
           stage('Build') {
               steps {
                   script {
                       try {
                           sh 'make build'
                       } catch (exc) {
                           echo 'Build failed!'
                           throw exc
                       }
                   }
               }
           }
       }
   }

3. Plugin Issues

   • Clear plugin cache:

     rm -rf $JENKINS_HOME/plugins/*.jpi
     rm -rf $JENKINS_HOME/plugins/*.hpi

   • Restart Jenkins after plugin updates

Useful Plugins

1. Pipeline

   • Pipeline Graph View
   • Pipeline Stage View
   • Blue Ocean

2. Source Control

   • Git
   • GitHub Integration
   • BitBucket Integration

3. Build Tools

   • Maven Integration
   • Gradle
   • NodeJS

4. Testing

   • JUnit
   • Cobertura
   • SonarQube Scanner

5. Deployment

   • Docker
   • Kubernetes
   • AWS