Jenkins Cheatsheet

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Installation & Setup

Linux Installation

Install Jenkins on Ubuntu/Debian systems.

# Update package manager and install Java
sudo apt update
sudo apt install fontconfig openjdk-21-jre
java -version
# Add Jenkins GPG key
sudo wget -O /usr/share/keyrings/jenkins-keyring.asc \
https://pkg.jenkins.io/debian-stable/jenkins.io-2023.key
# Add Jenkins repository
echo "deb [signed-by=/usr/share/keyrings/jenkins-keyring.asc]" \
https://pkg.jenkins.io/debian-stable binary/ | sudo tee \
/etc/apt/sources.list.d/jenkins.list > /dev/null
# Install Jenkins
sudo apt update && sudo apt install jenkins
# Start Jenkins service
sudo systemctl start jenkins
sudo systemctl enable jenkins

Windows & macOS

Install Jenkins using installers or package managers.

# Windows: Download Jenkins installer from jenkins.io
# Or use Chocolatey
choco install jenkins
# macOS: Use Homebrew
brew install jenkins-lts
# Or download directly from:
# https://www.jenkins.io/download/
# Start Jenkins service
brew services start jenkins-lts

Post-Installation Setup

Initial configuration and unlock Jenkins.

# Get initial admin password
sudo cat /var/lib/jenkins/secrets/initialAdminPassword
# Or for Docker installations
docker exec jenkins_container cat /var/jenkins_home/secrets/initialAdminPassword
# Access Jenkins web interface
# Browse to http://localhost:8080
# Enter the initial admin password
# Install suggested plugins or select custom plugins

Initial Configuration

Complete the setup wizard and create admin user.

# After unlocking Jenkins:
# 1. Install suggested plugins (recommended)
# 2. Create first admin user
# 3. Configure Jenkins URL
# 4. Start using Jenkins
# Verify Jenkins is running
sudo systemctl status jenkins
# Check Jenkins logs if needed
sudo journalctl -u jenkins.service

Basic Jenkins Operations

Access Jenkins: Web Interface & CLI Setup

Access Jenkins through browser and set up CLI tools.

# Access Jenkins web interface
http://localhost:8080
# Download Jenkins CLI
wget http://localhost:8080/jnlpJars/jenkins-cli.jar
# Test CLI connection
java -jar jenkins-cli.jar -s http://localhost:8080 help
# List available commands
java -jar jenkins-cli.jar -s http://localhost:8080 help

Job Creation: create-job / Web UI

Create new build jobs using CLI or web interface.

# Create job from XML configuration
java -jar jenkins-cli.jar -auth user:token create-job my-job < job-config.xml
# Create simple freestyle job via web UI:
# 1. Click "New Item"
# 2. Enter job name
# 3. Select "Freestyle project"
# 4. Configure build steps
# 5. Save configuration

List Jobs: list-jobs

View all configured jobs in Jenkins.

# List all jobs
java -jar jenkins-cli.jar -auth user:token list-jobs
# List jobs with pattern matching
java -jar jenkins-cli.jar -auth user:token list-jobs "*test*"
# Get job configuration
java -jar jenkins-cli.jar -auth user:token get-job my-job > job-config.xml

Job Management

Build Jobs: build

Trigger and manage job builds.

# Build a job
java -jar jenkins-cli.jar -auth user:token build my-job
# Build with parameters
java -jar jenkins-cli.jar -auth user:token build my-job -p PARAM=value
# Build and wait for completion
java -jar jenkins-cli.jar -auth user:token build my-job -s -v
# Build and follow console output
java -jar jenkins-cli.jar -auth user:token build my-job -f
Quiz

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What does the -s flag do in jenkins-cli.jar build my-job -s?
Skips the build
Waits for the build to complete (synchronous)
Shows build status
Stops the build

Job Control: enable-job / disable-job

Enable or disable jobs.

# Enable a job
java -jar jenkins-cli.jar -auth user:token enable-job my-job
# Disable a job
java -jar jenkins-cli.jar -auth user:token disable-job my-job
# Check job status in web UI
# Navigate to job dashboard
# Look for "Disable/Enable" button
Quiz

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What happens when you disable a Jenkins job?
The job is deleted permanently
The job configuration is preserved but it won't run automatically
The job is moved to a different folder
All build history is deleted

Job Deletion: delete-job

Remove jobs from Jenkins.

# Delete a job
java -jar jenkins-cli.jar -auth user:token delete-job my-job
# Bulk delete jobs (with caution)
for job in job1 job2 job3; do
  java -jar jenkins-cli.jar -auth user:token delete-job $job
done

Console Output: console

View build logs and console output.

# View latest build console output
java -jar jenkins-cli.jar -auth user:token console my-job
# View specific build number
java -jar jenkins-cli.jar -auth user:token console my-job 15
# Follow console output in real-time
java -jar jenkins-cli.jar -auth user:token console my-job -f
Quiz

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What does the -f flag do in jenkins-cli.jar console my-job -f?
Forces the build to stop
Shows only failed builds
Follows the console output in real-time
Formats the output as JSON

Pipeline Management

Pipeline Creation

Create and configure Jenkins pipelines.

// Basic Jenkinsfile (Declarative Pipeline)
pipeline {
    agent any

    stages {
        stage('Build') {
            steps {
                echo 'Building application...'
                sh 'make build'
            }
        }

        stage('Test') {
            steps {
                echo 'Running tests...'
                sh 'make test'
            }
        }

        stage('Deploy') {
            steps {
                echo 'Deploying application...'
                sh 'make deploy'
            }
        }
    }
}

Pipeline Syntax

Common pipeline syntax and directives.

// Scripted Pipeline syntax
node {
    stage('Checkout') {
        checkout scm
    }

    stage('Build') {
        sh 'make build'
    }

    stage('Test') {
        sh 'make test'
        junit 'target/test-results/*.xml'
    }
}
// Parallel execution
stages {
    stage('Parallel Tests') {
        parallel {
            stage('Unit Tests') {
                steps {
                    sh 'make unit-test'
                }
            }
            stage('Integration Tests') {
                steps {
                    sh 'make integration-test'
                }
            }
        }
    }
}

Pipeline Configuration

Advanced pipeline configuration and options.

// Pipeline with post-build actions
pipeline {
    agent any

    stages {
        stage('Build') {
            steps {
                sh 'make build'
            }
        }
    }

    post {
        always {
            echo 'This always runs'
        }
        success {
            echo 'Build succeeded'
        }
        failure {
            echo 'Build failed'
            emailext subject: 'Build Failed',
                     body: 'Build failed',
                     to: 'team@company.com'
        }
    }
}

Pipeline Triggers

Configure automatic pipeline triggers.

// Pipeline with triggers
pipeline {
    agent any

    triggers {
        // Poll SCM every 5 minutes
        pollSCM('H/5 * * * *')

        // Cron-like scheduling
        cron('H 2 * * *')  // Daily at 2 AM

        // Upstream job trigger
        upstream(upstreamProjects: 'upstream-job',
                threshold: hudson.model.Result.SUCCESS)
    }

    stages {
        stage('Build') {
            steps {
                sh 'make build'
            }
        }
    }
}

Plugin Management

Plugin Installation: CLI

Install plugins using command line interface.

# Install plugin via CLI (requires restart)
java -jar jenkins-cli.jar -auth user:token install-plugin git
# Install multiple plugins
java -jar jenkins-cli.jar -auth user:token install-plugin \
  git maven-plugin docker-plugin
# Install from .hpi file
java -jar jenkins-cli.jar -auth user:token install-plugin \
  /path/to/plugin.hpi
# List installed plugins
java -jar jenkins-cli.jar -auth user:token list-plugins
# Plugin installation via plugins.txt (for Docker)
# Create plugins.txt file:
git:latest
maven-plugin:latest
docker-plugin:latest
pipeline-stage-view:latest
# Use jenkins-plugin-cli tool
jenkins-plugin-cli --plugins git maven-plugin docker-plugin

Essential Plugins

Commonly used Jenkins plugins for different purposes.

# Build & SCM Plugins
git                    # Git integration
github                 # GitHub integration
maven-plugin          # Maven build support
gradle                # Gradle build support
# Pipeline Plugins
workflow-aggregator   # Pipeline plugin suite
pipeline-stage-view   # Pipeline stage view
blue-ocean           # Modern UI for pipelines
# Deployment & Integration
docker-plugin        # Docker integration
kubernetes           # Kubernetes deployment
ansible              # Ansible automation
# Quality & Testing
junit                # JUnit test reports
jacoco              # Code coverage
sonarqube           # Code quality analysis

Plugin Management Web UI

Manage plugins through Jenkins web interface.

# Access Plugin Manager:
# 1. Navigate to Manage Jenkins
# 2. Click "Manage Plugins"
# 3. Use Available/Installed/Updates tabs
# 4. Search for plugins
# 5. Select and install
# 6. Restart Jenkins if required
# Plugin update process:
# 1. Check "Updates" tab
# 2. Select plugins to update
# 3. Click "Download now and install after restart"

User Management & Security

User Management

Create and manage Jenkins users.

# Enable Jenkins security:
# 1. Manage Jenkins → Configure Global Security
# 2. Enable "Jenkins' own user database"
# 3. Allow users to sign up (initial setup)
# 4. Set authorization strategy
# Create user via CLI (requires appropriate permissions)
# Users are typically created via web UI:
# 1. Manage Jenkins → Manage Users
# 2. Click "Create User"
# 3. Fill user details
# 4. Assign roles/permissions

Authentication & Authorization

Configure security realms and authorization strategies.

# Security configuration options:
# 1. Security Realm (how users authenticate):
#    - Jenkins' own user database
#    - LDAP
#    - Active Directory
#    - Matrix-based security
#    - Role-based authorization
# 2. Authorization Strategy:
#    - Anyone can do anything
#    - Legacy mode
#    - Logged-in users can do anything
#    - Matrix-based security
#    - Project-based Matrix Authorization

API Tokens

Generate and manage API tokens for CLI access.

# Generate API token:
# 1. Click username → Configure
# 2. API Token section
# 3. Click "Add new Token"
# 4. Enter token name
# 5. Generate and copy token
# Use API token with CLI
java -jar jenkins-cli.jar -auth username:api-token \
  -s http://localhost:8080 list-jobs
# Store credentials securely
echo "username:api-token" > ~/.jenkins-cli-auth
chmod 600 ~/.jenkins-cli-auth

Credentials Management

Manage stored credentials for jobs and pipelines.

# Manage credentials via CLI
java -jar jenkins-cli.jar -auth user:token \
  list-credentials system::system::jenkins
# Create credentials XML and import
java -jar jenkins-cli.jar -auth user:token \
  create-credentials-by-xml system::system::jenkins \
  < credential.xml

// Access credentials in pipelines
withCredentials([usernamePassword(
  credentialsId: 'my-credentials',
  usernameVariable: 'USERNAME',
  passwordVariable: 'PASSWORD'
)]) {
  sh 'docker login -u $USERNAME -p $PASSWORD'
}

Build Monitoring & Troubleshooting

Build Status & Logs

Monitor build status and access detailed logs.

# Check build status
java -jar jenkins-cli.jar -auth user:token console my-job
# Get build info
java -jar jenkins-cli.jar -auth user:token get-job my-job
# Monitor build queue
# Web UI: Jenkins Dashboard → Build Queue
# Shows pending builds and their status
# Build history access
# Web UI: Job → Build History
# Shows all previous builds with status

System Information

Get Jenkins system information and diagnostics.

# System information
java -jar jenkins-cli.jar -auth user:token version
# Node information
java -jar jenkins-cli.jar -auth user:token list-computers
# Groovy console (admin only)
# Manage Jenkins → Script Console
# Execute Groovy scripts for system info:
println Jenkins.instance.version
println Jenkins.instance.getRootDir()
println System.getProperty("java.version")

Log Analysis

Access and analyze Jenkins system logs.

# System logs location
# Linux: /var/log/jenkins/jenkins.log
# Windows: C:\Program Files\Jenkins\jenkins.out.log
# View logs
tail -f /var/log/jenkins/jenkins.log
# Log levels configuration
# Manage Jenkins → System Log
# Add new log recorder for specific components
# Common log locations:
sudo journalctl -u jenkins.service     # Systemd logs
sudo cat /var/lib/jenkins/jenkins.log  # Jenkins log file

Performance Monitoring

Monitor Jenkins performance and resource usage.

# Built-in monitoring
# Manage Jenkins → Load Statistics
# Shows executor utilization over time
# JVM monitoring
# Manage Jenkins → Manage Nodes → Master
# Shows memory, CPU usage, and system properties
# Build trends
# Install "Build History Metrics" plugin
# View build duration trends and success rates
# Disk usage monitoring
# Install "Disk Usage" plugin
# Monitor workspace and build artifact storage

Jenkins Configuration & Settings

Global Configuration

Configure global Jenkins settings and tools.

# Global Tool Configuration
# Manage Jenkins → Global Tool Configuration
# Configure:
# - JDK installations
# - Git installations
# - Maven installations
# - Docker installations
# System Configuration
# Manage Jenkins → Configure System
# Set:
# - Jenkins URL
# - System message
# - # of executors
# - Quiet period
# - SCM polling limits

Environment Variables

Configure Jenkins environment variables and system properties.

# Built-in environment variables
BUILD_NUMBER          # Build number
BUILD_ID              # Build ID
JOB_NAME             # Job name
WORKSPACE            # Job workspace path
JENKINS_URL          # Jenkins URL
NODE_NAME            # Node name
# Custom environment variables
# Manage Jenkins → Configure System
# Global properties → Environment variables
# Add key-value pairs for global access

Jenkins Configuration as Code

Manage Jenkins configuration using JCasC plugin.

# JCasC configuration file (jenkins.yaml)
jenkins:
  systemMessage: "Jenkins configured as code"
  numExecutors: 4
  securityRealm:
    local:
      allowsSignup: false
      users:
       - id: "admin"
         password: "admin123"
# Apply configuration
# Set CASC_JENKINS_CONFIG environment variable
export CASC_JENKINS_CONFIG=/path/to/jenkins.yaml

Best Practices

Security Best Practices

Keep your Jenkins instance secure and production-ready.

# Security recommendations:
# 1. Enable security and authentication
# 2. Use matrix-based authorization
# 3. Regular security updates
# 4. Limit user permissions
# 5. Use API tokens instead of passwords
# Secure Jenkins configuration:
# - Disable CLI over remoting
# - Use HTTPS with valid certificates
# - Regular backup of JENKINS_HOME
# - Monitor security advisories
# - Use credential plugins for secrets

Performance Optimization

Optimize Jenkins for better performance and scalability.

# Performance tips:
# 1. Use distributed builds with agents
# 2. Optimize build scripts and dependencies
# 3. Clean up old builds automatically
# 4. Use pipeline libraries for reusability
# 5. Monitor disk space and memory usage
# Build optimization:
# - Use incremental builds where possible
# - Parallel execution of stages
# - Artifact caching
# - Workspace cleanup
# - Resource allocation tuning
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