# Jenkins — The Original Open-Source Automation Server

> Jenkins is the original and still widely-used open-source automation server for CI/CD. 2000+ plugins, pipeline-as-code via Jenkinsfile, distributed builds, and first-class support for nearly every build tool. The battle-tested choice for enterprise CI.

## Install

Save as a script file and run:

## Quick Use

```bash
# Docker
docker run -d --name jenkins -p 8080:8080 -p 50000:50000 \
  -v jenkins-data:/var/jenkins_home \
  jenkins/jenkins:lts-jdk17

# Get initial admin password
docker exec jenkins cat /var/jenkins_home/secrets/initialAdminPassword

# Visit http://localhost:8080 and complete setup
```

Create a Jenkinsfile in your repo:
```groovy
pipeline {
  agent any

  environment {
    NODE_VERSION = "20"
  }

  stages {
    stage("Checkout") {
      steps { checkout scm }
    }
    stage("Install") {
      steps { sh "npm ci" }
    }
    stage("Test") {
      steps { sh "npm test" }
      post {
        always {
          junit "test-results/*.xml"
        }
      }
    }
    stage("Build") {
      steps { sh "npm run build" }
    }
    stage("Deploy") {
      when { branch "main" }
      steps { sh "./deploy.sh production" }
    }
  }

  post {
    failure {
      slackSend channel: "#ci", message: "Build failed: ${env.BUILD_URL}"
    }
  }
}
```

## Intro

Jenkins is the original open-source automation server. Created as Hudson in 2004 by Kohsuke Kawaguchi at Sun Microsystems, forked to Jenkins in 2011. Jenkins still powers a huge portion of the worldwide CI/CD workload, especially in enterprise environments thanks to its 2000+ plugin ecosystem and extreme customizability.

- **Repo**: https://github.com/jenkinsci/jenkins
- **Stars**: 25K+
- **Language**: Java
- **License**: MIT

## What Jenkins Does

- **Pipelines** — Jenkinsfile (Groovy) declarative or scripted
- **Freestyle jobs** — GUI-configured legacy jobs
- **Distributed builds** — controller + agents on multiple machines
- **Plugins** — 2000+ for source control, build tools, deploy targets, notifications
- **Multibranch** — auto-discover branches and PRs
- **Shared libraries** — reusable Groovy libraries across pipelines
- **Credentials store** — encrypted secrets management
- **Blue Ocean** — modern pipeline UI
- **CloudBees integrations** — enterprise extensions

## Architecture

Jenkins controller hosts the UI, scheduler, and job configuration. Agents (formerly slaves) execute builds in parallel, connected via JNLP, SSH, or Kubernetes pods. Pipelines are checkpointed — survive controller restarts.

## Self-Hosting

```yaml
# docker-compose.yml
version: "3"
services:
  jenkins:
    image: jenkins/jenkins:lts-jdk17
    ports: ["8080:8080", "50000:50000"]
    volumes:
      - jenkins-data:/var/jenkins_home
    environment:
      JAVA_OPTS: "-Djenkins.install.runSetupWizard=false"
volumes:
  jenkins-data:
```

## Key Features

- Pipeline-as-code (Jenkinsfile)
- 2000+ plugins
- Distributed builds
- Matrix builds
- Shared libraries
- Credentials store
- Email/Slack/Teams notifications
- Multi-branch pipelines
- Auto-scaling agents on Kubernetes
- LDAP, SAML, OAuth auth

## Comparison

| CI/CD | Hosted | Pipeline | Ecosystem |
|---|---|---|---|
| Jenkins | Self-hosted | Jenkinsfile | Largest |
| GitHub Actions | Cloud + self-hosted runners | YAML | Huge |
| GitLab CI | Cloud + self-hosted | YAML | Large |
| CircleCI | Cloud + enterprise | YAML | Large |
| Drone | Self-hosted | YAML | Medium |
| Woodpecker | Self-hosted | YAML | Growing |

## 常见问题 FAQ

**Q: Jenkins 是不是过时了？**
A: 被 GitHub Actions、GitLab CI 抢走了大量新项目。但 Jenkins 在企业（尤其是有存量 pipeline、严格合规要求）仍然是首选。2000+ plugin 无出其右。

**Q: 和 GitHub Actions 比？**
A: Actions 云原生、YAML 简洁、与 GitHub 深度集成；Jenkins 自托管、Groovy 灵活、插件生态无敌。选择看托管偏好和集成需求。

**Q: 性能和内存？**
A: Java 应用，controller 通常至少 2GB 堆。大规模部署（百万 job）需要调优 JVM 和存储。

## 来源与致谢 Sources

- Docs: https://www.jenkins.io/doc
- GitHub: https://github.com/jenkinsci/jenkins
- License: MIT

---
Source: https://tokrepo.com/en/workflows/0114181b-35f7-11f1-9bc6-00163e2b0d79
Author: Script Depot