Jenkins CI: Pipeline Basics

Jenkins is a CI server that automates build/test/release workflows. Even if you use it less today, understanding Jenkins pipeline concepts helps you reason about CI systems generally.

Theory first: pipelines as executable delivery design

A CI pipeline is an executable model of your delivery process. Each stage encodes a quality boundary (build, test, security, deploy), and failures represent policy violations—not just broken scripts.

This framing keeps Jenkins practical: you are designing trustworthy flow control for change, where feedback speed and reproducibility matter as much as successful builds.

Learning outcomes

By the end you can:

• understand Jenkins pipeline stages
• run commands in steps
• use agents/nodes to control execution environment

1) Pipeline overview

A Jenkins pipeline is a script describing what to run and when. Today, declarative pipelines are most common.

2) Minimal declarative pipeline

Jenkinsfile:

pipeline {
  agent any

  stages {
    stage('Checkout') {
      steps {
        checkout scm
      }
    }

    stage('Install') {
      steps {
        sh 'npm ci'
      }
    }

    stage('Test') {
      steps {
        sh 'npm test'
      }
    }
  }
}

3) Common stage patterns

Lint + test

stage('Lint') {
  steps { sh 'npm run lint' }
}

stage('Test') {
  steps { sh 'npm test' }
}

Build + archive

stage('Build') {
  steps {
    sh 'npm run build'
    archiveArtifacts artifacts: 'dist/**', fingerprint: true
  }
}

4) Choosing an execution environment

Declarative pipeline:

agent {
  docker {
    image 'node:20-alpine'
    args '-u node'
  }
}

Or run on specific labeled agents:

agent { label 'linux-x64' }

5) Secrets and credentials (conceptual)

Jenkins uses a credentials store so you don’t hardcode secrets in the Jenkinsfile. Common usage pattern is withCredentials.

Example (concept):

withCredentials([string(credentialsId: 'API_TOKEN', variable: 'API_TOKEN')]) {
  sh 'curl -H "Authorization: Bearer $API_TOKEN" https://api.example.com'
}

Next steps

Next tutorials:

• Jenkins credentials + artifacts
• Multi-stage releases
• Pair with monitoring: alerts on pipeline failures