Jenkins: Credentials & Agents

This tutorial extends Jenkins pipeline knowledge with two enterprise essentials:

• credentials (secure secret management)
• agents/nodes (running the right stage in the right place)

1) Jenkins credentials: avoid hardcoding

Jenkins stores secrets in its credentials system. You reference them by credentialsId.

Common credential types:

• Secret text (token)
• Username/password
• SSH keys
• Files (e.g., kubeconfig)

Example: secret text token

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

Rules of thumb:

• do not print the token
• avoid set -x
• keep logs clean

2) Agents: choose where stages run

Declarative: label-based

pipeline {
  agent none

  stages {
    stage('Build') {
      agent { label 'linux-x64' }
      steps {
        sh 'npm ci'
        sh 'npm run build'
      }
    }

    stage('Test') {
      agent { label 'linux-x64' }
      steps {
        sh 'npm test'
      }
    }
  }
}

Declarative: Docker agent

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

  stages {
    stage('Build') {
      steps {
        sh 'npm ci'
        sh 'npm run build'
      }
    }
  }
}

3) Artifacts: keep outputs for later

Archive artifacts so you can download them from the build page.

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

4) Practical pipeline example (theory + code)

A typical CI flow:

1. checkout
2. install deps
3. build
4. test
5. archive artifacts

pipeline {
  agent any

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

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

    stage('Build') {
      steps { sh 'npm run build' }
    }

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

    stage('Archive') {
      steps { archiveArtifacts artifacts: 'dist/**', fingerprint: true }
    }
  }
}

Next steps

Next tutorials:

• Monitoring & Observability fundamentals
• Terraform for reproducible environments
• Ansible for idempotent configuration