Jenkins | DevOps QuickRef | DevOps QuickRef

Jenkins pipelines are defined as code in a Jenkinsfile, checked into the repo alongside the application. The declarative syntax below covers what you'll touch in almost every pipeline.

Minimal Pipeline

pipeline {
    agent any
 
    stages {
        stage('Build') {
            steps {
                sh 'npm ci && npm run build'
            }
        }
        stage('Test') {
            steps {
                sh 'npm test'
            }
        }
    }
}

Declarative vs. scripted

Declarative pipeline (the pipeline { } block above) is the standard, structured syntax — predictable, easier to lint, and what most teams should default to. Scripted pipeline (node { }, raw Groovy) is more flexible but harder to review — reach for it only when declarative syntax genuinely can't express what you need.

Agents

pipeline {
    agent { label 'linux && docker' }
    // or per-stage:
    stages {
        stage('Build') {
            agent { docker { image 'node:20' } }
            steps { sh 'npm ci' }
        }
    }
}

agent none

Set agent none at the pipeline level when every stage declares its own agent — it stops Jenkins reserving an executor for the top level that no step actually uses.

Environment Variables

pipeline {
    agent any
    environment {
        NODE_ENV = 'production'
        API_URL  = "${params.API_URL ?: 'https://api.example.com'}"
    }
    stages {
        stage('Build') {
            steps { sh 'echo $NODE_ENV' }
        }
    }
}

Credentials

stage('Deploy') {
    steps {
        withCredentials([usernamePassword(
            credentialsId: 'registry-creds',
            usernameVariable: 'REG_USER',
            passwordVariable: 'REG_PASS'
        )]) {
            sh 'docker login -u $REG_USER -p $REG_PASS registry.example.com'
        }
    }
}

Never echo a credential

withCredentials masks the bound variables in console output automatically — but only for exact matches. Don't concatenate or transform a secret before printing it (e.g. echo "token=$REG_PASS" inside a larger string built another way), since masking can't catch what it doesn't recognize verbatim.

Parallel Stages

stage('Test') {
    parallel {
        stage('Unit') {
            steps { sh 'npm run test:unit' }
        }
        stage('Integration') {
            steps { sh 'npm run test:integration' }
        }
    }
}

Conditional Stages

stage('Deploy') {
    when {
        branch 'main'
    }
    steps {
        sh './deploy.sh'
    }
}

Post Actions

pipeline {
    agent any
    stages { /* ... */ }
    post {
        always  { junit 'reports/**/*.xml' }
        success { slackSend(message: 'Build passed') }
        failure { slackSend(message: 'Build failed') }
    }
}

Artifacts

archiveArtifacts artifacts: 'dist/**', fingerprint: true

Saves build output as a Jenkins artifact, downloadable from the build page and fingerprinted for traceability across later builds.

Useful CLI Commands

jenkins-cli build JOB_NAME

Triggers a job build from the command line, useful for scripting outside the Jenkins UI.

jenkins-cli console JOB_NAME

Streams a running or completed build's console output.

Troubleshooting

Common pipeline failures

Stuck in queue — no executor matches the requested agent label; check node labels against the pipeline. Credential not found — the credentialsId doesn't exist in the scope the pipeline runs in (global vs. folder-scoped credentials). Workspace conflicts — two builds of the same job sharing a workspace path; enable disableConcurrentBuilds() or use a per-build workspace.