Jenkins is all about configuration because it needs to control jobs, environment, tools, plugins, and pipelines. Let’s break it down step by step.

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📌 Types of Configuration in Jenkins

Jenkins has multiple layers of configuration:

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1. Global Configuration (Manage Jenkins → Configure System)

• Applies to the entire Jenkins server.

• Things you configure here:

  • JDK, Maven, Gradle installations

  • Git, SVN credentials

  • Email notifications (SMTP)

  • Environment variables

  • Plugins (e.g., Slack, SonarQube, Docker)

• Example: Set up Maven so all jobs can use it.

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2. Job/Project Configuration

• Specific to each job (Freestyle, Maven, Pipeline, Multibranch).

• Configurable items:

  • Source Code Management (Git, SVN)

  • Build triggers (Poll SCM, Webhooks, Schedule with CRON)

  • Build steps (Run Maven goals, Execute shell/Windows batch)

  • Post-build actions (Email, Deploy, Archive artifacts, Publish reports)

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3. Node/Agent Configuration (Distributed Builds)

• Jenkins can run builds on multiple nodes (agents/slaves).

• Configuration includes:

  • Labels (e.g., "Windows", "Linux", "Docker")

  • Remote root directory

  • Launch method (SSH, JNLP, Docker, Cloud)

• Helps distribute workload (e.g., run Selenium tests on multiple OS).

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4. Plugin Configuration

• Every plugin has its own config.

• Examples:

  • Allure plugin → Reporting setup

  • Slack plugin → Webhook URL for notifications

  • GitHub plugin → Token & repo details

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5. Pipeline Configuration

• In scripted or declarative pipelines (Jenkinsfile).

• Configurations include:

  • Stages (Build → Test → Deploy)

  • Agent selection (agent any or agent { label 'linux' })

  • Tools (maven, jdk, nodejs)

  • Environment variables (env.BROWSER = "chrome")

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6. Security & User Configuration

• Manage Jenkins → Configure Global Security.

• Options:

  • Authentication (LDAP, AD, GitHub, SSO)

  • Authorization (Matrix-based, Role-based strategy)

  • Credentials (username/password, SSH keys, API tokens)

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7. Build Environment Configuration

• Inside job settings.

• Example:

  • Delete workspace before build

  • Inject environment variables

  • Use secret credentials in builds

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📌 Summary Table

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✅ In short:

• Global config → applies to whole Jenkins

• Job config → applies only to a specific job

• Node config → applies to build agents

• Pipeline config → written in Jenkinsfile

• Plugin & Security config → extend functionality