🔧 GitLab CI/CD Basics – Understanding Stages & Runners 🚢

In IT, automation is the key to ensuring smooth software development and deployment. GitLab CI/CD provides a powerful way to automate building, testing, and deploying applications using pipelines.

💡 Think of GitLab CI/CD as an airport security system 🏢✈️. Every passenger (code update) must go through multiple security checks (build & test stages) before boarding the plane (deployment).

✅ What You’ll Learn Today:

✔ What GitLab CI/CD is and why it’s important
✔ Understanding stages, jobs, and runners
✔ How to create a CI/CD pipeline in GitLab
✔ Running a real-world example pipeline

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📌 What is GitLab CI/CD?

GitLab CI/CD is an automation tool that helps developers:
🔹 Automatically test and build applications when code is pushed
🔹 Ensure software quality before deployment
🔹 Deploy applications efficiently with fewer errors

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❌ Challenges Without CI/CD:

• Manual testing & deployments lead to delays and errors

• Bugs go unnoticed until production, affecting users

• Inconsistent environments make debugging difficult

✅ With GitLab CI/CD:
✔ Every code update is automatically tested
✔ Builds and deployments are consistent across environments
✔ Developers get faster feedback on issues

📌 Real-World Analogy: CI/CD as a Fast-Food Kitchen 🍔🚀

• The kitchen (CI/CD pipeline) follows a structured process

• Orders (code updates) go through preparation (build) and quality checks (test)

• If everything is good, they are delivered to customers (deployment)

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🏗 1️⃣ Understanding GitLab CI/CD Components

GitLab CI/CD uses a .gitlab-ci.yml file to define automation workflows. Let’s break down its key components:

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🔄 2️⃣ Understanding GitLab CI/CD Stages

A stage in GitLab CI/CD is a step in the pipeline, like build, test, or deploy.

📜 Example: CI/CD Stages for a Node.js App

stages:
  - build
  - test
  - deploy

build_job:
  stage: build
  script:
    - echo "Building the application..."
    - npm install

test_job:
  stage: test
  script:
    - echo "Running tests..."
    - npm test

deploy_job:
  stage: deploy
  script:
    - echo "Deploying to production..."
    - ./deploy.sh

🎯 What Happens in Each Stage?

📌 Real-World Analogy: Stages as an Automated Factory Process 🏭

• Build Stage = Raw materials are collected and assembled

• Test Stage = Quality checks are performed

• Deploy Stage = Finished products are sent to customers

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⚙️ 3️⃣ What Are GitLab Runners?

Runners are servers that execute CI/CD pipeline jobs.

📌 Real-World Analogy: Runners as Kitchen Staff 🍳

• Shared Runners = Freelance chefs working on multiple restaurant orders

• Specific Runners = Chefs dedicated to a single restaurant

• Group Runners = Chefs preparing meals for multiple branches of a restaurant

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🚀 4️⃣ Setting Up a GitLab CI/CD Pipeline

🔹 Step 1: Create a .gitlab-ci.yml File

Inside your GitLab repository, create a new file:

.gitlab-ci.yml

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🔹 Step 2: Define the Pipeline Stages

Copy and paste the following YAML configuration:

stages:
  - build
  - test
  - deploy

build_app:
  stage: build
  script:
    - echo "Building the application..."
    - npm install

test_app:
  stage: test
  script:
    - echo "Running tests..."
    - npm test

deploy_app:
  stage: deploy
  script:
    - echo "Deploying to production..."
    - ./deploy.sh

📌 How It Works:
✔ Build Stage – Installs dependencies
✔ Test Stage – Runs unit tests
✔ Deploy Stage – Pushes the application to production

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🔧 5️⃣ Setting Up a GitLab Runner for Your Project

🔹 Step 1: Install GitLab Runner

sudo apt update
sudo apt install gitlab-runner

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🔹 Step 2: Register a New Runner

gitlab-runner register

📌 You’ll be prompted to enter:
✔ GitLab URL – Your GitLab instance URL
✔ Runner Token – Found under Settings > CI/CD > Runners
✔ Runner Type – Choose shell, docker, or Kubernetes

📌 Now, your GitLab Runner is ready to execute CI/CD jobs!

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🌍 6️⃣ Deploying Applications with GitLab CI/CD

🔹 Deploying to AWS S3 (Static Website Hosting)

GitLab CI/CD can deploy static websites to AWS S3 automatically.

📌 Example Deployment Job:

deploy:
  stage: deploy
  script:
    - aws s3 sync ./build s3://my-s3-bucket --delete
  environment:
    name: production

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🔹 Deploying Docker Containers with GitLab CI/CD

Many IT teams deploy applications using Docker for better scalability.

📌 Example Deployment Job for Docker:

deploy:
  stage: deploy
  script:
    - docker build -t my-app:latest .
    - docker push my-dockerhub-user/my-app:latest

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🏆 7️⃣ Best Practices for GitLab CI/CD

✅ Use Caching – Speed up pipelines by caching dependencies
✅ Run Tests Before Deployment – Catch bugs early
✅ Use Secrets for Credentials – Never hardcode API keys
✅ Monitor Pipeline Performance – Optimize execution time
✅ Enable Rollbacks – Rollback strategies for failed deployments

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🏁 Final Thoughts – Why GitLab CI/CD Matters?

🔹 Automates software testing, building, and deployment
🔹 Reduces manual errors and speeds up releases
🔹 Improves software quality through standardized workflows

📌 Next Up: Advanced GitLab CI/CD – Multi-Stage Pipelines & Security Best Practices! 🚀

💬 Got questions? Drop them below! Let’s discuss! 😊