Quiz: Docker and CI/CD

Test your knowledge on Docker, Docker Compose, and GitHub Actions.

30 questions - Click on each question to reveal the answer.

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Questions 1-15: Docker

Question 1: What is Docker?

Answer: Docker is a containerization platform that allows packaging an application with all its dependencies into a lightweight and portable container. Advantages:

• Same environment everywhere
• Application isolation
• Fast deployment
• Scalability

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Question 2: What is the difference between an image and a container?

Answer:

• Image: read-only template (like a class)
• Container: running instance of an image (like an object)

# Create a container from an image
docker run -d --name my-app my-image:1.0

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Question 3: How to write a Dockerfile for Spring Boot?

Answer:

FROM eclipse-temurin:21-jdk-alpine

WORKDIR /app

COPY target/*.jar app.jar

EXPOSE 8080

ENTRYPOINT ["java", "-jar", "app.jar"]

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Question 4: How to optimize a Dockerfile with multi-stage build?

Answer:

# Stage 1: Build
FROM maven:3.9-eclipse-temurin-21 AS build
WORKDIR /app
COPY pom.xml .
RUN mvn dependency:go-offline
COPY src ./src
RUN mvn package -DskipTests

# Stage 2: Run
FROM eclipse-temurin:21-jre-alpine
WORKDIR /app
COPY --from=build /app/target/*.jar app.jar
EXPOSE 8080
ENTRYPOINT ["java", "-jar", "app.jar"]

Final image is smaller (no Maven, full JDK).

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Question 5: How to build and run a Docker image?

Answer:

# Build the image
docker build -t my-app:1.0 .

# Run
docker run -d -p 8080:8080 --name my-app my-app:1.0

# View logs
docker logs -f my-app

# Stop
docker stop my-app

# Remove
docker rm my-app

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Question 6: How to pass environment variables to the container?

Answer:

# In command line
docker run -e SPRING_PROFILES_ACTIVE=prod \
           -e DB_HOST=postgres \
           my-app:1.0

# With a file
docker run --env-file .env my-app:1.0

# .env
SPRING_PROFILES_ACTIVE=prod
DB_HOST=postgres
DB_PASSWORD=secret

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Question 7: How to persist data with Docker?

Answer: With volumes:

# Named volume
docker run -v postgres-data:/var/lib/postgresql/data postgres

# Bind mount
docker run -v $(pwd)/data:/app/data my-app

Data survives container deletion.

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Question 8: How to connect containers to each other?

Answer: With a Docker network:

# Create a network
docker network create my-network

# Connect containers
docker run -d --name postgres --network my-network postgres
docker run -d --name app --network my-network \
           -e DB_HOST=postgres my-app

# Containers find each other by name

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Question 9: What is Docker Compose?

Answer: Tool to define and run multi-container applications:

# docker-compose.yml
services:
  app:
    build: .
    ports:
      - "8080:8080"
    depends_on:
      - postgres
    environment:
      - SPRING_DATASOURCE_URL=jdbc:postgresql://postgres:5432/mydb
  
  postgres:
    image: postgres:15
    volumes:
      - postgres-data:/var/lib/postgresql/data
    environment:
      - POSTGRES_DB=mydb
      - POSTGRES_USER=user
      - POSTGRES_PASSWORD=pass

volumes:
  postgres-data:

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Question 10: What are the main Docker Compose commands?

Answer:

# Start all services
docker compose up -d

# View logs
docker compose logs -f

# Stop
docker compose stop

# Remove (with volumes)
docker compose down -v

# Rebuild
docker compose up -d --build

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Question 11: How to configure a Docker healthcheck?

Answer:

HEALTHCHECK --interval=30s --timeout=3s --start-period=60s --retries=3 \
  CMD curl -f http://localhost:8080/actuator/health || exit 1

Or in docker-compose.yml:

services:
  app:
    healthcheck:
      test: ["CMD", "curl", "-f", "http://localhost:8080/actuator/health"]
      interval: 30s
      timeout: 3s
      retries: 3
      start_period: 60s

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Question 12: How to limit a container's resources?

Answer:

services:
  app:
    deploy:
      resources:
        limits:
          cpus: '1'
          memory: 512M
        reservations:
          cpus: '0.5'
          memory: 256M

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Question 13: How to view containers and images?

Answer:

# Running containers
docker ps

# All containers
docker ps -a

# Images
docker images

# Disk usage
docker system df

# Clean up
docker system prune -a

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Question 14: How to debug a container?

Answer:

# Logs
docker logs my-app

# Shell into the container
docker exec -it my-app /bin/sh

# Inspect the container
docker inspect my-app

# Real-time stats
docker stats my-app

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Question 15: How to push an image to a registry?

Answer:

# Docker Hub
docker login
docker tag my-app:1.0 username/my-app:1.0
docker push username/my-app:1.0

# GitHub Container Registry
docker login ghcr.io
docker tag my-app:1.0 ghcr.io/username/my-app:1.0
docker push ghcr.io/username/my-app:1.0

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Questions 16-30: CI/CD with GitHub Actions

Question 16: What is GitHub Actions?

Answer: CI/CD automation platform integrated with GitHub:

• Workflows triggered by events
• Hosted or self-hosted runners
• Marketplace of reusable actions
• Secure secrets and variables

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Question 17: How to structure a GitHub Actions workflow?

Answer:

# .github/workflows/ci.yml
name: CI Pipeline

on:
  push:
    branches: [main]
  pull_request:
    branches: [main]

jobs:
  build:
    runs-on: ubuntu-latest
    
    steps:
      - uses: actions/checkout@v4
      
      - name: Set up JDK
        uses: actions/setup-java@v4
        with:
          java-version: '21'
          distribution: 'temurin'
      
      - name: Build with Maven
        run: mvn clean package

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Question 18: How to run tests in CI?

Answer:

jobs:
  test:
    runs-on: ubuntu-latest
    
    steps:
      - uses: actions/checkout@v4
      
      - name: Set up JDK
        uses: actions/setup-java@v4
        with:
          java-version: '21'
          distribution: 'temurin'
          cache: 'maven'
      
      - name: Run tests
        run: mvn test
      
      - name: Upload test results
        uses: actions/upload-artifact@v4
        if: always()
        with:
          name: test-results
          path: target/surefire-reports/

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Question 19: How to use Maven cache?

Answer:

- uses: actions/setup-java@v4
  with:
    java-version: '21'
    distribution: 'temurin'
    cache: 'maven'  # Automatic cache

# Or manually
- uses: actions/cache@v4
  with:
    path: ~/.m2/repository
    key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}
    restore-keys: |
      ${{ runner.os }}-maven-

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Question 20: How to build and push a Docker image?

Answer:

jobs:
  docker:
    runs-on: ubuntu-latest
    
    steps:
      - uses: actions/checkout@v4
      
      - name: Log in to GitHub Container Registry
        uses: docker/login-action@v3
        with:
          registry: ghcr.io
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}
      
      - name: Build and push
        uses: docker/build-push-action@v5
        with:
          context: .
          push: true
          tags: ghcr.io/${{ github.repository }}:${{ github.sha }}

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Question 21: How to use GitHub secrets?

Answer:

jobs:
  deploy:
    runs-on: ubuntu-latest
    
    steps:
      - name: Deploy to server
        env:
          SSH_KEY: ${{ secrets.SSH_PRIVATE_KEY }}
          DB_PASSWORD: ${{ secrets.DB_PASSWORD }}
        run: |
          echo "$SSH_KEY" > key.pem
          chmod 600 key.pem
          ssh -i key.pem user@server "deploy.sh"

Secrets are masked in logs.

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Question 22: How to run jobs in parallel?

Answer:

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - run: mvn test
  
  lint:
    runs-on: ubuntu-latest
    steps:
      - run: mvn checkstyle:check
  
  security:
    runs-on: ubuntu-latest
    steps:
      - run: mvn dependency-check:check

By default, jobs run in parallel.

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Question 23: How to create dependencies between jobs?

Answer:

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - run: mvn package
  
  test:
    needs: build  # Waits for build to finish
    runs-on: ubuntu-latest
    steps:
      - run: mvn test
  
  deploy:
    needs: [build, test]  # Waits for both
    runs-on: ubuntu-latest
    steps:
      - run: ./deploy.sh

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Question 24: How to use a matrix to test multiple versions?

Answer:

jobs:
  test:
    runs-on: ubuntu-latest
    strategy:
      matrix:
        java: [17, 21]
        os: [ubuntu-latest, windows-latest]
    
    steps:
      - uses: actions/setup-java@v4
        with:
          java-version: ${{ matrix.java }}
          distribution: 'temurin'
      
      - run: mvn test

Runs 4 jobs (2 versions x 2 OS).

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Question 25: How to trigger a workflow manually?

Answer:

on:
  workflow_dispatch:
    inputs:
      environment:
        description: 'Environment to deploy'
        required: true
        default: 'staging'
        type: choice
        options:
          - staging
          - production

jobs:
  deploy:
    runs-on: ubuntu-latest
    steps:
      - run: echo "Deploying to ${{ inputs.environment }}"

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Question 26: How to use GitHub environments?

Answer:

jobs:
  deploy-staging:
    environment: staging
    runs-on: ubuntu-latest
    steps:
      - run: ./deploy.sh ${{ vars.SERVER_URL }}
  
  deploy-production:
    needs: deploy-staging
    environment:
      name: production
      url: https://myapp.com
    runs-on: ubuntu-latest
    steps:
      - run: ./deploy.sh ${{ vars.SERVER_URL }}

Environments can have:

• Specific secrets
• Approval rules
• Wait timers

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Question 27: How to check code quality?

Answer:

jobs:
  quality:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      
      - name: SonarCloud Scan
        uses: SonarSource/sonarcloud-github-action@master
        env:
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
          SONAR_TOKEN: ${{ secrets.SONAR_TOKEN }}
      
      - name: Check coverage
        run: |
          mvn jacoco:report
          COVERAGE=$(grep -oP 'Total.*?([0-9]+)%' target/site/jacoco/index.html | grep -oP '[0-9]+')
          if [ "$COVERAGE" -lt 70 ]; then exit 1; fi

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Question 28: How to deploy to a server?

Answer:

jobs:
  deploy:
    runs-on: ubuntu-latest
    steps:
      - name: Deploy via SSH
        uses: appleboy/ssh-action@master
        with:
          host: ${{ secrets.HOST }}
          username: ${{ secrets.USERNAME }}
          key: ${{ secrets.SSH_KEY }}
          script: |
            cd /app
            docker compose pull
            docker compose up -d

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Question 29: How to notify the team of the result?

Answer:

jobs:
  notify:
    runs-on: ubuntu-latest
    needs: [build, test, deploy]
    if: always()
    
    steps:
      - name: Slack Notification
        uses: slackapi/slack-github-action@v1
        with:
          channel-id: 'deployments'
          slack-message: |
            Deployment ${{ needs.deploy.result }}
            Commit: ${{ github.sha }}
            Author: ${{ github.actor }}
        env:
          SLACK_BOT_TOKEN: ${{ secrets.SLACK_TOKEN }}

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Question 30: What are the best CI/CD practices?

Answer:

1. Fail fast: stop as soon as a test fails
2. Aggressive caching: Maven dependencies, Docker images
3. Parallelize: independent tests in parallel
4. Secure secrets: never in plain text
5. Separate environments: staging before production
6. Automatic rollback: in case of failure
7. Notifications: Slack, email for failures
8. Artifacts: save test reports
9. Semantic versioning: tags for releases
10. Branch protection: mandatory reviews

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Score

Score	Level
27-30	Excellent - Mastered Docker and CI/CD
21-26	Good - Some revisions needed
15-20	Average - Review the chapters
Less than 15	Needs improvement

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