🚀 Day 11 of 30 Days of DevOps Interview Preparation – GitHub Actions: Basic Workflow YAML

Series: 30 Days DevOps Interview Preparation
Author: Tathagat Gaikwad

In this post, we dive into GitHub Actions — a native CI/CD tool that allows developers to automate, customize, and execute workflows right from their GitHub repositories.
By the end, you’ll know:

• How to write a basic workflow YAML.

• How to trigger pipelines based on Git events.

• How to integrate with AWS for real deployments.

• Common interview questions & answers on GitHub Actions.

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🔍 1. What is GitHub Actions?

GitHub Actions is a CI/CD and automation service tightly integrated with GitHub. It helps you automate tasks like:

• Running tests on every commit.

• Deploying applications to cloud environments.

• Building Docker images.

• Running scheduled maintenance scripts.

Key Components:

• Workflow: Defined in .github/workflows/*.yml — contains automation rules.

• Event: Triggers the workflow (push, pull_request, workflow_dispatch, schedule).

• Job: A group of steps executed in the same environment.

• Step: An individual task (command or prebuilt action).

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📄 2. Basic GitHub Actions Workflow YAML

Let’s create a Node.js CI workflow that runs tests on every push to the main branch.

name: Node.js CI

on:
  push:
    branches:
      - main

jobs:
  build:
    runs-on: ubuntu-latest

    steps:
      - name: Checkout repository
        uses: actions/checkout@v3

      - name: Set up Node.js
        uses: actions/setup-node@v3
        with:
          node-version: '18'

      - name: Install dependencies
        run: npm install

      - name: Run tests
        run: npm test

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☁ 3. Practical AWS Deployment with GitHub Actions

Here’s a real-world workflow for deploying to AWS EC2 after tests pass.

name: Deploy to AWS EC2

on:
  push:
    branches:
      - main

jobs:
  deploy:
    runs-on: ubuntu-latest

    steps:
      - name: Checkout repository
        uses: actions/checkout@v3

      - name: Set up Node.js
        uses: actions/setup-node@v3
        with:
          node-version: '18'

      - name: Install dependencies
        run: npm install

      - name: Run tests
        run: npm test

      - name: Deploy to AWS EC2
        env:
          HOST: ${{ secrets.AWS_HOST }}
          USER: ${{ secrets.AWS_USER }}
          KEY: ${{ secrets.AWS_SSH_KEY }}
        run: |
          echo "$KEY" > key.pem
          chmod 400 key.pem
          scp -i key.pem -o StrictHostKeyChecking=no ./build.zip $USER@$HOST:/home/ec2-user/
          ssh -i key.pem -o StrictHostKeyChecking=no $USER@$HOST "unzip -o build.zip && pm2 restart app"

How to set secrets in GitHub:

1. Go to your repository → Settings → Secrets and variables → Actions.

2. Add:

   • AWS_HOST → EC2 public IP

   • AWS_USER → ec2-user (Amazon Linux) or ubuntu (Ubuntu)

   • AWS_SSH_KEY → Private SSH key for EC2

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💡 4. Why This Matters in Interviews

Interviewers expect you to know:

• How workflows are structured (on, jobs, steps).

• The difference between self-hosted runners and GitHub-hosted runners.

• How to handle secrets securely in GitHub Actions.

• How to integrate GitHub Actions with cloud providers.

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🛠 5. Common GitHub Actions Interview Questions

Q1: How do you trigger a GitHub Action only for a specific branch?
A: Use on: push: branches: [branch-name].

Q2: Where do you store sensitive credentials?
A: In GitHub Secrets (Settings → Secrets and variables → Actions).

Q3: How do you run multiple jobs in parallel?
A: Define multiple jobs under jobs: without dependencies.

Q4: What’s the difference between workflow_dispatch and push?
A: push runs automatically when code is pushed; workflow_dispatch triggers manually via GitHub UI or API.

Q5: How do you reuse workflows across repositories?
A: Use the workflow_call event to define reusable workflows.

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📌 6. Key Takeaways

• YAML is your automation recipe.

• Always store sensitive values in Secrets.

• Separate build, test, and deploy steps.

• Integrate GitHub Actions with AWS, Docker, or Kubernetes for real deployments.

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💻 GitHub Repository: DevOps Interview Preparation
📝 Previous Post: Day 10 – Jenkins Git Trigger Pipeline

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