GitHub Actions is a CI/CD (Continuous Integration and Continuous Deployment) automation tool built into GitHub. It allows you to define custom workflows for building, testing, and deploying your code when specific events occur (e.g., pushing code, creating a pull request, etc.). A workflow is a YAML-based automation script that defines a sequence of steps to be executed when triggered. Workflows are stored in the `.github/workflows/` directory of a repository.

In this section, you'll learn how to set up and use GitHub Actions to build your Docker image as well as push it to Docker Hub. You will complete the following steps:

1. Define the GitHub Actions workflow.
2. Run the workflow.

## 1. Define the GitHub Actions workflow

You can create a GitHub Actions workflow by creating a YAML file in the `.github/workflows/` directory of your repository. To do this use your favorite text editor or the GitHub web interface. The following steps show you how to create a workflow file using the GitHub web interface.

If you prefer to use the GitHub web interface, follow these steps:

1. Go to your repository on GitHub and then select the **Actions** tab.

2. Select **set up a workflow yourself**.

   This takes you to a page for creating a new GitHub Actions workflow file in
   your repository. By default, the file is created under `.github/workflows/main.yml`, let's change it name to `build.yml`.

If you prefer to use your text editor, create a new file named `build.yml` in the `.github/workflows/` directory of your repository.

Add the following content to the file:

```yaml
name: Build and push Docker image

on:
  push:
    branches:
      - main

jobs:
  build_and_push:
    runs-on: ubuntu-latest
    steps:
      - name: Login to Docker Hub
        uses: docker/login-action@v3
        with:
          username: ${{ vars.DOCKER_USERNAME }}
          password: ${{ secrets.DOCKERHUB_TOKEN }}

      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v3

      - name: Build and push
        uses: docker/build-push-action@v6
        with:
          push: true
          tags: ${{ vars.DOCKER_USERNAME }}/${{ github.event.repository.name }}:latest