How to build and push a Docker image using GitHub actions ๐Ÿค–

How to build and push a Docker image using GitHub actions ๐Ÿค–

Because creating an automated pipeline can save time

Sep 8, 2022ยท

4 min read

In this tutorial, we will use an automated pipeline to build Docker images and then push them to a remote registry. For this example, we will use Docker Hub.

As always, here is the official documentation link for GitHub actions.

Prerequisites

Before we start implementing our pipeline, we need to set up our container registry and GitHub repository.

Docker Hub

Our action will require access to a Docker Hub repository. The preferred method of authentication is the use of an access token. Here's what you need to do:

  1. Create an account on Docker Hub
  2. Create a repository with the desired name of your image
  3. Click on Account settings -> Privacy, and generate a new access token.

Note: Make sure to save the token's value because it will not appear again after a page refresh.

GitHub

Select a GitHub repository where you want to implement the automated action and follow these steps:

  1. Click on Settings -> Secrets -> Actions and select New repository secret.
  2. Create a secret named DOCKERHUB_USERNAME and add your Docker Hub username as a value.
  3. Create another one named DOCKERHUB_TOKEN and add your Docker Hub access token that you generated earlier as a value.

Creating our action

Once we have the container registry and GitHub repo set up, we can create the workflow file. To do that:

  1. Go to your GitHub repository and click on the tab Actions.
  2. There you will find some suggested pre-built workflows, and an option to set up a workflow yourself. Click on that.

Writting the file

Each workflow is represented by a .yml document.

Below is our Docker image build and push .yml file.

name: Docker image build and push

on:
  push:
    branches: [ "master" ]
  pull-request:

jobs:

  build-push:

    runs-on: ubuntu-latest
    steps:
      - name: Checkout
        uses: actions/checkout@v3

      - name: Login to DockerHub
        uses: docker/login-action@v2
        with:
          username: ${{ secrets.DOCKERHUB_USERNAME }}
          password: ${{ secrets.DOCKERHUB_TOKEN }}

      - name: Build and push
        uses: docker/build-push-action@v3
        with:
          context: .
          push: true
          tags: <username>/<repository>:latest

Here's what's going on:

  1. name: The name of your GitHub action.
  2. on: Controls when your action will run.
  3. push: and pull-request: Triggers the workflow on every push request at the master branch, and every pull-request.
  4. jobs: A workflow consists of one or many jobs that can run sequentially or in parallel. For this example, we only use one job named build-push
  5. runs-on: The OS you want for the runner environment that executes the workflow. For this example, we will use Ubuntu as it has Docker pre-configured. Other popular options are windows-latest or macos-latest.
  6. steps: Each step runs in its own process in the runner environment. Steps consist of:

    • name: Describes each step.
    • uses: Selects a pre-built action to run as part of a step in your job.

      For example here we are using the actions/checkout@v3, docker/login-action@v2 and docker/build-push-action@v3, as part of our workflow.

      You can also use any custom action from the GitHub actions marketplace.

    • with: Input parameters for this step's pre-built action.

      For example, in the second step, we pass as parameters a username: and password:. Notice how the values are drawn from the repository secrets that we set up earlier.

      In the third step, we have a context: parameter that indicates the location of our Dockerfile, a push: parameter set to true and a tags: parameter where we can define what tags we want for our Docker Hub repository.

More on GitHub actions syntax here.

Deploying the workflow

That was it! ๐ŸŽ‰

All that's left to do is deploy our action for the first time, and we can do that by committing this file to our repository. This will save it under .github/workflows/docker-image.yml, and trigger the workflow.

After the image gets built, it will be uploaded to your Docker Hub repository with the tag :latest.

You can find the overview of each workflow under the Actions tab on your GitHub repository, as well as a detailed log of each job step.

Till next time! โœŒ๏ธ

ย