Using GitHub Actions to automatically build Docker images

4 min readMar 27, 2024

When we use cloud resources we usually face the challenge that performance is enough to run a containerised application but it is not enough to build it from scratch, especially if during the build, we need to create binaries as well.

Github Actions can help us a lot, connecting it to dockerhub will make our process totally effortless.

The steps:
1. Create a repository on GitHub
2. Create a repository on dockerhub
3. Create an Access Token on dockerhub
4. Add the Access Token to the GitHub repository
5. Create the “Action”
6. Upload the Dockerfile

1. Create new public/private repository on GitHub

2. Create new public/private repository on dockerhub

Set a name and description to your repo

3. Create an Access Token on dockerhub

Click on your avatar on the top right corner, then “My account”

In the ‘Security” menu, click on “New Access Token”

Set a description to your new token , then save the token as it is displayed only once

4. Add the Access Token to your GitHub repository

Navigate to “Settings”

We need to set credentials for our GitHub Actions under “Secrets and Variables”
Click on “New repository secret”

Create “DOCKERHUB_TOKEN” and paste the Access Token you got on dockerhub

Create “DOCKERHUB_USERNAME” and add your username

6. Create a new Action

Add the following script:

name: Build and push Docker image to dockerhub

on:
  push:
    branches: [ "main" ]
    
jobs:

  build:

    runs-on: ubuntu-latest

    steps:
    - name: Check out the repo
      uses: actions/checkout@v4

    - name: Login to dockerhub
      uses: docker/login-action@v3
      with:
       username: ${{ secrets.DOCKERHUB_USERNAME }}
       password: ${{ secrets.DOCKERHUB_TOKEN }}

    - name: Build and push to dockerhub
      uses: docker/build-push-action@v5
      with:
       context:
       push: true
       tags: kicsipixel/githubaction:latest

6. Upload the Dockerfile

Clone the repository to your machine:

git clone https://github.com/kicsipixel/GitHubAction.git

Add the your Dockerfile. Here I use a simple one:

#This is a very simple, sample Image 
FROM ubuntu 

RUN apt-get update 
CMD [“echo”,”Image created”]

Add and commit it:

git add .

git commit -m "Dockerfile was added

Push it to GitHub:

git push origin main

You can see that the Action automatically runs, when you push to ‘main’ branch.

Once the build is successful, you have the image on dockerhub

As you can see it is very easy to create some automation with GitHub, we use anyway for version controlling. This way you can save time and resources in your deployment environment by usiong pre-built image in your docker-compose.yml file like this:

services:
  app:
    image: kicsipixel/githubaction:latest

Note: Consider use a different branch than ‘main’ in your Action script to avoid rebuild the image every time when you change something in your repo.

Update: In case you would like to pull the new image and restart the server you can add the following to docker_image.yml:

deploy:
    needs: build
    name: Deploy image on OCI compute instance
    runs-on: ubuntu-latest

    steps:
    - name: install ssh keys
      run: |
          install -m 600 -D /dev/null ~/.ssh/id_rsa
          echo "${{ secrets.SSH_PRIVATE_KEY }}" > ~/.ssh/id_rsa
          ssh-keyscan -H ${{ secrets.SSH_HOST }} > ~/.ssh/known_hosts
    - name: connect and pull
      run: ssh ubuntu@${{ secrets.SSH_HOST }} "cd ${{ secrets.WORK_DIR }} && sudo docker compose down app && sudo docker compose pull && sudo docker compose up app -d && exit"
    - name: cleanup
      run: rm -rf ~/.ssh