Minimal Workflow to push Docker image to Github Container Registry with Github Actions

Officially, Workflow is prepared as starter-workflows from building Docker image to pushing to Github Container Registry, but since it is doing muddy without using actions, the Workflow configuration using actions is described in this article. I will describe it.

• starter-workflows/docker-publish.yml at main · actions/starter-workflows

Premise

As for the file structure of the repository handled this time, it is assumed that the Dockerfile exists directly under the root.

-- 
|-- Dockerfile
|-- README.md
|-- .github
    |-- workflows
        |-- actions.yml
...

Solution

yml:.github/workflows/action.yml

name: Build and Publish Docker

on:
  push:
    branches:
      - master

jobs:
  build_and_push:
    runs-on: ubuntu-latest
    env:
      IMAGE_NAME: sample-app
    steps:
      - name: checkout
        uses: actions/checkout@v2

      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v1

      - name: Login to GitHub Container Registry
        uses: docker/login-action@v1
        with:
          registry: ghcr.io
          username: ${{ github.repository_owner }}
          password: ${{ secrets.CR_PAT }}

      - name: Build and push
        uses: docker/build-push-action@v2
        with:
          context: .
          push: true
          tags: |
            ghcr.io/${{ github.repository_owner }}/${{ env.IMAGE_NAME }}:latest
            ghcr.io/${{ github.repository_owner }}/${{ env.IMAGE_NAME }}:1.0.0

Workflow explanation

In this workflow, a job called build_and_push is defined. From now on, I will briefly explain what each step in the job is doing.

checkout Check out the source code. ʻActions / checkout @ v2` We are using actions.

• Checkout · Actions · GitHub Marketplace

Set up Docker Buildx The docker / build-push-action @ v2 action is doing the necessary setup for docker build here. I am using the docker / setup-buildx-action @ v1 action.

• Docker Setup Buildx · Actions · GitHub Marketplace

Login to GitHub Container Registry Do a docker login here to push the docker image to the GitHub Container Registry. Use the docker / login-action @ v1 action. Define the required parameters with with.

• Docker Login · Actions · GitHub Marketplace

• 1: Github Actions provides some environment variables by default, and this time I got them from them. Reference: Environment variables --GitHub Docs

• 2: See here for how to set the secret. Encrypted secrets - GitHub Docs

Build and push Do docker build and docker push. I am using the docker / build-push-action @ v2 action. Define the required parameters with with.

• Build and push Docker images · Actions · GitHub Marketplace

reference

• Migrating to GitHub Container Registry for Docker images - GitHub Docs