Publishing Docker images

Introduction

This guide shows you how to create a workflow that performs a Docker build, and then publishes Docker images to Docker Hub or GitHub Packages. With a single workflow, you can publish images to a single registry or to multiple registries.

Prerequisites

We recommend that you have a basic understanding of workflow configuration options and how to create a workflow file. For more information, see "Learn GitHub Actions."

You might also find it helpful to have a basic understanding of the following:

• "Encrypted secrets"
• "Authentication in a workflow"
• "Working with the Docker registry"

About image configuration

This guide assumes that you have a complete definition for a Docker image stored in a GitHub repository. For example, your repository must contain a Dockerfile, and any other files needed to perform a Docker build to create an image.

In this guide, we will use the Docker build-push-action action to build the Docker image and push it to one or more Docker registries. For more information, see build-push-action.

Publishing images to Docker Hub

Each time you create a new release on GitHub Enterprise Server, you can trigger a workflow to publish your image. The workflow in the example below runs when the release event triggers with the created activity type. For more information on the release event, see "Events that trigger workflows."

In the example workflow below, we use the Docker login-action and build-push-action actions to build the Docker image and, if the build succeeds, push the built image to Docker Hub.

To push to Docker Hub, you will need to have a Docker Hub account, and have a Docker Hub repository created. For more information, see "Pushing a Docker container image to Docker Hub" in the Docker documentation.

The login-action options required for Docker Hub are:

• username and password: This is your Docker Hub username and password. We recommend storing your Docker Hub username and password as secrets so they aren't exposed in your workflow file. For more information, see "Creating and using encrypted secrets."

The metadata-action option required for Docker Hub is:

• images: The namespace and name for the Docker image you are building/pushing to Docker Hub.

The build-push-action options required for Docker Hub are:

• tags: The tag of your new image in the format DOCKER-HUB-NAMESPACE/DOCKER-HUB-REPOSITORY:VERSION. You can set a single tag as shown below, or specify multiple tags in a list.
• push: If set to true, the image will be pushed to the registry if it is built successfully.

# This workflow uses actions that are not certified by GitHub.
# They are provided by a third-party and are governed by
# separate terms of service, privacy policy, and support
# documentation.

# GitHub recommends pinning actions to a commit SHA.
# To get a newer version, you will need to update the SHA.
# You can also reference a tag or branch, but the action may change without warning.

name: Publish Docker image

on:
  release:
    types: [published]

jobs:
  push_to_registry:
    name: Push Docker image to Docker Hub
    runs-on: [self-hosted]
    steps:
      - name: Check out the repo
        uses: actions/checkout@v2
      
      - name: Log in to Docker Hub
        uses: docker/login-action@f054a8b539a109f9f41c372932f1ae047eff08c9
        with:
          username: ${{ secrets.DOCKER_USERNAME }}
          password: ${{ secrets.DOCKER_PASSWORD }}
      
      - name: Extract metadata (tags, labels) for Docker
        id: meta
        uses: docker/metadata-action@98669ae865ea3cffbcbaa878cf57c20bbf1c6c38
        with:
          images: my-docker-hub-namespace/my-docker-hub-repository
      
      - name: Build and push Docker image
        uses: docker/build-push-action@ad44023a93711e3deb337508980b4b5e9bcdc5dc
        with:
          context: .
          push: true
          tags: ${{ steps.meta.outputs.tags }}
          labels: ${{ steps.meta.outputs.labels }}

The above workflow checks out the GitHub repository, uses the login-action to log in to the registry, and then uses the build-push-action action to: build a Docker image based on your repository's Dockerfile; push the image to Docker Hub, and apply a tag to the image.

Publishing images to GitHub Packages

Each time you create a new release on GitHub Enterprise Server, you can trigger a workflow to publish your image. The workflow in the example below runs when the release event triggers with the created activity type. For more information on the release event, see "Events that trigger workflows."

In the example workflow below, we use the Docker login-action and build-push-action actions to build the Docker image, and if the build succeeds, push the built image to GitHub Packages.

The login-action options required for GitHub Packages are:

• registry: Must be set to docker.pkg.github.com.
• username: You can use the ${{ github.actor }} context to automatically use the username of the user that triggered the workflow run. For more information, see "Contexts."
• password: You can use the automatically-generated GITHUB_TOKEN secret for the password. For more information, see "Authenticating with the GITHUB_TOKEN."

The build-push-action options required for GitHub Packages are:

• push: If set to true, the image will be pushed to the registry if it is built successfully.

• tags: Must be set in the format docker.pkg.github.com/OWNER/REPOSITORY/IMAGE_NAME:VERSION.

  For example, for an image named octo-image stored on GitHub at http://github.com/octo-org/octo-repo, the tags option should be set to docker.pkg.github.com/octo-org/octo-repo/octo-image:latest. You can set a single tag as shown below, or specify multiple tags in a list.

# This workflow uses actions that are not certified by GitHub.
# They are provided by a third-party and are governed by
# separate terms of service, privacy policy, and support
# documentation.

# GitHub recommends pinning actions to a commit SHA.
# To get a newer version, you will need to update the SHA.
# You can also reference a tag or branch, but the action may change without warning.

name: Publish Docker image

on:
  release:
    types: [published]
jobs:
  push_to_registry:
    name: Push Docker image to GitHub Packages
    runs-on: ubuntu-latest
    permissions:
      packages: write
      contents: read
    steps:
      - name: Check out the repo
        uses: actions/checkout@v2
      
      - name: Log in to GitHub Docker Registry
        uses: docker/login-action@f054a8b539a109f9f41c372932f1ae047eff08c9
        with:
          registry: docker.pkg.github.com
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}
      
      - name: Build and push Docker image
        uses: docker/build-push-action@ad44023a93711e3deb337508980b4b5e9bcdc5dc
        with:
          context: .
          push: true
          tags: |
            docker.pkg.github.com/${{ github.repository }}/octo-image:${{ github.sha }}
            docker.pkg.github.com/${{ github.repository }}/octo-image:${{ github.event.release.tag_name }}

The above workflow checks out the GitHub Enterprise Server repository, uses the login-action to log in to the registry, and then uses the build-push-action action to: build a Docker image based on your repository's Dockerfile; push the image to the Docker registry, and apply the commit SHA and release version as image tags.

Publishing images to Docker Hub and GitHub Packages

In a single workflow, you can publish your Docker image to multiple registries by using the login-action and build-push-action actions for each registry.

The following example workflow uses the steps from the previous sections ("Publishing images to Docker Hub" and "Publishing images to GitHub Packages") to create a single workflow that pushes to both registries.

# This workflow uses actions that are not certified by GitHub.
# They are provided by a third-party and are governed by
# separate terms of service, privacy policy, and support
# documentation.

# GitHub recommends pinning actions to a commit SHA.
# To get a newer version, you will need to update the SHA.
# You can also reference a tag or branch, but the action may change without warning.

name: Publish Docker image

on:
  release:
    types: [published]

jobs:
  push_to_registries:
    name: Push Docker image to multiple registries
    runs-on: [self-hosted]
    permissions:
      packages: write
      contents: read
    steps:
      - name: Check out the repo
        uses: actions/checkout@v2
      
      - name: Log in to Docker Hub
        uses: docker/login-action@f054a8b539a109f9f41c372932f1ae047eff08c9
        with:
          username: ${{ secrets.DOCKER_USERNAME }}
          password: ${{ secrets.DOCKER_PASSWORD }}
      
      - name: Log in to the Docker registry
        uses: docker/login-action@f054a8b539a109f9f41c372932f1ae047eff08c9
        with:
          registry: docker.pkg.github.com
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}
      
      - name: Extract metadata (tags, labels) for Docker
        id: meta
        uses: docker/metadata-action@98669ae865ea3cffbcbaa878cf57c20bbf1c6c38
        with:
          images: |
            my-docker-hub-namespace/my-docker-hub-repository
            docker.pkg.github.com/${{ github.repository }}/my-image
      
      - name: Build and push Docker images
        uses: docker/build-push-action@ad44023a93711e3deb337508980b4b5e9bcdc5dc
        with:
          context: .
          push: true
          tags: ${{ steps.meta.outputs.tags }}
          labels: ${{ steps.meta.outputs.labels }}

The above workflow checks out the GitHub Enterprise Server repository, uses the login-action twice to log in to both registries and generates tags and labels with the metadata-action action. Then the build-push-action action builds and pushes the Docker image to Docker Hub and the Docker registry.