About

GitHub Action to build and push Docker images with Buildx with full support of the features provided by Moby BuildKit builder toolkit. This includes multi-platform build, secrets, remote cache, etc. and different builder deployment/namespacing options.

---

• Usage
  • Git context
  • Path context
• Examples
• Customizing
  • inputs
  • outputs
• Troubleshooting
• Contributing

Usage

In the examples below we are also using 3 other actions:

• setup-buildx action will create and boot a builder using by default the docker-container driver. This is not required but recommended using it to be able to build multi-platform images, export cache, etc.
• setup-qemu action can be useful if you want to add emulation support with QEMU to be able to build against more platforms.
• login action will take care to log in against a Docker registry.

Git context

By default, this action uses the Git context, so you don't need to use the actions/checkout action to check out the repository as this will be done directly by BuildKit.

The git reference will be based on the event that triggered your workflow and will result in the following context: https://github.com/<owner>/<repo>.git#<ref>.

name: ci

on:
  push:
    branches:
      - 'main'

jobs:
  docker:
    runs-on: ubuntu-latest
    steps:
      -
        name: Set up QEMU
        uses: docker/setup-qemu-action@v2
      -
        name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v2
      -
        name: Login to Docker Hub
        uses: docker/login-action@v2
        with:
          username: ${{ secrets.DOCKERHUB_USERNAME }}
          password: ${{ secrets.DOCKERHUB_TOKEN }}
      -
        name: Build and push
        uses: docker/build-push-action@v4
        with:
          push: true
          tags: user/app:latest

Be careful because any file mutation in the steps that precede the build step will be ignored, including processing of the .dockerignore file since the context is based on the Git reference. However, you can use the Path context using the context input alongside the actions/checkout action to remove this restriction.

Default Git context can also be provided using the Handlebars template expression {{defaultContext}}. Here we can use it to provide a subdirectory to the default Git context:

      -
        # Setting up Docker Buildx with docker-container driver is required
        # at the moment to be able to use a subdirectory with Git context
        name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v2
      -
        name: Build and push
        uses: docker/build-push-action@v4
        with:
          context: "{{defaultContext}}:mysubdir"
          push: true
          tags: user/app:latest

Warning

Subdirectory for Git context is available from BuildKit v0.9.0. If you're using the docker builder (default if setup-buildx-action not used), then BuildKit in Docker Engine will be used. As Docker Engine < v22.x.x embeds Buildkit 0.8.2 at the moment, it does not support this feature. It's therefore required to use the setup-buildx-action at the moment.

Building from the current repository automatically uses the GitHub Token, so it does not need to be passed. If you want to authenticate against another private repository, you have to use a secret named GIT_AUTH_TOKEN to be able to authenticate against it with Buildx:

      -
        name: Build and push
        uses: docker/build-push-action@v4
        with:
          push: true
          tags: user/app:latest
          secrets: |
            GIT_AUTH_TOKEN=${{ secrets.MYTOKEN }}            

Path context

name: ci

on:
  push:
    branches:
      - 'main'

jobs:
  docker:
    runs-on: ubuntu-latest
    steps:
      -
        name: Checkout
        uses: actions/checkout@v3
      -
        name: Set up QEMU
        uses: docker/setup-qemu-action@v2
      -
        name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v2
      -
        name: Login to Docker Hub
        uses: docker/login-action@v2
        with:
          username: ${{ secrets.DOCKERHUB_USERNAME }}
          password: ${{ secrets.DOCKERHUB_TOKEN }}
      -
        name: Build and push
        uses: docker/build-push-action@v4
        with:
          context: .
          push: true
          tags: user/app:latest

Examples

See https://docs.docker.com/build/ci/github-actions/examples/.

Customizing

inputs

Following inputs can be used as step.with keys

List type is a newline-delimited string

cache-from: |
  user/app:cache
  type=local,src=path/to/dir  

CSV type is a comma-delimited string

tags: name/app:latest,name/app:1.0.0

Name	Type	Description
add-hosts	List/CSV	List of customs host-to-IP mapping (e.g., docker:10.180.0.1)
allow	List/CSV	List of extra privileged entitlement (e.g., network.host,security.insecure)
attests	List	List of attestation parameters (e.g., type=sbom,generator=image)
builder	String	Builder instance (see setup-buildx action)
build-args	List	List of build-time variables
build-contexts	List	List of additional build contexts (e.g., name=path)
cache-from	List	List of external cache sources (e.g., type=local,src=path/to/dir)
cache-to	List	List of cache export destinations (e.g., type=local,dest=path/to/dir)
cgroup-parent	String	Optional parent cgroup for the container used in the build
context	String	Build's context is the set of files located in the specified PATH or URL (default Git context)
file	String	Path to the Dockerfile. (default {context}/Dockerfile)
labels	List	List of metadata for an image
load	Bool	Load is a shorthand for --output=type=docker (default false)
network	String	Set the networking mode for the RUN instructions during build
no-cache	Bool	Do not use cache when building the image (default false)
no-cache-filters	List/CSV	Do not cache specified stages
outputs¹	List	List of output destinations (format: type=local,dest=path)
platforms	List/CSV	List of target platforms for build
provenance	Bool/String	Generate provenance attestation for the build (shorthand for --attest=type=provenance)
pull	Bool	Always attempt to pull all referenced images (default false)
push	Bool	Push is a shorthand for --output=type=registry (default false)
sbom	Bool/String	Generate SBOM attestation for the build (shorthand for --attest=type=sbom)
secrets	List	List of secrets to expose to the build (e.g., key=string, GIT_AUTH_TOKEN=mytoken)
secret-files	List	List of secret files to expose to the build (e.g., key=filename, MY_SECRET=./secret.txt)
shm-size	String	Size of /dev/shm (e.g., 2g)
ssh	List	List of SSH agent socket or keys to expose to the build
tags	List/CSV	List of tags
target	String	Sets the target stage to build
ulimit	List	Ulimit options (e.g., nofile=1024:1024)
github-token	String	GitHub Token used to authenticate against a repository for Git context (default ${{ github.token }})

Note

• ¹ multiple outputs are not yet supported

outputs

Following outputs are available

Name	Type	Description
imageid	String	Image ID
digest	String	Image digest
metadata	JSON	Build result metadata

Troubleshooting

See TROUBLESHOOTING.md

Contributing

Want to contribute? Awesome! You can find information about contributing to this project in the CONTRIBUTING.md