Docker Image Build Github Action

This Github action builds a Docker image based on a given Git tag reference. The Git tag must start with a "v" prefix, for example "v1.23.4+5"

It's also possible to provide a script which can dynamically set environment variables which are then used as build arguments. That way you can retrieve a version number of a specific dependency via a web service or URL and pass the information to your Dockerfile.

Example workflow

name: Build and release Docker images
on:
  push:
    branches-ignore:
      - '**'
    tags:
      - 'v*.*.*'

jobs:
  build:
    runs-on: ubuntu-latest
    steps:

      - uses: actions/checkout@v2
        with:
          fetch-depth: 1

      - name: Build Docker image
        uses: flownative/action-docker-build@v1
        with:
          tag_ref: ${{ github.ref }}
          image_name: flownative/docker-base/base
          registry_password: ${{ secrets.GITHUB_TOKEN }}

Inputs

The following inputs are used by this action:

• tag_ref: The full Git tag reference. This must be a semver tag ref of an existing tagged image. For example, refs/tags/v1.2.5+12
• git_sha: The SHA hash of the Git commit being used for the build. If set, this value is used as a label for the resulting Docker image
• git_repository_url: The URL leading to the Git repository. If set, this value is used as a label for the resulting Docker image
• image_name: The image name to build, without tag. For example, flownative/docker-magic-image/magic-image
• image_tag: The image tag to build. If empty, the tag is derived from tag_ref: e.g. v1.2.5
• registry_password: Password / token for the Github Docker image registry

Outputs

After a successful run, the action provides your workflow with the following outputs:

• image_name: The name of the Docker image, which was built and pushed
• image_tag: The tag of the Docker image, which was built and pushed
• git_tag: The tag of the Git commit, which was discovered during the process

Docker image labels

This action automatically sets a couple of labels in the built Docker image. This metadata may help you and others identifying the state of source code used at build time.

The following labels are set:

• org.label-schema.version: set to the image tag
• org.label-schema.build-date: set to the current date and time during the build
• org.label-schema.vcs-url: set to to the Git repository URL
• org.label-schema.vcs-ref: set to the SHA of the current Git commit

Hint: You can review the image labels by running docker inspect.

Dynamic build arguments

If the following file is present as .github/workflows/build-env.sh, its exported environment environment variables (you can provide multiple ones) will be parsed ...

BUILD_ARG_MICRO_VERSION=$(wget -qO- https://versions.flownative.io/projects/base/channels/stable/versions/micro.txt)
export BUILD_ARG_MICRO_VERSION

... and can be used in a Dockerfile as build arguments as such:

…
ARG MICRO_VERSION
ENV MICRO_VERSION=${MICRO_VERSION}
RUN wget --no-hsts https://github.com/zyedidia/micro/releases/download/v${MICRO_VERSION}/micro-${MICRO_VERSION}-linux64.tar.gz; \
    tar xfz micro-${MICRO_VERSION}-linux64.tar.gz; \
    mv micro-${MICRO_VERSION}/micro /usr/local/bin; \
    chmod 755 /usr/local/bin/micro; \
    rm -rf micro-${MICRO_VERSION}* /var/log/* /var/lib/dpkg/status-old
…

Implementation Note

The repository of this action does not contain the actual implementation code. Instead, it's referring to a pre-built image in its Dockerfile in order to save resources and speed up workflow runs.

The code of this action can be found here.