alpine-plus-plus

Website for our GitHub Actions and tools for developing them: https://actions.cicirello.org/

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Summary

The alpine-plus-plus Docker image is motivated by Github-actions implemented primarily with bash and shell utilities, but is also potentially applicable to any use-case where you primarily need bash and GNU tools like gawk, etc, as well as git, but also want to keep the image size relatively small. Alpine Linux is used as the base image. Alone, Alpine almost suits this purpose. However, it lacks the bash shell, and commonly used GNU tools such as findutils, gawk, etc. It also lacks git. The alpine-plus-plus image adds git, bash, findutils, coreutils, and gawk on top of Alpine Linux.

For more information, see my blog post on DEV: gnu-on-alpine and alpine-plus-plus: Two Lightweight Containers for Implementing GitHub Container Actions with Shell Scripting.

Multiplatform Image

alpine-plus-plus has the following platforms available:

• linux/386
• linux/amd64
• linux/arm/v6
• linux/arm/v7
• linux/arm64
• linux/ppc64le
• linux/s390x

Source Repository and Builds

The source repository is maintained on GitHub. The images are built on Github and pushed to Docker Hub, as well as the Github Container Registry using Github Actions.

Docker Tags and Versioning Scheme

Each image pushed to Docker Hub and the Github Container Registry is tagged as follows:

• The tag latest indicates, well, the latest image.
• Tags of the form MAJOR.MINOR.PATCH (such as 3.13.5) indicate the SemVer of the Alpine image used as the base.
• Tags of the form MAJOR.MINOR (e.g., 3.13) correspond to the most recent patch level of the Alpine image used as the base. For example, if 3.13.5 is the latest release, then 3.13 maps to this as well.
• Tags of the form MAJOR (e.g., 3) correspond to the most recent patch level of the Alpine image used as the base, with major corresponding major version. For example, if 3.13.5 is the latest release, then 3 maps to this as well.

Semantic Versioning uses version numbers of the form: MAJOR.MINOR.PATCH, where differences in MAJOR correspond to incompatible changes, differences in MINOR correspond to introduction of backwards compatible new functionality, and PATCH corresponds to backwards compatible bug fixes.

Installation and Usage

The pre-built image is hosted on both Docker Hub and the Github Container Registry. You can use it in the following ways.

Docker Pull Command

Pull the latest image from Docker Hub with the following (replace latest with a specific version number if you prefer):

docker pull cicirello/alpine-plus-plus:latest

Pull from the Github Container Registry with:

docker pull ghcr.io/cicirello/alpine-plus-plus:latest

Use as a base image in a Dockerfile

Use as a base image in a Dockerfile (replace latest with a specific version number if you prefer):

FROM cicirello/alpine-plus-plus:latest

# The rest of your Dockerfile would go here.

Or you can use as a base image (via the Github Container Registry) with:

FROM ghcr.io/cicirello/alpine-plus-plus:latest

# The rest of your Dockerfile would go here.

A specific example usage can be found in the Dockerfile of the generate-sitemap Github action.

License

Source Code License

The source code, including the Dockerfile and anything else within the Github repository for alpine-plus-plus, is licensed under the MIT License.

Image Licenses

As with all pre-built Docker images, the image itself (once built, or obtained from Docker Hub or the Github Container Registry) contains software that is covered by a variety of licenses. Since the base image is Alpine, this would include the licenses of the components of Alpine; and also includes the licenses of the GNU tools added to the image and the license for git.

If you build and distribute an image containing your software, using alpine-plus-plus as the base image, it is your responsibility to follow the licenses of all of the software contained within the image. At the time that this documentation is written, one of the effects of the combination of those licenses is a constraint on the licensing of such a pre-built image containing your software to the GPL 3.0 or later (derived from the inclusion of bash and the other GNU tools). If you desire a more permissive license for your software, one approach would be to instead distribute a Dockerfile that builds the image containing your software, rather than a pre-built image of your software, which should circumvent the issue since you would no longer be distributing a derivative of GPL licensed software.