Add multiarch support

[ndanyluk]

Hi, sorry this is one of my first PRs and I'm not sure if this is the right format or not. Please let me know and I can adjust or delete this as needed.

This PR adds support for docker manifest lists and uses travis-ci to automate build and deployment of your lightweight docker base image. I did not modify the content of the image with the exception of adding the qemu static binary for the desired architecture to allow for building with travis-ci (which only uses x86 machines).

There are now multiple Dockerfiles (and the Makefile has been adjusted) to allow for cross-building on multiple architectures (the default light-baseimage appears to be built on x86 and thus cannot be used on armv7 or arm64 devices like the Raspberry Pi).

The Makefile now creates repositories named light-baseimage-ARCH. These images have had qemu static binaries added so they can be built from the arm64v8 and arm32v7 variants of debian stretch slim.

Additionally, since I use Travis-CI for my own images, I added support for it here. This automates building/deploying of the images and does a quick test to make sure the image runs after build (without exec format errors). I have tested this in my own repo (ndanyluk/light-baseimage) and the builds pass.

The multi-stage Travis-CI build creates the new repositories in parallel, then makes use of the Docker Manifest command (experimental) to create a single multi-arch image (arm32, arm64, and amd64) and deploy to Docker Hub.

[BertrandGouny]

Thanks a lot for your contribution ! This is very welcomed :)
Merged in branch release-1.2.0

[ndanyluk]

Thanks, happy to contribute! Oh I should also mention that the Dockerfiles are updated to add QEMU but the binaries are not included in the repo so a regular build will fail. Travis downloads them during build since that's how I build all my images usually.

You can find the QEMU static binary project I pulled from here https://github.com/multiarch/qemu-user-static

Hope this all helps and let me know if I need to change anything :)

[anagno]

Hello Everyone,

Out of curiosity. Is there a specific reason that the old bats was preferred and not the new repository (https://github.com/bats-core/bats-core)? Apparently the sstephenson/bats is abandoned (sstephenson/bats#248) and a new community has already emerge (sstephenson/bats#150).

Also I would pin the checkout to a specific version/release, so you are certain that something is broken in your build and not in your build scripts :)

KR,

Vasileios

Update: Nevermind. I saw that in the documentation of the image we are also using the old version.

[vk496]

Thanks a lot for your work! Hope this PR will be merged soon and applied in other containers for arm support (like openldap) 😃

[blaggacao]

This can be simplified a lot with docker buildx: https://www.docker.com/blog/multi-arch-build-and-images-the-simple-way/