Most of our CI Jobs running on Nomad are containerized via Docker to ensure reproducibility between builds.

The docker image definitions are available in alisw/docks, and the CERN docker registry is https://registry.cern.ch/

Rebuilding a Docker image

If an image definition has changed, it must be rebuilt and pushed to the proper registry for Nomad to use it in new job allocations.

Packer-defined images

Newer images have a packer.json file, which allows them to be built using Hashicorp packer. This has the nice advantage that we can customize and upload the images in one go.

There's a GitHub Action here that will rebuild and push the images for you.

In case you prefer to do it manually:

brew install packer # > 0.10.0
cd <image-name>
packer build packer.json

If you don't want to upload the finished image to DockerHub (e.g. if you're just testing changes to the image, or you don't have the rights to upload), remove the "docker-push" entry from "post-processors" in the packer.json you're using. (JSON doesn't allow trailing commas in arrays, so don't forget to remove the comma as well!)

Dockerfile-defined images

Older images without a packer.json can be built with:

docker build -t alisw/<image-name> <image-name>

Conventions

The CI uses an image named -builder where is the architecture of the image. The CI system will automatically select the correct image for a given architecture, so the image name must match the format exactly.

https://github.com/alisw/ci-jobs/blob/master/ci/ci.nomad