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a task for building Docker images without a Docker daemon
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A Concourse task to builds Docker images without pushing and without spinning up a Docker daemon. Currently uses img for the building and saving.

This repository describes an image which should be used to run a task similar to example.yml.

A stretch goal of this is to support running without privileged: true, though it currently still requires it.

task config

Concourse doesn't yet have easily distributable task configs (there's an open call for an RFC), so we'll just have to document what you need to set here.


The task's image should refer to concourse/builder. You can either configure this via image_resource or pull it in as part of your pipeline.


The following params are required:

  • $REPOSITORY: the repository to name the image, e.g. concourse/builder.

The following are optional:

  • $TAG (default latest): the tag to apply to the image.

  • $CONTEXT (default .): the path to the directory to build. This should refer to one of the inputs.

  • $DOCKERFILE (default $CONTEXT/Dockerfile): the path to the Dockerfile to build.


There are no required inputs - your task should just list each artifact it needs as an input.


Your task may configure an output called image. The saved image tarball will be written to image.tar within the output. This tarball can be passed along to docker load, or uploaded to a registry using the Registry Image resource.


Build caching can be enabled by configuring a cache named cache on the task.


Your task should execute the build script.


This repo contains an example.yml, which builds the image for the builder itself:

fly -t dev execute -c example.yml -o image=. -p
docker load -i image.tar
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