docker-images

This repository contains docker images we use regularly, mainly in concourse pipelines.

Goals

• Build and publish images automatically based on new releases of installed software and the base operating system.
• Version all images according to the predominant software install.
• Keep images small (only install what we need).

Methodology

This approach starts with a base image, ubuntu-base, and builds by adding a single github release onto each image. By defining the base image and the single release, builds trigger automatically and cascade updates appropriately. Images also remain small.

Here is an example:

• ubuntu-cf primarily provides the Cloud Foundry CLI
• The base image is ubuntu-jq as jq is often used in conjunction with the CLI for processing json
• The ubuntu-jq base image is ubuntu-base
• The ubuntu-base base image is the Canonical supported ubuntu with curl and zip added (we use these a lot so they are good candidates for the base image).

This means a change in:

• cf will rebuild ubuntu-cf
• jq will rebuild ubuntu-jq and ubuntu-cf
• ubuntu (the base image from Canonical) will rebuild ubuntu-base, ubuntu-jq, and ubuntu-cf

To make this all work, the pipeline resources are based on github releases. We do not use apt to install things like jq as we want concourse to trigger on new github releases.

Using

If you want to set up (or extend) a similar build system for images, there are two relevant pipeline.yml definitions.

• ubuntu-base/pipeline.yml builds the base image.
• ubuntu-with-github-release/pipeline.yml builds all the other images. This is the pipeline.yml you would use to add a new image with a new github release.

By using the same ubuntu-with-github-release/pipeline.yml, you only have to define two inputs:

• config.yml contains the configuration for your image
• Dockerfile defines your image

Therefore, you can:

• create a directory for your image: ubuntu-<some-release>
• define a config.yml
• add your Dockerfile

You can then create a pipeline for your image with something like:

fly -t $target sp -p ubuntu-<some-release> -c ${this_directory}/ubuntu-with-github-release/pipeline.yml -l ${this_directory}/ubuntu-<some-release>/config.yml 

You can also look at set-pipelines.sh if you want to take the approach of being able to quickly recreate pipelines.