Dev Container Templates: Self Authoring Guide

This repo provides a starting point and example for creating your own custom Dev Container Templates, hosted for free on GitHub Container Registry. The example in this repository follows the Dev Container Template distribution specification.

To provide feedback on the distribution spec, please leave a comment on spec issue #71.

Repo and Template Structure

This repository contains a collection of two Templates - hello and color. These Templates serve as simple template implementations which helps containerize the project. Similar to the devcontainers/templates repo, this repository has a src folder. Each Template has its own sub-folder, containing at least a devcontainer-template.json and .devcontainer/devcontainer.json.

├── src
│   ├── color
│   │   ├── devcontainer-template.json
│   │   └──| .devcontainer
│   │      └── devcontainer.json
│   ├── hello
│   │   ├── devcontainer-template.json
│   │   └──| .devcontainer
│   │      ├── devcontainer.json
│   │      └── Dockerfile
|   ├── ...
│   │   ├── devcontainer-template.json
│   │   └──| .devcontainer
│   │      └── devcontainer.json
├── test
│   ├── color
│   │   └── test.sh
│   ├── hello
│   │   └── test.sh
│   └──test-utils
│      └── test-utils.sh
...

Options

All available options for a Template should be declared in the devcontainer-template.json. The syntax for the options property can be found in the devcontainer Template json properties reference.

For example, the color Template provides three possible options (red, gold, green), where the default value is set to "red".

{
    // ...
    "options": {
        "favorite": {
            "type": "string",
            "description": "Choose your favorite color."
            "proposals": [
                "red",
                "gold",
                "green"
            ],
            "default": "red"
        }
    }
}

An implementing tool will use the options property from the documented Dev Container Template properties for customizing the Template. See option resolution example for details.

Distributing Templates

Note: Allow GitHub Actions to create and approve pull requests should be enabled in the repository's Settings > Actions > General > Workflow permissions for auto generation of src/<template>/README.md per Template (which merges any existing src/<template>/NOTES.md).

Versioning

Templates are individually versioned by the version attribute in a Template's devcontainer-template.json. Templates are versioned according to the semver specification. More details can be found in the Dev Container Template specification.

Publishing

NOTE: The Distribution spec can be found here.

While any registry implementing the OCI Distribution spec can be used, this template will leverage GHCR (GitHub Container Registry) as the backing registry.

Templates are source files packaged together that encode configuration for a complete development environment.

This repo contains a GitHub Action workflow that will publish each template to GHCR. By default, each Template will be prefixed with the <owner/<repo> namespace. For example, the two Templates in this repository can be referenced by an implementing tool with:

ghcr.io/devcontainers/template-starter/color:latest
ghcr.io/devcontainers/template-starter/hello:latest

The provided GitHub Action will also publish a third "metadata" package with just the namespace, eg: ghcr.io/devcontainers/template-starter. This contains information useful for tools aiding in Template discovery.

'devcontainers/template-starter' is known as the template collection namespace.

Marking Template Public

For your Template to be used, it currently needs to be available publicly. By default, OCI Artifacts in GHCR are marked as private.

To make them public, navigate to the Template's "package settings" page in GHCR, and set the visibility to 'public`.

https://github.com/users/<owner>/packages/container/<repo>%2F<templateName>/settings

Adding Templates to the Index

Next you will need to add your Templates collection to our public index so that other community members can find them. Just follow these steps once per collection you create:

• Go to github.com/devcontainers/devcontainers.github.io
  • This is the GitHub repo backing the containers.dev spec site
• Open a PR to modify the collection-index.yml file

This index is from where supporting tools like VS Code Dev Containers and GitHub Codespaces surface Templates for their Dev Container Creation Configuration UI.

Testing Templates

This repo contains a GitHub Action workflow for testing the Templates. Similar to the devcontainers/templates repo, this repository has a test folder. Each Template has its own sub-folder, containing at least a test.sh.

For running the tests locally, you would need to execute the following commands -

    ./.github/actions/smoke-test/build.sh ${TEMPLATE-ID} 
    ./.github/actions/smoke-test/test.sh ${TEMPLATE-ID} 

Updating Documentation

This repo contains a GitHub Action workflow that will automatically generate documentation (ie. README.md) for each Template. This file will be auto-generated from the devcontainer-template.json and NOTES.md.