This repo provides a starting point and example for creating your own custom dev container Features, hosted for free on GitHub Container Registry. The example in this repository follows the dev container Feature distribution specification.
To provide feedback to the specification, please leave a comment on spec issue #70. For more broad feedback regarding dev container Features, please see spec issue #61.
This repository contains a collection of two Features - hello and color. These Features serve as simple feature implementations. Each sub-section below shows a sample devcontainer.json alongside example usage of the Feature.
Running hello inside the built container will print the greeting provided to it via its greeting option.
$ hello
Hello, user.Running color inside the built container will print your favorite color to standard out.
{
"image": "mcr.microsoft.com/devcontainers/base:ubuntu",
"features": {
"ghcr.io/devcontainers/feature-starter/color:1": {
"favorite": "green"
}
}
}$ color
my favorite color is greenSimilar to the devcontainers/features repo, this repository has a src folder. Each Feature has its own sub-folder, containing at least a devcontainer-feature.json and an entrypoint script install.sh.
├── src
│ ├── hello
│ │ ├── devcontainer-feature.json
│ │ └── install.sh
│ ├── color
│ │ ├── devcontainer-feature.json
│ │ └── install.sh
| ├── ...
│ │ ├── devcontainer-feature.json
│ │ └── install.sh
...
An implementing tool will composite the documented dev container properties from the feature's devcontainer-feature.json file, and execute in the install.sh entrypoint script in the container during build time. Implementing tools are also free to process attributes under the customizations property as desired.
All available options for a Feature should be declared in the devcontainer-feature.json. The syntax for the options property can be found in the devcontainer Feature json properties reference.
For example, the color feature provides an enum of three possible options (red, gold, green). If no option is provided in a user's devcontainer.json, the value is set to "red".
{
// ...
"options": {
"favorite": {
"type": "string",
"enum": [
"red",
"gold",
"green"
],
"default": "red",
"description": "Choose your favorite color."
}
}
}Options are exported as Feature-scoped environment variables. The option name is captialized and sanitized according to option resolution.
#!/bin/bash
echo "Activating feature 'color'"
echo "The provided favorite color is: ${FAVORITE}"
...
{ "image": "mcr.microsoft.com/devcontainers/base:ubuntu", "features": { "ghcr.io/devcontainers/feature-starter/hello:1": { "greeting": "Hello" } } }