devcontainer-features

name	devcontainer-features
description	This skill should be used when the user asks about "devcontainer features", "feature installation", "installsAfter", "feature registry", "ghcr.io features", "docker-in-docker feature", "composable dev environment", "create custom feature", "publish devcontainer feature", or needs to configure the devcontainer feature system for modular environment composition.

Dev Container Feature System

Overview

Features are composable, OCI-distributed modules that add tools and capabilities to dev containers. Each feature is a self-contained package with install scripts, lifecycle commands, and metadata. Features enable building modular dev environments without monolithic Dockerfiles.

Feature Configuration

Adding Features

{
  "features": {
    "ghcr.io/devcontainers/features/docker-in-docker:2": {},
    "ghcr.io/devcontainers/features/node:1": { "version": "18" },
    "ghcr.io/devcontainers/features/python:1": { "version": "3.12" }
  }
}

Reference Format

<registry>/<namespace>/<feature>:<version>

• Registry: ghcr.io, mcr.microsoft.com, or custom OCI registry
• Namespace: Organization or user (e.g., devcontainers)
• Feature: Descriptive name (e.g., docker-in-docker, node, python)
• Version: Semver required for reproducibility (e.g., 2, 1.0, 1.0.5)

Feature Metadata (devcontainer-feature.json)

Each feature defines:

• Feature ID and version
• Lifecycle commands: onCreateCommand, postCreateCommand, postAttachCommand
• Dependencies via installsAfter
• Configuration schema for options
• Container metadata (mounts, privileged, capAdd)

Installation Order

1. Parse all features from devcontainer.json
2. Resolve installsAfter dependencies
3. Execute feature install scripts in topological order
4. Merge metadata (capabilities, mounts, env vars)
5. Final merged config passed to container creation

Common Features

Docker-in-Docker

{
  "ghcr.io/devcontainers/features/docker-in-docker:2": {},
  "mounts": [
    { "source": "dind-var-lib-docker", "target": "/var/lib/docker", "type": "volume" }
  ]
}

Language Runtimes

{
  "ghcr.io/devcontainers/features/node:1": { "version": "22" },
  "ghcr.io/devcontainers/features/python:1": { "version": "3.12" },
  "ghcr.io/devcontainers/features/rust:1": { "version": "latest" }
}

CLI Tools

{
  "ghcr.io/devcontainers/features/github-cli:1": {},
  "ghcr.io/devcontainers/features/kubectl-helm-minikube:1": {}
}

Best Practices

1. Always pin versions — Use specific semver for reproducible builds
2. Use installsAfter — Declare dependencies between features
3. Prefer official features — ghcr.io/devcontainers/features/ maintained by spec authors
4. Check feature options — Many features accept configuration (version, variant, etc.)
5. Use feature lifecycle — Features can define their own onCreateCommand/postCreateCommand
6. Volume mount caches — Pair features with named volumes for persistent caches

Feature CLI Commands

For full CLI reference, see the devcontainer-cli skill. Key feature subcommands:

devcontainer features test --workspace-folder . --features ghcr.io/org/feature:1
devcontainer features package ./src/my-feature --output-folder ./dist
devcontainer features publish ./dist --registry ghcr.io --namespace myorg
devcontainer features info ghcr.io/devcontainers/features/node:1

Additional Resources

Reference Files

For the complete feature specification and publishing workflow:

• references/feature-system.md — Full feature metadata, installation order, and publishing

Related Skills

• devcontainer-cli — Full CLI reference including feature subcommands
• devcontainer-setup — Configuring features during project setup