devcontainer-helper

Original：🇺🇸 English

Translated

Use this skill when the user asks to create, configure, update, or explain a `devcontainer.json` file or development container environment.

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Sourcegabeosx/agent-skills

Added on2026-03-21

NPX Install

npx skill4agent add gabeosx/agent-skills devcontainer-helper

SKILL.md Content

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DevContainer Helper

This skill assists in creating and managing

devcontainer.json

files for consistent development environments.

Workflow

1. specific Requirements

Before generating the file, determine the user's needs:

Base Environment: Do they want a pre-built image (e.g., Ubuntu, Python, Node), a custom
```
Dockerfile
```
, or a
```
docker-compose.yml
```
setup?
Languages & Tools: What languages (Node.js, Python, Go, Rust, etc.) and tools (Git, CLI utilities) are needed?
Extensions: Are there specific VS Code extensions required?
Ports: What ports need to be forwarded?

2. Generate Configuration

Use the template in

assets/devcontainer-template.json

as a starting point.

For Image-based (Simplest): Use the

image

property. Add

features

for additional tools.

For Dockerfile: Use

build.dockerfile

property pointing to their Dockerfile.

For Docker Compose: Use

dockerComposeFile

and

service

properties.

3. Service Architecture Principles

Prefer Sidecars over In-Container Tools: For databases, caches, or message brokers, use dedicated services in
```
docker-compose.yml
```
rather than installing them via
```
Dockerfile
```
or
```
features
```
. This improves build times, resource isolation, and container startup performance.
Sidecars over Docker-in-Docker (DinD): When external services are needed for development/testing, prefer sidecar containers over DinD to reduce overhead and avoid the security complexities of privileged containers.

4. Add Features

Encourage using "Features" over manual

Dockerfile

commands for better maintainability and Dependabot support. Common features:

Node.js:
```
ghcr.io/devcontainers/features/node:1
```
(Use versioned tags like
```
version: "22"
```
to enable automated updates).
Playwright:
```
ghcr.io/devcontainers/features/playwright:1
```
(Crucial for installing OS-level browser dependencies).

pnpm:

ghcr.io/devcontainers-contrib/features/pnpm:2

.

Docker-in-Docker:

ghcr.io/devcontainers/features/docker-in-docker:2

.

Git:
```
ghcr.io/devcontainers/features/git:1
```
.

5. Performance Optimization: "Baking for Speed"

Strategy: Move global tool installations (e.g.,
```
npm install -g cli-tool
```
) from
```
postCreateCommand
```
into a custom
```
Dockerfile
```
.
Benefit: This "bakes" the tools into the image layers, making daily container startup significantly faster as these tools are cached rather than re-installed.

Implementation: Reference the

Dockerfile

in

docker-compose.yml

or

devcontainer.json

.

6. Lifecycle Scripts vs. Features

Prefer Features for language runtimes and system tools (to get automated updates).
Use Lifecycle Scripts (
```
postCreateCommand
```
) only for local project setup like
```
pnpm install
```
or database migrations.
Permissions: Use specialized features or
```
remoteUser
```
context to handle volume permission issues instead of manual
```
chown
```
in scripts where possible.

7. Automation & Dependabot

Always recommend adding
```
devcontainers
```
to
```
.github/dependabot.yml
```
when using Features. This ensures the dev environment stays up-to-date automatically.

References

See references/cheatsheet.md for a list of common

devcontainer.json

properties and valid values.