Examples

The examples/ directory in the crib repository contains working projects you can try directly:

git clone https://github.com/fgrehm/crib.git
cd crib/examples/simple
crib up && crib shell

Each example below shows the key parts of the configuration. All examples are self-contained and ready to run.

Simple (base image only)

The minimal setup: a base image, no Dockerfile, no features.

{
  "name": "simple",
  "image": "docker.io/library/debian:12-slim",
  "overrideCommand": true,
  "remoteUser": "root",
  "postCreateCommand": "echo '==> container ready'"
}

overrideCommand: true replaces the image’s default entrypoint with a long-running sleep, keeping the container alive for crib shell and crib exec.

Most of these examples use remoteUser: "root" for simplicity since the base images don’t ship a non-root user. The devcontainer base images (like the one in the Rust example) come with a vscode user preconfigured, which is what most projects use in practice.

Node.js

A Node.js project using the official Node image directly.

{
  "name": "nodejs-project",
  "image": "docker.io/library/node:22-bookworm",
  "overrideCommand": true,
  "remoteUser": "root",
  "postCreateCommand": "apt-get update && apt-get install -y git make curl"
}

Python (custom Dockerfile)

When you need to install system packages or project dependencies at build time, use a Dockerfile.

{
  "name": "python-dockerfile",
  "build": {
    "dockerfile": "Dockerfile",
    "context": "."
  },
  "overrideCommand": true,
  "remoteUser": "root"
}

# examples/python-dockerfile/.devcontainer/Dockerfile
FROM docker.io/library/python:3.12-bookworm

RUN apt-get update && apt-get install -y \
    git make curl build-essential \
    && rm -rf /var/lib/apt/lists/*

WORKDIR /workspaces/python-dockerfile

RUN pip install --no-cache-dir pytest pytest-cov black flake8

Go

{
  "name": "go-project",
  "image": "docker.io/library/golang:1.26-bookworm",
  "overrideCommand": true,
  "remoteUser": "root",
  "postCreateCommand": "apt-get update && apt-get install -y git make curl"
}

Ruby (with package cache)

Shows the package cache plugin caching bundler gems across rebuilds.

{
  "name": "ruby-project",
  "image": "docker.io/library/ruby:3.3-bookworm",
  "overrideCommand": true,
  "remoteUser": "root",
  "postCreateCommand": "bundle install"
}

cache = bundler

The bundler cache provider sets BUNDLE_PATH so gems are stored in a named Docker volume that survives rebuilds.

Rust (with cargo and apt cache)

Uses a Microsoft devcontainer base image with a non-root user and multiple cache providers.

{
  "name": "rust-project",
  "image": "mcr.microsoft.com/devcontainers/rust:1",
  "remoteUser": "vscode",
  "postCreateCommand": "sudo apt-get update && sudo apt-get install -y pkg-config libssl-dev && cargo fetch"
}

cache = cargo, apt

No overrideCommand needed here because the devcontainer base image already has a long-running entrypoint.

Docker Compose (multi-service)

A Node.js app with a Redis database, managed together by Docker Compose.

{
  "name": "compose-app",
  "dockerComposeFile": "docker-compose.yml",
  "service": "app",
  "runServices": ["app", "db"],
  "workspaceFolder": "/workspaces/${localWorkspaceFolderBasename}",
  "overrideCommand": true,
  "remoteUser": "root",
  "remoteEnv": {
    "PROJECT_NAME": "${containerEnv:PROJECT}",
    "REDIS_URL": "redis://db:6379"
  }
}

services:
  app:
    image: docker.io/library/node:20-slim
    environment:
      NODE_ENV: development
      PROJECT: ${localWorkspaceFolderBasename}
  db:
    image: docker.io/library/redis:7-alpine

Key points:

service specifies which container crib attaches to for shell, run, and exec.
runServices controls which services start on crib up.
${localWorkspaceFolderBasename} is substituted by crib before passing to compose.
${containerEnv:PROJECT} resolves against the running container’s environment.

DevContainer Features (remote)

Install tools from the devcontainer features registry without touching a Dockerfile.

{
  "name": "with-remote-features",
  "image": "docker.io/library/ubuntu:24.04",
  "features": {
    "ghcr.io/devcontainers/features/go:1": {},
    "ghcr.io/devcontainers/features/node:1": {},
    "ghcr.io/devcontainers/features/github-cli:1": {}
  },
  "overrideCommand": true,
  "remoteUser": "root"
}

Features are OCI artifacts pulled from container registries. Pass options as key-value pairs in the feature object (e.g., "version": "20" for a specific Node version).

DevContainer Features (local)

Define project-specific features as local directories.

{
  "name": "with-local-features",
  "image": "docker.io/library/ubuntu:24.04",
  "features": {
    "./features/node": {}
  },
  "overrideCommand": true,
  "remoteUser": "root"
}

Local features are referenced with ./ paths relative to the .devcontainer/ directory. Each feature needs a devcontainer-feature.json and an install.sh script. See Authoring Features for details.