GitHub Codespaces

Cloud development environments that work anywhere.

Prerequisites

• GitHub Account: With Codespaces access
• gh CLI: Install from https://cli.github.com/
• Authentication: Run gh auth login

Quick Reference

Core Commands

Action	Command
Create codespace	gh codespace create -r owner/repo
List codespaces	gh codespace list
Open in VS Code	gh codespace code -c <name>
Open in browser	gh codespace view -c <name> -w
SSH into codespace	gh codespace ssh -c <name>
Stop codespace	gh codespace stop -c <name>
Delete codespace	gh codespace delete -c <name>

Machine Types

Type	vCPUs	RAM	Storage	Best For
Basic	2	8GB	32GB	Simple projects, docs
Standard	4	16GB	32GB	Most development
Large	8	32GB	64GB	Full-stack, multiple services
XL	16	64GB	128GB	Data science, ML
GPU	4+	16GB+	64GB+	ML training, CUDA

DevContainer Configuration

Directory Structure

.devcontainer/
+-- devcontainer.json           # Default configuration
+-- web-frontend/
|   +-- devcontainer.json       # Frontend-specific
+-- backend-api/
|   +-- devcontainer.json       # Backend-specific
+-- data-science/
    +-- devcontainer.json       # Data science config

Basic devcontainer.json

{
  "name": "Project Dev Environment",
  "image": "mcr.microsoft.com/devcontainers/universal:2",
  "features": {
    "ghcr.io/devcontainers/features/node:1": {},
    "ghcr.io/devcontainers/features/python:1": {}
  },
  "customizations": {
    "vscode": {
      "extensions": [
        "GitHub.copilot",
        "ms-python.python"
      ]
    }
  },
  "postCreateCommand": "npm install",
  "forwardPorts": [3000, 5000]
}

Lifecycle Scripts

postCreateCommand

Runs once when container is created:

"postCreateCommand": "npm install && npm run setup"

postStartCommand

Runs every time codespace starts:

"postStartCommand": "npm run dev:services"

postAttachCommand

Runs when VS Code attaches:

"postAttachCommand": "echo 'Welcome! Run npm start to begin.'"

Secrets Management

Setting Secrets

# For a specific repo
gh secret set API_KEY --repo owner/repo

# For Codespaces specifically
gh secret set DB_PASSWORD --app codespaces

# For user (all Codespaces)
gh secret set NPM_TOKEN --user

Using Secrets in devcontainer.json

{
  "containerEnv": {
    "DATABASE_URL": "${localEnv:DATABASE_URL}"
  },
  "secrets": {
    "API_KEY": {
      "description": "API key for external service"
    }
  }
}

Port Forwarding

Automatic Forwarding

{
  "forwardPorts": [3000, 5000, 8080],
  "portsAttributes": {
    "3000": {
      "label": "Frontend",
      "onAutoForward": "openBrowser"
    },
    "5000": {
      "label": "API",
      "onAutoForward": "notify"
    }
  }
}

Manual Forwarding

gh codespace ports forward 3000:3000 -c <codespace-name>

Common Workflows

Quick Start New Feature

# Create codespace for feature branch
gh codespace create -r owner/repo -b feature-branch -m standardLinux

# Open in VS Code
gh codespace code

PR Review in Codespace

# Create codespace from PR
gh codespace create -r owner/repo --branch pr-branch

# Or use the PR directly
gh pr checkout 123
gh codespace create

Share Environment

# Export port with visibility
gh codespace ports visibility 3000:public -c <name>

# Get shareable URL
gh codespace ports -c <name>

Performance Optimization

Prebuilds

Enable prebuilds for faster startup:

// .github/codespaces/prebuild.json
{
  "triggers": {
    "branches": ["main", "develop"],
    "paths": ["package.json", ".devcontainer/**"]
  }
}

Dotfiles Repository

Configure personal dotfiles in GitHub Settings > Codespaces.

Cost Management

Auto-stop Settings

Configure in GitHub Settings > Codespaces:

• Default idle timeout: 30 minutes
• Retention period: 7 days

Best Practices

1. Stop when not in use: gh codespace stop
2. Delete completed work: gh codespace delete
3. Use appropriate machine size: Don't over-provision
4. Enable prebuilds: Faster startup, less billing

Troubleshooting

Issue	Solution
Slow startup	Enable prebuilds
Out of storage	Delete unused files, increase disk
Extension not working	Check devcontainer extensions config
Port not accessible	Check forwardPorts configuration
Environment variables missing	Verify secrets are set

When to Use This Skill

• Setting up cloud development environments
• Configuring devcontainers for team consistency
• Managing Codespaces via CLI
• Optimizing development environment performance
• Sharing development environments
• PR reviews in isolated environments