DevShell - Ubuntu 24.04 Development Container

A clean, isolated Ubuntu 24.04 development environment with SSH access, Docker CLI, and Docker Compose v2 integration for Synology NAS.

Features

• Ubuntu 24.04 LTS base image
• SSH-only authentication (no passwords)
• Docker CLI + Compose v2 with host socket passthrough
• User identity mirroring (UID/GID matching Synology user)
• GitHub Actions CI/CD for automated builds
• GHCR image distribution (no local builds needed)

Architecture

The devshell runs on your Synology NAS but is built externally via GitHub Actions to avoid CPU/resource constraints on the DS220+.

Build & Deployment Flow

GitHub Push → Actions Build → GHCR Push → NAS Pull → Container Start

Prerequisites

On GitHub

1. Fork or create this repository
2. Enable GitHub Actions
3. GitHub Container Registry is automatically available with GITHUB_TOKEN

On Synology NAS

1. Get Docker socket GID:

   stat -c %g /var/run/docker.sock

2. Create SSH keys directory:

   mkdir -p /volume1/docker/stacks/devshell/ssh

3. Add your public SSH key:

   cat ~/.ssh/id_ed25519.pub >> /volume1/docker/stacks/devshell/ssh/authorized_keys
   chmod 600 /volume1/docker/stacks/devshell/ssh/authorized_keys

Deployment on NAS

1. Create Stack Directory

ssh msn0624c@ngaged.synology.me -p 54321
cd /volume1/docker/stacks
mkdir -p devshell/ssh
cd devshell

2. Copy docker-compose.yml

Use the provided docker-compose.yml file from this repository.

3. Create .env File

nano .env

Add:

USERNAME=msn0624c
USER_UID=1026
USER_GID=100
ADMIN_GID=101
DOCKER_GID=999  # Use the value from stat command above
GITHUB_USERNAME=YOUR_GITHUB_USERNAME

4. Deploy

# Pull latest image from GHCR
docker compose pull

# Start container
docker compose up -d

# Check logs
docker compose logs -f

DNS Configuration

Set up DNS record for external access:

• Type: A record
• Name: devshell.nsystems.live
• Value: Your WAN IP
• Proxy: OFF (DNS only)

Router Configuration

Forward external port 22 to NAS internal port 2222:

• External: Port 22
• Internal: Port 2222 → 192.168.0.164

Access Methods

External (Public)

ssh msn0624c@devshell.nsystems.live

Internal (LAN)

ssh -p 2222 msn0624c@192.168.0.164

VS Code Remote-SSH

Add to ~/.ssh/config:

Host devshell
  HostName devshell.nsystems.live
  User msn0624c
  Port 22

Host devshell-lan
  HostName 192.168.0.164
  User msn0624c
  Port 2222

Updating

When you push changes to the GitHub repository:

1. GitHub Actions automatically builds new image
2. Image is pushed to GHCR with :latest and :sha-xxxxx tags
3. On NAS, pull and restart:

cd /volume1/docker/stacks/devshell
docker compose pull
docker compose up -d

Troubleshooting

Check container logs

docker compose logs devshell

Verify Docker socket access

docker exec devshell docker ps

Check SSH configuration

docker exec devshell cat /etc/ssh/sshd_config

Verify user permissions

docker exec devshell id msn0624c
docker exec devshell groups msn0624c

Test SSH key

docker exec devshell ls -la /home/msn0624c/.ssh/

Security Notes

• No password authentication - SSH keys only
• No root login - Root SSH access disabled
• Passwordless sudo - User has sudo without password (trust-based)
• Docker socket access - User can control host Docker (intentional for dev environment)

Directory Structure

devshell/
├── .github/
│   └── workflows/
│       └── build-and-push.yml    # CI/CD workflow
├── Dockerfile                     # Container image definition
├── entrypoint.sh                  # Runtime configuration script
├── docker-compose.yml             # NAS deployment configuration
├── .env.example                   # Environment variables template
└── README.md                      # This file

# On NAS:
/volume1/docker/stacks/devshell/
├── docker-compose.yml
├── .env
└── ssh/
    └── authorized_keys            # Your SSH public keys

License

MIT