This is a detailed step-by-step guide for each of the points from 1 to 8, covering the installation of Docker, creating a Docker image, setting up Docker containers, and generating OpenVPN configuration. Let's get started:

Step 1: Install Docker on Debian Server

1. Update the package repository on your Debian server:

   sudo apt update

2. Install Docker and related dependencies:

   sudo apt install docker.io

3. Start the Docker service:

   sudo systemctl start docker

4. Enable Docker to start at boot:

   sudo systemctl enable docker

Step 2: Create a Docker Image for the Development Environment

5. Create a Dockerfile for the development environment on your Debian server. Use a text editor to create a file named Dockerfile.dev:

   sudo nano Dockerfile.dev

6. Inside the Dockerfile.dev, paste the following content (customize as needed):

   FROM ubuntu:20.04
   
   # Install SSH server and necessary tools
   RUN apt-get update && \
       apt-get install -y openssh-server sudo && \
       rm -rf /var/lib/apt/lists/* && \
       mkdir /var/run/sshd
   
   # Set up a user (replace "developer" with the desired username)
   RUN useradd -m -d /home/developer -s /bin/bash developer && \
       echo 'developer:password' | chpasswd && \
       echo 'developer ALL=(ALL) NOPASSWD:ALL' >> /etc/sudoers
   
   # Expose SSH port
   EXPOSE 22
   
   CMD ["/usr/sbin/sshd", "-D"]

7. Save the Dockerfile.dev and exit the text editor.

8. Build the Docker image (replace my-dev-image with your desired image name):

   sudo docker build -t my-dev-image -f Dockerfile.dev .

Step 3: Create a Docker Container for SSH Access

9. For each user, create a Docker container based on the image you built. Replace user1-container and user1-key.pub with the desired container name and the path to the user's public SSH key:

   sudo docker run -d -p 2222:22 --name user1-container my-dev-image
   sudo docker cp /path/to/user1-key.pub user1-container:/home/developer/.ssh/authorized_keys

   Repeat this step for each user you want to grant SSH access.

Step 4: Generate OpenVPN Configuration (Optional)

10. If needed, install and configure OpenVPN on your Debian server. Refer to OpenVPN documentation for detailed instructions.

Step 5: Set Up User Access

11. Generate OpenVPN client profiles and securely distribute them to users.

12. Instruct users to install an OpenVPN client on their local machines and import their client profiles.

13. Users can connect to the OpenVPN server to establish a secure connection.

Step 6: Secure SSH Access (Optional)

14. Inside each Docker container, secure SSH access:

    • Edit the SSH configuration file /etc/ssh/sshd_config inside the container to disable password authentication (PasswordAuthentication no) and use SSH keys for authentication.

    • Restart the SSH service inside the container:

    sudo service ssh restart

Step 7: Network Configuration and Security

15. Implement firewall rules on your server to restrict access to the OpenVPN server and Docker containers' SSH ports from trusted IP addresses only. Use a tool like ufw or configure iptables as needed.

Step 8: Data Persistence (Optional)

16. To persist user data and configurations beyond the container's lifecycle, consider using Docker volumes or bind mounts. This ensures that data remains intact even if containers are recreated.

With these detailed steps, you've set up a Docker-based development environment with SSH access, addressed security concerns, and optionally added OpenVPN for secure connections. Customize the setup according to your specific requirements and security policies.