LinuxInstalls/ssh/README.md

Multi-Instance SSH Server Generator

A lightweight Bash script that automatically creates, configures, and manages completely isolated OpenSSH server instances on Linux.

Perfect for providing dedicated SSH access to specific teams, contractors, or applications without touching your primary server's SSH configuration.

Features

• Complete Isolation: Each instance gets its own configuration directory (/opt/custom_sshd/<name>) and independent host keys.
• Auto-Port Assignment: Automatically scans for the next available port starting from 2222 to prevent collisions.
• Systemd Integration: Generates a dedicated systemd service for each instance so they start on boot and auto-restart if they crash.
• Auto-Firewall: Detects your active firewall (ufw, firewalld, or iptables) and automatically opens the required TCP port.

Prerequisites

• A Linux distribution using systemd
• Root privileges (sudo)
• sshd (OpenSSH Server) installed

Usage

1. Make the script executable:

   chmod +x create_ssh_service.sh

2. Create a new SSH instance: Pass the desired name of your instance as the only argument.

sudo ./create_ssh_service.sh dev_team

3. Connect to your new instance: The script will output the assigned port (e.g., 2222). Use it to connect:

ssh -p 2222 username@your-server-ip

Management & Maintenance

Every instance runs as its own systemd service named custom-sshd-<instance_name>.service.

Check status:

sudo systemctl status custom-sshd-dev_team.service

View live logs:

sudo journalctl -u custom-sshd-dev_team.service -f

Restart the instance:

sudo systemctl restart custom-sshd-dev_team.service

Completely remove an instance:

sudo systemctl disable --now custom-sshd-dev_team.service
sudo rm /etc/systemd/system/custom-sshd-dev_team.service
sudo rm -rf /opt/custom_sshd/dev_team
sudo systemctl daemon-reload

Note: If you uninstall, you will need to manually remove the port rule from your firewall.