VPN Status Monitor with systemd and tmux

This project sets up a script that monitors VPN connection status, displays it in the tmux status bar, and updates dynamically using systemd timers. The goal is to provide a lightweight, efficient solution for monitoring VPN connections in real-time using tmux.

Prerequisites

• tmux installed and configured
• systemd available on your system (most Linux distributions include this by default)
• Basic shell scripting knowledge

Step-by-Step Setup

1. Create the VPN Status Script

1. Create the Bash script that checks the VPN status. We'll monitor the tun0 interface (adjust as needed).

   Save the following script as vpn_status.sh under /home/$USER/:

   #!/bin/bash
   
   # Path to store VPN status output
   STATUS_FILE="$HOME/vpn_status_output.txt"
   
   # Function to update VPN status in tmux
   update_tmux_for_vpn_connected() {
       local vpn_ip=$1
       echo "$vpn_ip" > "$STATUS_FILE"  # Write IP to the status file
       tmux refresh-client -S           # Refresh tmux to show updated status
   }
   
   # Function to update tmux for VPN disconnected
   update_tmux_for_vpn_disconnected() {
       echo "Disconnected" > "$STATUS_FILE"  # Write "Disconnected" to the status file
       tmux refresh-client -S                # Refresh tmux
   }
   
   # Check VPN status and get IP address
   ip=$(/usr/sbin/ifconfig tun0 2>/dev/null | grep 'inet ' | awk '{print $2}')
   if [ -n "$ip" ]; then
       update_tmux_for_vpn_connected "$ip"
   else
       update_tmux_for_vpn_disconnected
   fi

2. Make the script executable:

   chmod +x /home/$USER/vpn_status.sh

2. Configure tmux to Display VPN Status

1. Edit your tmux configuration file (~/.tmux.conf) and add the following line to display the VPN status:

   set -g status-right "VPN: #(cat /home/$USER/vpn_status_output.txt) | #(whoami)@#(hostname -s)"

2. Reload tmux:

   tmux source ~/.tmux.conf

3. Create the systemd Service

1. Create a new systemd service file at /etc/systemd/system/vpn-status.service:

   [Unit]
   Description=VPN Status Monitor Service
   
   [Service]
   ExecStart=/bin/bash /home/%i/vpn_status.sh
   WorkingDirectory=/home/%i
   User=%i
   StandardOutput=journal
   StandardError=journal
   
   [Install]
   WantedBy=multi-user.target

4. Create the systemd Timer

1. Create a timer file at /etc/systemd/system/vpn-status.timer to run the service every 5 seconds:

   [Unit]
   Description=Run VPN Status Monitor every 5 seconds
   
   [Timer]
   OnBootSec=5
   OnUnitActiveSec=5
   Unit=vpn-status.service
   
   [Install]
   WantedBy=timers.target

5. Enable and Start the Service and Timer

1. Reload the systemd daemon to recognize the new service and timer:

   sudo systemctl daemon-reload

2. Enable and start the timer:

   sudo systemctl enable vpn-status.timer
   sudo systemctl start vpn-status.timer

3. Check the status of the timer and service:

   systemctl status vpn-status.timer
   systemctl status vpn-status.service

6. Verify VPN Status in tmux

1. Open tmux and confirm that the VPN status is displayed on the right side of the tmux status bar. The status should update every 5 seconds.

7. Debugging and Logs

To check logs or troubleshoot any issues:

journalctl -xe