[script] Automatically Change Dns If Pi-hole Is No Longer Working

Mohammad

7 min read

·

Oct 06, 2024

65

Share

Automatically Changing DNS When Pi-hole Stops Working

Having a reliable DNS server like Pi-hole is crucial for internet security and content filtering. However, situations can arise where your Pi-hole might unexpectedly stop working, leaving your devices vulnerable and exposing them to unwanted content. This is where a script to automatically change DNS settings comes in handy.

Why Automate DNS Changes?

Imagine your Pi-hole goes down during the middle of the night. Your devices will continue to use the old DNS settings, potentially allowing access to malicious websites or exposing you to unwanted ads. Automating the DNS change process ensures that your devices will seamlessly switch to a backup DNS server, keeping your internet browsing safe even if your Pi-hole encounters issues.

How Does the Script Work?

The script works by constantly monitoring the status of your Pi-hole. It can achieve this by:

• Pinging: Regularly pinging your Pi-hole's IP address. If the pings fail, it signifies that the Pi-hole is down.
• DNS Queries: Sending DNS queries to your Pi-hole. If the responses are not received within a certain timeframe, it implies the Pi-hole is unresponsive.
• API Calls: If your Pi-hole is running a web interface, the script can utilize its API to check its status.

Once the script detects that the Pi-hole is down, it will execute the necessary commands to change your device's DNS settings. These commands could involve:

• Modifying Network Configuration: Changing the DNS settings within your operating system's network configuration.
• Modifying Router Settings: Updating the DNS settings on your router, which will automatically apply to all connected devices.
• Using a Dynamic DNS Service: Utilizing a service like DynDNS or No-IP to update your device's DNS settings remotely.

Example Script (Bash)

#!/bin/bash

# Define the Pi-hole's IP address
PI_HOLE_IP="192.168.1.100"

# Define the backup DNS server (e.g., Google DNS)
BACKUP_DNS="8.8.8.8"

# Ping the Pi-hole
ping -c 2 -W 2 $PI_HOLE_IP > /dev/null 2>&1

# Check if ping was successful
if [[ $? -eq 0 ]]; then
    echo "Pi-hole is up."
else
    echo "Pi-hole is down. Changing DNS settings to $BACKUP_DNS."

    # Replace with your specific command to change DNS settings
    # Example for Linux (network manager)
    nmcli connection modify "your-connection-name" ipv4.dns "$BACKUP_DNS"
fi

Explanation:

• The script begins by defining the Pi-hole's IP address and the backup DNS server's IP address.
• It then pings the Pi-hole twice, waiting for 2 seconds for each response.
• If the ping is successful, it prints a message indicating that the Pi-hole is up.
• If the ping fails, the script prints a message stating that the Pi-hole is down and it will change the DNS settings to the backup server.
• The script then executes the necessary command to change the DNS settings. Replace the example command with the appropriate command for your system and network configuration.

Note: This is a basic example. You may need to modify the script to fit your specific setup and requirements. You might need to adjust the ping count, the waiting time, or use different methods to check the Pi-hole's status.

Important Considerations

• Scheduling: You can schedule this script to run automatically at regular intervals using a tool like cron on Linux or Task Scheduler on Windows.
• Logging: Implement logging within the script to record when the Pi-hole goes down and when the DNS settings are changed. This will help you track the script's activity and troubleshoot any issues.
• Monitoring: Set up monitoring tools to alert you when the script detects a Pi-hole failure. This can be done using email notifications, SMS messages, or other notification services.
• Backups: Always ensure you have a backup of your DNS settings in case the script malfunctions or accidentally changes them to incorrect values.

Conclusion

Having a script to automatically change your DNS settings when your Pi-hole goes down ensures that your devices remain secure and protected from unwanted content. By automating this process, you can rest assured that your internet browsing will remain safe even in the event of Pi-hole issues. Remember to test the script thoroughly and adjust it to fit your specific network configuration.