Setting Up a Weekly Cron Job for Pi-hole Gravity Updates

In this blog post, I’ll walk you through the process of setting up a weekly cron job to send an SMS notification when the Pi-hole gravity update is completed. This setup is particularly useful if you’re running Pi-hole in a Docker container and want to ensure that your cron job persists across container restarts.

Prerequisites

A running Pi-hole instance in a Docker container.
Access to the host machine where Docker is running.
Basic knowledge of shell scripting and cron jobs.

Step 1: Create the Shell Script

First, create a shell script on the host machine that will be executed by the cron job. This script will update the Pi-hole gravity database and send an SMS notification upon successful completion.

Create the Script:

Open a text editor and create a new file named pihole_update_gravity_with_sms.sh:
```
sudo nano /usr/local/bin/pihole_update_gravity_with_sms.sh
```

Add the Script Content:

Copy and paste the following content into the file:

 #!/bin/bash
   
 # Path to the Pi-hole gravity update script
 GRAVITY_SCRIPT="docker exec pihole /usr/local/bin/pihole updateGravity"
   
 # SMS API credentials
 SMS_USER="USERNAME"
 SMS_PASS="APIKEY"
 SMS_MESSAGE="Pi-hole Gravity Update Completed Successfully."
   
 echo "Starting gravity update..."
   
 # Execute the gravity update
 \$GRAVITY_SCRIPT
   
 # Check if the gravity update was successful
 if [ \$? -eq 0 ]; then
     echo "Gravity update completed successfully."
   
     # Send notification via SMS using the confirmed working syntax
     echo "Sending SMS notification..."
     /usr/bin/curl "https://smsapi.free-mobile.fr/sendmsg?user=\${SMS_USER}&pass=\${SMS_PASS}&msg=\${SMS_MESSAGE}"
   
     echo "SMS notification sent successfully."
 else
     echo "Gravity update failed. No SMS notification sent."
 fi

Make the Script Executable:

Change the permissions of the script to make it executable:
```
 sudo chmod +x /usr/local/bin/pihole_update_gravity_with_sms.sh
```

Step 2: Add the Script to the Host’s Cron Schedule

Next, add the script to the host’s cron schedule to run it weekly at 5:30 AM every Monday.

Edit the Crontab:

Open the crontab file for editing:
```
 sudo crontab -e
```
Add the Cron Job Entry:

Add the following line to the crontab file to run the script at 5:30 AM every Monday:
```
 30 5 * * 1 /usr/local/bin/pihole_update_gravity_with_sms.sh
```
Save and Exit:

Save the changes and exit the crontab editor.

Step 3: Verify the Cron Job

To ensure that the cron job is set up correctly, you can manually trigger the script and check the logs for any output or errors.

Manually Run the Script:

Execute the script manually to verify that it works as expected:
```
 sudo /usr/local/bin/pihole_update_gravity_with_sms.sh
```
Check the Logs:

Review the system logs to see if the script was executed and if there were any errors:

bash sudo tail -f /var/log/syslog

Conclusion

By following these steps, you have successfully set up a weekly cron job to send an SMS notification upon the completion of the Pi-hole gravity update. This setup ensures that you are promptly notified of the update status, helping you maintain the efficiency of your Pi-hole instance.