Linux (Generic)

Set up automatic DDNS updates on any Linux system using cron.

Confirm curl is installed

Most Linux systems include curl. Check with:

bash

which curl
# If missing, install it:
# Ubuntu/Debian: sudo apt install curl
# CentOS/RHEL:   sudo yum install curl

Test your check-in URL

Run a manual check-in to confirm everything is working:

bash curl -s "https://greatddns.com/api/checkin/?token=YOUR-DEVICE-TOKEN"

Expected response: {"status": "ok", "ip": "x.x.x.x", "changed": true/false}

Add a cron job

Open your crontab and add the check-in command to run every 5 minutes:

bash crontab -e

Add this line to your crontab

In the editor that opens, add the following line at the bottom:

bash */5 * * * * curl -s "https://greatddns.com/api/checkin/?token=YOUR-DEVICE-TOKEN" > /dev/null 2>&1

Save and exit (Ctrl+X then Y in nano, or :wq in vi). The cron daemon picks up changes automatically.

Verify the cron job

Confirm your cron entry was saved:

bash crontab -l

If you want to log check-in output for troubleshooting, use: */5 * * * * curl -s "{{CHECKIN_URL}}" >> /var/log/greatddns.log 2>&1