🛠Auto Update IP of EC2 With DuckDNS

DuckDNS Auto Update IP Setup on EC2 Startup

This guide will walk you through setting up a script that updates DuckDNS with your EC2 instance's public IP at startup.

1. Create the setup-duckdns.sh file

Run the following commands to create the update script:

vim setup-duckdns.sh

Paste the content below into the file:

#!/bin/bash

# === CONFIGURATION ===
DUCKDNS_DOMAIN="your-subdomain"     # e.g., nikitech
DUCKDNS_TOKEN="your-token"          # e.g., 0123abcd-4567efgh...

USER_HOME=$(eval echo ~${SUDO_USER})
SCRIPT_PATH="$USER_HOME/update_duckdns.sh"

echo "📦 Creating DuckDNS update script at $SCRIPT_PATH"

# Create the DuckDNS update shell script
cat <<EOF > $SCRIPT_PATH
#!/bin/bash
echo "[\$(date)] Updating DuckDNS..." >> /var/log/duckdns.log
curl -s "https://www.duckdns.org/update?domains=$DUCKDNS_DOMAIN&token=$DUCKDNS_TOKEN&ip=" >> /var/log/duckdns.log
echo "" >> /var/log/duckdns.log
EOF

chmod +x $SCRIPT_PATH

# Create the systemd service
SERVICE_FILE="/etc/systemd/system/duckdns-update.service"
echo "🛠️  Creating service at $SERVICE_FILE"

cat <<EOF | sudo tee $SERVICE_FILE > /dev/null
[Unit]
Description=Update DuckDNS IP at startup
After=network.target

[Service]
Type=oneshot
ExecStart=$SCRIPT_PATH
RemainAfterExit=true

[Install]
WantedBy=multi-user.target
EOF

# Reload systemd and enable the service
echo "🔁 Reloading systemd and enabling the service..."
sudo systemctl daemon-reexec
sudo systemctl daemon-reload
sudo systemctl enable duckdns-update.service

echo "✅ Completed! DuckDNS will be updated each time EC2 starts."
echo "📄 Logs will be saved to: /var/log/duckdns.log"

2. Run the .sh file on EC2

Step 1: Grant execute permission

chmod +x setup-duckdns.sh

Step 2: Run with root privileges (use sudo)

sudo ./setup-duckdns.sh

⚠️ Note:

If you're using Amazon Linux 2023, the script will work as expected because it uses systemd.

If you're using Ubuntu 20.04 or 22.04, it is also fully compatible.

3. Verify the setup

After completing the setup:

Restart EC2:

sudo reboot

Check the DuckDNS log:

cat /var/log/duckdns.log

You should see a line like this in the log:

[Mon Apr  1 12:00:00 UTC 2025] Updating DuckDNS...
OK