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README.md

🇵🇱 Polish version

IONOS DDNS Auto-Updater & Creator

A Python-based system service that automatically updates DNS records on IONOS. Unlike standard DDNS scripts, this solution uses the IONOS REST API, allowing it to:

Update existing DNS records.
Create new DNS records automatically if they don't exist.
Check the current DNS value before updating to avoid API rate limits.

Features

Smart Check: Compares public IP with current DNS resolution before sending API requests.
Auto-Discovery: Automatically detects which DNS Zone a subdomain belongs to.
System Service: Runs as a background systemd service with crash protection.
Logging: Detailed logs in /var/log/ionos-ddns.log.

Prerequisites

Python 3
An IONOS account with access to the "Developer API".
An API Key (Prefix + Secret) generated at developer.hosting.ionos.com.

Installation

1. Clone the repository to `/opt`

It is recommended to install this in a system directory.

sudo mkdir -p /opt/ionos-ddns
cd /opt
sudo git clone https://git.invelio.co.uk/rafal/ionos-ddns.git
cd /opt/ionos-ddns

2. Install dependencies

sudo apt update
sudo apt install python3-pip
sudo pip3 install -r requirements.txt

3. Configuration

sudo nano config.json

Fill in your api_prefix and api_secret.

Domains List: Edit domains.txt and add domains one per line:

sudo nano domains.txt

Example:

mydomain.com
vpn.mydomain.com
server.other-domain.net

IMPORTANT: Secure your API keys! Since config.json contains sensitive credentials, restrict access to it so only the root user can read it:

sudo chown root:root /opt/ionos-ddns/config.json
sudo chmod 600 /opt/ionos-ddns/config.json

Make script executable:

sudo chmod +x /opt/ionos-ddns/update_ddns.py

4. Install System Service

Copy the service file to systemd directory:

sudo cp ionos-ddns.service /etc/systemd/system/

Reload daemon, enable and start the service:

sudo systemctl daemon-reload
sudo systemctl enable ionos-ddns.service
sudo systemctl start ionos-ddns.service

Monitoring

Check the service status:

sudo systemctl status ionos-ddns.service

View logs:

tail -f /var/log/ionos-ddns.log

How it works

The script runs in an infinite loop (every 10 minutes).

Fetches your current Public IP.

Reads domains.txt.

For each domain:

Finds the correct Zone ID via API.

Checks if an A-Record exists.

If exists: Checks if IP matches. If not, performs PUT (Update).

If missing: Performs POST (Create).

ERROR

This error (400 Invalid API key format) means that the IONOS server rejected the key because its structure is incorrect. The most common causes are: Extra spaces (accidentally copied when pasting). Manually adding a dot in the config file (the script adds the dot automatically). Using the wrong type of key (Cloud API key instead of Hosting/DNS API key). Here is how to fix it step by step.

sudo nano /opt/ionos-ddns/config.json

Make sure the quotation marks are placed directly against the characters, with no spaces. WRONG (note the spaces):

"api_prefix": " 23498723498 ",
"api_secret": " a1b2c3d4 "

CORRECT:

"api_prefix": "23498723498",
"api_secret": "a1b2c3d4"

Do not add a dot in config.json The Python script contains this line:

"X-API-Key": f"{prefix}.{secret}"

It automatically joins these two values with a dot. If you entered in config.json something like: prefix: "myPrefix." then the script sends: "myPrefix..secret" (two dots), which causes the error. api_prefix: Only the first part of the key. api_secret: Only the second, long part of the key.