As noted in my recent post about switching to Njalla from Cloudflare, I was searching for a way to replace my very easy-to-use bash script to update Cloudflare's DNS via their API.
To reiterate what I said in those posts, this is a common necessity for those of us who have non-static IP addresses that can change at any moment due to ISP policy.
In order to keep a home server running smoothly, the server admin needs to have a process to constantly monitor their public IP address and update their domain's DNS records if it changes.
This post explains how to use Python to update Njalla's DNS records whenever a machine's public IP address changes.
Creating a Token
To use Njalla's API, you will first need to create a token that will be used to authenticate you every time you call the API. Luckily, this is very easy to do if you have an account with Njalla.
Simply go the API Settings page and
Add Token button. Next, enter a name for the
token and click
Finally, click the
Manage button next to your newly created
token and copy the
API Token field.
Finding the Correct API Request
Once you have a token, you're ready to call the Njalla API for any number of requests. For a full listing of available requests, see the Njalla API Documentation.
For this demo, we are using the
list-records request requires the following payload to
be sent when calling the API:
edit-record request requires the following payload to
be sent when calling the API:
To create this script, we will be using Python. By default, I use Python 3 on my servers, so please note that I did not test this in Python 2, and I do not know if Python 2 will work for this.
Creating the Script
First, find a suitable place to create your script. Personally, I just
create a directory called
ddns in my home directory:
Next, create a Python script file:
The following code snippet is quite long, so I won't go into depth on each part. However, I suggest you read through the entire script before running it; it is quite simple and contains comments to help explain each code block.
:warning: Note: You will need to update the following variables for this to work:
token: This is the Njalla API token you created earlier.
user_domain: This is the top-level domain you want to modify.
include_subdomains: Set this to
Trueif you also want to modify subdomains found under the TLD.
True, you can include your list of subdomains to be modified here.
# -*- coding: utf-8 -*-
# Import Python modules
# Set global variables
# Main API call function
# Gather all DNS records for a domain
# Update a DNS record for a domain
# Get public IP addresses
# Call API to get all DNS records
# Loop through records and check if each one is IPv4 (A) or IPv6 (AAAA)
# Update only if DNS is different from server IP
Running the Script
Once you've created the script and are ready to test it, run the following command:
Setting the Script to Run Automatically
To make sure the scripts run automatically, add it to the
cron file so that it will run on a schedule. To do this,
In the cron file, paste the following at the bottom of the editor in order to check the IP every five minutes: