This script will update the A DNS record for a domain/subdomain at NearlyFreeSpeech.NET with the public IP address for the machine the script runs on. Run this script on a server in which the public IP address is dynamic and changes so your domain is always up to date.

There are two steps to this script. First, it retrieves the configured IP address for the domain/subdomain, the current public IP address of the server, and then compares the two. If the public IP address is different, it updates the A record of the domain/subdomain with the new IP address.

Tcl, Tcllib, and TclTLS are the only requirements. They come pre-installed or are easily installed on most *nix operating systems.

Configurations are set by providing the script with environment variables

It is as easy as running: tclsh dns.tcl

or make it executable with chmod u+x dns.tcl and then run ./dns.tcl

To include all of the environmental variables inline when running, you can do something like this:

$ export USERNAME=username API_KEY=api_key DOMAIN=domain.com SUBDOMAIN=subdomain && ./dns.tcl

1. Set the configuration values in the script the way you want them (or create a file containing the environment variables)

2. Build the image with docker build -t nfs-dynamic-dns .

3. Run the image (production) with docker run -d --name nfsn-dynamic-dns nfs-dynamic-dns (add the --env-file <file> argument before the last nfsn-dynamic-dns if you want to use your environment variable file)

   Ex: docker run -d --name nfsn-dynamic-dns --env-file .env nfs-dynamic-dns

You can use the following config to run this with docker compose.

version: "3"

services:
  nfs-dynamic-dns:
    image: nfs-dynamic-dns
    build: ./nfs-dynamic-dns
    container_name: nfs-dynamic-dns
    network_mode: host
    environment:
     - USERNAME=username
     - API_KEY=api_key
     - DOMAIN=domain.com
     - SUBDOMAIN=subdomain
    restart: unless-stopped

To run the container locally (and let it run its cronjobs), use this command: docker run -it --rm --init nfs-dynamic-dns

to run the container locally and be put into a shell where you can run ./dns.tcl yourself use this: docker run -it --rm --init nfs-dynamic-dns sh

If your setup uses environment variables, you will also need to add the --env-file argument (or specify variables individually with the -e docker flag). The --env-file option is for docker run and the env file format can be found here.

It can be setup to run as a cron job to completely automate this process. Something such as:

@hourly /usr/local/bin/tclsh /scripts/nfs-dynamic-dns/dns.tcl

When using the Docker file, it's by default scheduled to run every 30 minutes. However, this is configurable when building the container. The CRON_SCHEDULE build arg can be overriden.

With docker, the build step (step 2) can be done like this:

$ docker build --build-arg CRON_SCHEDULE="*/5 * * * *" -t nfs-dynamic-dns .

With docker compose, it can be done like this:

version: "3"

services:
  nfs-dynamic-dns:
    image: nfs-dynamic-dns
    build:
      context: ./nfs-dynamic-dns
      args:
        - CRON_SCHEDULE=*/5 * * * *
    container_name: nfs-dynamic-dns
...

The script communicates with NearlyFreeSpeech.NET via its RESTful API. Specifics about the API can be found here.