how-to install freedns-update on Ubuntu LTS to update your freedns domains (https://freedns.afraid.org/) if ip is changing.

sudo add-apt-repository ppa:mc-1/freedns-update
sudo apt-get update
sudo apt-get install freedns-update

set your freedns hash URL at

<ipcheck>
	url <place_your_update_url_here>
</ipcheck>

you can stop and start the service using

sudo start freedns-update
sudo stop freedns-update
sudo restart freedns-update

Started once it will be started automatically on system start (using upstart)