sudo apt-get install ddclient libdata-validate-ip-perl libjson-any-perl net-tools

Edit /etc/ddclient.conf as follows:

daemon=1800
syslog=yes
protocol=cloudflare
use=web
web=checkip.dyndns.org/ 6
web-skip=‘IP Address’
ssl=yes
login=<Cloudflare Login>
password=<APIKEY>
zone=example.com
host.example.com

Verify the config:

sudo service ddclient status
sudo ddclient -query
sudo ddclient -daemon=0 -verbose -noquiet

Enable the service:

sudo service ddclient status

Set Hostname

sudo hostnamectl set-hostname whatever.example.com