1. start your daemon, 2. verify default location of .conf on your system, 3. overwrite it with this minimal confi. (for me it's `/etc/ddclient/ddclient.conf`)

ddclient.conf

# AUTHOR'S NOTE
# 
# minimal ddclient config that i use
# i recommend using 1984.is or freemyip.com
# both registries are free and don't have KYC
# 
# test config:
# $ ddclient -daemon=0 -verbose -noquiet
# test ip:
# $ ddclient -query
# 
# READ THIS:
#
# you have to (!) set the creds for your DNS provider:
# $ export DDCLIENT_LOGIN=foobar
# $ export DDCLIENT_PASSWORD=foobar
#
# SET THESE VALUES:

YOUR_DOMAIN.com  # can add more comma separated hostnames
server=DNS_DOMAIN.com  # 1984.is, freemyip.com are both good no-kyc options  

# CHANGE IF NEEDED:

#use=if, if=eth0
#use=ip, ip=127.0.0.1
use=web

#proxy=

#mx=mail.YOUR_DOMAIN.com
#mail=root          # mail all messages to root
#mail-failure=root  # mail failed updates to root
#ttl=1

# ----------------

login_env=DDCLIENT_LOGIN
password_env=DDCLIENT_PASSWORD
pid=/var/run/ddclient.pid
syslog=yes
ssl=yes
daemon=600  # 600 (10min) is the minimum for some services