apt-get install ddclient
# /etc/ddclient.conf protocol=dyndns2 use=web, web=checkip.dyndns.com, web-skip='Current IP Address' server=www.ovh.com login=domain.tld-user password='password' subdomain.domain.tld
Per eseguire un test:
ddclient -daemon=0 -debug -verbose -noquiet