dyndns and ddclient configuration under grml linux (or, probably, other debian based distros)

Dynamic DNS allows you to have domain name with your dynamic ip address assigned by your local ADSL Internet.  One thing you need to do is to set up a dynamic dns client in a machine inside your local network where it uses your local ADSL Internet.   Nowaday, many ADSL routers support dyndns.  However, I'd prefer setting it up on a linux machine instead as I will surely have full control over the system.  By default, the configuration (/etc/ddclient.conf) in grml 2010.04 looks like this:

# Configuration file for ddclient generated by debconf

#

# /etc/ddclient.conf

protocol=dyndns2

use=web, web=checkip.dyndns.com, web-skip='IP Address'

server=members.dyndns.org

login=

password=''

This is not enough for my case.

After I spent time through trail and error I found I have to edit file /etc/default/ddclient:

set daemon_interval="60"

And in file /etc/ddclient.conf

# Configuration file for ddclient generated by debconf

#

# /etc/ddclient.conf

protocol=dyndns2

use=web, web=checkip.dyndns.com, web-skip='IP Address',

server=members.dyndns.org

login=your_username,

password='your_password',

yourpreferreddomainname.dyndns.org

The most important thing is that you have to provide your domain names on the last line which will get updated.  Note that I tried setting daemon_interval in /etc/ddclient.conf but it didn't work so I instead set it in /etc/default/ddclient.

I am sure there must be other settings that work too.  But I will just stick with this approach.