OS: Ubuntu 6.06 LTS Server Ed.
Software: ddclient 3.7.3 (supports Ubuntu)
First, download ddclient from here and use tar command to extract the files. Since I saved the downloaded file in /home/user/ directory, I didn't have to change directory. Otherwise use cd command to change directory first. Note: You need to change file name and folder name as necessary.
Next, copy ddclient script, make directory for ddclient, and configuration file by
Use vi to edit ddclient configuration file. I use DynDNS and their knowledge base has an article on how to configure ddclient.
After making necessary changes in ddclient.conf, copy the following file to /etc/init.d folder so that ddclient can run as a daemon.
Next, add ddclient to all run levels by
Start ddclient manually for the first time by
That's all. Check to make sure ddclient is working.
Note: One can also use apt-get to install ddclient from Ubuntu's repository by using the following command. Make sure to check here first before using apt-get to install.