ddclient is a very useful tool for most of us who run servers, or any kind of service, from home with a dynamic IP address. ddclient is capable of working with many dynamic dns providers, but I found that documentation was lacking for using with Namecheap DNS which is who I use. So here's a short little guide for installing and setting up ddclient to automatically update your dynamic dns address for a domain hosted with Namecheap, specifically with a sub-domain.

Let's Get Started!

1.) installation:

yum -y install epel-release && yum -y update   # Install EPEL repository, and update
yum -y install ddclient   # Install ddclient from EPEL

2.) configure ddclient:

mv /etc/ddclient.conf /etc/ddclient.conf.orig   # Backup default config
vi /etc/ddclient.conf

---
################
### ddclient.conf
### namecheap
##################
daemon=300                          # Time, in seconds, to check for IP change and to send update
ssl=yes                         # Whether to use ssl to send update; you want this
use=web, web=checkip.dyndns.com/, web-skip='IP Address' # Leave these settings as is
protocol=namecheap                      # This tells ddclient that we are using namecheap
server=dynamicdns.park-your-domain.com          # Server name for namecheap's dynmic dns service; do not modify
login=deviantengineer.com                   # Your root domain name that you want to update dynamic dns on
password=randomstringofcharacters               # This is your dynamic dns password, provided by namecheap
photoalbum                          # OPTIONALLY, set a HOST value if you want to apply this to a sub-domain
---

So this is really all it takes to make ddclient work with Namecheap. A few of these settings were ambiguous when I was first setting up ddclient, and I had a lot of trial and error, which lead me to throwing this blog together.
Most important here is login, password, and the HOST value below that (if used). login is where you set the root of your domain. For me and this blog, I would use deviantengineer.com and nothing else. In this scenario, I am wanting to set ddclient to update my IP for photoalbum.deviantengineer.com, but I still only want to list the base domain in this login field.
The password field comes from namecheap. In your dns settings area of a domain, under the DYNAMIC DNS section, you will find the Dynamic DNS Password. Put that password on this key.
Lastly is the optional sub-domain field. This was something I struggled with finding, but finally figured out. Since ddclient already knows about deviantengineer.com, all I need to set here is photoalbum in order to have dynamic dns update the photoalbum.deviantengineer.com (no, this is not a real sub-domain of mine; made up for this blog only). If you are setting dynamic dns on the base domain, delete this line in ddclient.conf.

4.) cleanup:

systemctl enable ddclient.service
systemctl restart ddclient.service

And that's it. Pretty straightforward and simple, but surprisingly difficult to find clear and concise documentation. Now if you are using this with a different dynamic dns provider, I'm afraid I can't help with that. I exclusively use Namecheap so that were my experience and knowledge ends.

Enjoy!