What is FQDN (Fully Qualified Domain Name)

The FQDN stands for the longer Fully Qualified Domain Name. It is exactly what it says, the most full way to write a particular domain name (website or a server). As you know, DNS is a hierarchy system, starting from the root, then TLD, then the domain, and last is the particular hostname. 

Syntax of a fully qualified domain name: hostname.domainname.TLD ([hostname].[domain].[tld].)

Example of fully qualified domain names: mail.google.com, ftp.microsoft.com, movies.disney.com

Note that the last dot “.” (root) is often omitted, and the FQDNs usually end with the TLD. Yet, in some cases, you need to add, depending on what software you are using. 

The Fully Qualified Domain Name will show you where exactly an object is on the DNS hierarchy. 

Why do you need the FQDN?

1. To get an IP address and configure DNS, you will need the FQDN. Otherwise, you can make your computer accessible on the web. 
2. To get an SSL certificate. You need to get such a certificate to secure the communication between your site and the users, and for that, you need an FQDN. 
3. To use remote access. Your device will be the server, so it needs a name (FQDN) and an IP address to provide services over the Internet. 

Parts of the FQDN

1. Hostname. Usually, they indicate different services or subcategories, like mail, ftp, store, support, blog, etc.
2. Domain. The name that an owner or company has chosen like Google, Microsoft, Disney, or another. 
3. TLD. Depending on the domain name owner’s choice, it could be a ccTLD like .co.uk, .it, .bg, or a gTLD like .com, .info, .org, etc.

PQDN (Partially qualified Domain Name)

If you are missing a part from the Fully Qualified Domain Name, you are left with a Partially qualified Domain Name. It doesn’t have all the elements that will show you the exact location on the DNS hierarchy. Using the examples from before, google.com, microsoft.com, or disney.com are all PQDNs, because they are missing the web host (www.) before the domain name. 

People usually use PQDN because of the ease of use. Shorter is easier to remember and write. 

How can you see the FQDN of your device?

You can do an FQDN lookup on your device, no matter if you are on a macOS, Linux, or Windows 10 device. 

On macOS:

1. Open the Terminal application.
2. Write down the following command: “hostname -f” and press the Enter. The option “-f” means full. 
3. You will see the FQDN. 

On Linux 

1. Open the terminal application. 
2. Write down the following command: “hostname -f” and press the Enter.
3. You will see the FQDN. 

On Windows 10

1. Click the start menu, write “Control Panel”, and click it. 
2. Inside the Control Panel, find the System and open it. 
3. Inside the System, see the “Device specifications” and look for the “Device name”. 
4. Then is the FQDN. 

Conclusion

A Fully Qualified Domain Name is needed to pinpoint the exact location of a host. It is an accurate identifier, and computers need it for various services.