How to get fqdn

What is a Fully Qualified Domain Name (FQDN)?

A Fully Qualified Domain Name (FQDN), also sometimes referred to as an absolute domain name, is the complete domain name for a specific computer, or host, on the internet. It is a hierarchical naming convention that uniquely identifies a device's location within the Domain Name System (DNS). Think of it like a full postal address for a computer on the internet; it leaves no room for ambiguity about which specific resource is being referenced.

An FQDN is composed of several parts, read from right to left: the Top-Level Domain (TLD), the domain name, and the hostname (or subdomain). For instance, in the FQDN www.example.com:

• .com is the Top-Level Domain (TLD). TLDs are the highest level in the DNS hierarchy, such as .com, .org, .net, .gov, .edu, or country-specific ones like .uk, .ca, .jp.
• example is the domain name. This is typically registered by an individual or organization.
• www is the hostname. This is a specific machine or service within the domain. It could be a web server, mail server, or any other internet-connected device.

Technically, a true FQDN ends with a dot (.), representing the root of the DNS hierarchy. So, the FQDN for www.example.com would be www.example.com.. While this trailing dot is often omitted in everyday usage and many applications will append it automatically, it is part of the complete and unambiguous FQDN.

Why are FQDNs Important?

FQDNs are fundamental to how the internet functions. They serve several critical purposes:

• Unambiguous Identification: In a vast network like the internet, FQDNs ensure that every host can be uniquely identified. This prevents confusion and ensures that requests are directed to the correct destination.
• DNS Resolution: When you type an FQDN into your web browser (e.g., www.google.com), your computer uses the DNS to translate this human-readable name into a numerical IP address (like 172.217.160.142) that computers use to communicate. The FQDN is the key piece of information that the DNS system uses to perform this translation.
• Network Routing: Routers on the internet use IP addresses to direct data packets to their destinations. The DNS, using FQDNs, provides the bridge between human-readable names and these machine-readable IP addresses, enabling efficient routing.
• Service Accessibility: FQDNs are used to access various internet services, not just websites. For example, mail servers often have FQDNs like mail.example.com, and other services might use different hostnames within a domain.
• Security and Management: FQDNs are also important for security protocols like SSL/TLS certificates, which are issued for specific domain names to secure web traffic. They also aid in network administration and management by providing a structured way to name and organize devices.

How to Determine an FQDN

You can often determine the FQDN of a device or service in several ways:

1. On Your Own Computer (Windows)

To find the FQDN of your own Windows computer:

1. Right-click on the Start button and select System.
2. Under 'Device specifications', you will see 'Computer name'.
3. Under 'Computer name, domain, and workgroup settings', you will see 'Full computer name'. This is your computer's FQDN. If it shows a domain name (e.g., mycomputer.mydomain.local), that's your FQDN. If it doesn't show a domain name and only shows the computer name (e.g., MYDESKTOP), your computer is likely part of a workgroup, and its FQDN might be just the computer name followed by a local domain suffix if one is configured by your network administrator or ISP, or it might not have a publicly resolvable FQDN.
4. Alternatively, open Command Prompt, type ipconfig /all, and press Enter. Look for the 'Host Name' and 'Primary Dns Suffix' fields. Concatenating these (if a primary DNS suffix exists) gives you the FQDN.

2. On Your Own Computer (macOS)

To find the FQDN of your own macOS computer:

1. Click the Apple menu () in the top-left corner.
2. Select System Settings (or System Preferences in older macOS versions).
3. Click on General, then About.
4. Click on Network.
5. Click on Wi-Fi or Ethernet (whichever you are using).
6. Click the Details... button.
7. Go to the DNS tab.
8. Your computer's hostname is usually displayed at the top of the System Settings/Preferences window, often under 'Computer Name'. If your Mac is connected to a domain or has a specific network setup, the FQDN might be formed by appending the domain suffix to the hostname. You can also open the Terminal application and type hostname -f to display the FQDN.

3. Using Online Tools

There are online tools that can help you determine the FQDN of a website or server. You typically enter the domain name (e.g., google.com), and the tool will perform DNS lookups to find associated hostnames and their FQDNs.

4. From Network Administrators

If you are part of a corporate or organizational network, your IT department or network administrator is the best source for information about the FQDNs of devices within that network. They manage the DNS records and can provide the correct FQDNs for servers, workstations, and other resources.

Understanding the Difference: Domain Name vs. FQDN

It's important to distinguish between a domain name and an FQDN. A domain name, like example.com, refers to a specific domain in the DNS hierarchy. An FQDN, like www.example.com or mail.example.com, is a specific host *within* that domain.

The domain name itself (e.g., example.com) can be considered an FQDN for the domain's root or for specific services if no subdomains are used. However, when referring to a specific machine (like a web server), the FQDN includes the hostname.

Common Examples of FQDNs

• www.google.com: The FQDN for Google's main web server.
• mail.yahoo.com: An FQDN for a Yahoo mail server.
• en.wikipedia.org: An FQDN for the English version of Wikipedia.
• localhost: While often used to refer to the local machine, its FQDN is typically localhost. or localhost.localdomain depending on the system's configuration.

In summary, an FQDN is the complete, unambiguous address of a device on the internet, comprising its hostname and the full domain hierarchy it belongs to. It's a fundamental concept for understanding how networks and the internet operate.