Зачем нужен hostname на VPS и как он связан с fqdn?
В данном случае виртуальному серверу (VPS) присваивается некоторое имя — hostname, которое, как правило, задается на этапе установки OS но позже может быть изменено.
Для чего нужно имя (hostname)?
Во -первых для идентификации сервера, при большом парке серверов необходимо точно понимать, на каком серевере ты находишься. По этой причине hostname должен быть уникальным.
Во-вторых, для выполнения обращения к серверу по имени (удаленный доступ, авторизация на сервере, выполнение удаленных команд).
Для доступа к серверу по имени нужно чтоб это имя резолвилось (преобразовывалось в IP-адрес) со стороны адресанта. Это условие выполняется если:
— локальный DNS сервер адресанта резолвит hostname адресата;
— hostname прописан вручную в «/etc/hosts», тогда преобразование имени будет происходить без DNS сервера.
Следует отметить, что в OS Windows обращение к серверу возможно по hostname, тут будет работать механизм NetBIOS.
FQDN и Hostname могут как отличаться, так и быть идентичными.
Очень часто значение FQDN понимают как публичную DNS запись типа А ( A-record), это делает данную запись уникальной.
Однако FQDN может быть уникальным только в пределах определенного сегмента сети или домена, который обслуживается своим DNS.
Почему некоторое ПО проверяет fqdn?
Программное обеспечение выполнит резолвинг fqdn-имени и попробует сравнить полученный IP-адрес преобразования с ip-адресом самого хоста. Таким образом сверка IP-адресов может быть проверкой корректности настроек.
В описанном случае с 10-20 сайтами и почтой на каждом из них , следует понимать, что у каждого сайта есть своё доменное имя, которое сконфигурировано через VirtualHost. По этому можно рекомендовать указать fqdn которое соответствует hostname с доменным именем (проверить можно через команду «hostname -A») и при этом резолвятся в небходимый IP.
FQDN (Fully Qualified Domain Name): What It Is, Examples, and More
A fully qualified domain name (FQDN) is a part of the uniform resource locator (URL). As the name suggests, it is the full name of an entity in the internet framework, including a host and a computer.
This article will explain the fully qualified domain name’s definition, examples, and functions. Then, we will walk you through how to find an FQDN on the three most commonly used operating systems – Windows, macOS, and Linux.
What is FQDN?
A fully-qualified domain name (FQDN) is a complete domain name that specifies the exact location of a computer or a host on the internet. It consists of the hostname and domain name. In addition, a FQDN can be found through terminal on MacOS and Linux or through the advanced system settings on Windows.
Examples of an FQDN
A fully qualified domain name, also known as an absolute domain name, specifies all domain levels written in the hostname.domain.tld format. For example, a mail server of yahoo.com would be mail.yahoo.com. Other examples include www.wordpress.org and news.bbc.co.uk.
Also you may want to read our article explaining what a domain name is.
Let’s explore each element on an FQDN hierarchy:
- Hostname. It is a label assigned to a server service available on a network. A DNS server uses a hostname to make an IP address easy to remember. Examples of a hostname are “www” in www.hostinger.com and “en” in en.wikipedia.org. . This part is located on the left side of a second-level domain and sometimes indicates a section of a larger domain. For instance, support.hostinger.com is a part of hostinger.com, and the word “support” is the subdomain. Note that not all domains have this element.
- A domain name. It consists of a second-level and a top-level-domain (TLD). For example, in hostinger.com, “hostinger” is the second-level domain, and “.com” is the TLD.
The maximum hostname and fully qualified domain name length is 63 bytes per label and 255 bytes per FQDN.
Important! Fully qualified domain names need a final dot or a trailing period at the right end to indicate the end of the name, such as www.hostinger.com. However, web browsers today usually assume there is a dot already and ensure you always have an FQDN.
What Is a Partially Qualified Domain Name?
Like an FQDN, a partially qualified domain name (PQDN) also indicates a web address but only includes a hostname or a domain name.
Generally, website developers configure their sites’ DNS to redirect visitors to the same page whether they type the FQDN or PQDN.
For example, if you type hostinger.com or www.hostinger.com, you will land on https://hostinger.com – the URL for our homepage. PQDNs are usually favorable since they are shorter, helping visitors find the site easier.
When to Use an FQDN
FQDNs are usually used in any interaction on the internet as they are easier to remember than IP addresses. Below are several scenarios of when to use an FQDN:
- Getting an SSL certificate. A secure sockets layer (SSL) protects a connection between a web server and a browser. An SSL certificate is issued to an FQDN, so you may not be able to use SSL services properly without it.
- Connecting to a remote host. You can make a remote host or a virtual machine by specifying any FQDN, enabling the DNS to look at its DNS table and locate the server. If you use only the hostname to connect to a server, your application may not be able to resolve the hostname.
- Accessing a specific domain service or protocol. Activities transferring information across a network generally involve the DNS, including pointing to an FQDN. An example is when you connect to a File Transfer Protocol (FTP) or an email server.
- Migrating to a new server. If you want to migrate your service to a server with a different IP address, using an FQDN instead of an IP address lets you quickly change the DNS record and reduce outages in the IP address changes.
Where to Find an FQDN
Follow the steps below to find an FQDN on any desktop for Windows users:
- Go to the Start Menu button and type “device name”. Click the View Your PC Name menu.
- Select Advanced system settings, and you should see the Full Computer Name section – that’s the FQDN.
Alternatively, use a simple command by right-clicking on the Start Menu and selecting Windows Terminal. Then, enter the ipconfig /all command to reveal a complete Windows IP configuration, including the hostname, primary DNS suffix, and connection-specific DNS Suffix.
For macOS users, click the System Preferences icon in the Dock or navigate to the Apple menu at the left top, select System Preferences, and choose Sharing.
At the top, you should see an FQDN and a connection-specific DNS suffix under the Computer Name section.
Meanwhile, Linux users can find FQDN by entering the hostname –fqdn command line in the Terminal. To open the Terminal, press CTRL + ALT + T or search for it by clicking the Dash icon, typing “terminal” in the search box, and selecting the Terminal application.
Conclusion
A fully qualified domain name (FQDN) enables a specific computer or a server on the internet to be uniquely identified within the domain name system (DNS).
This full domain name contains:
- Hostname
- Subdomain (if any)
- Second-level domain
- Top-level domain (TLD)
- Trailing period
Unlike fully qualified domain names, including complete levels of a domain, partially qualified domain names (PQDNs) consist of only the hostname or domain name – a second-level domain and a domain extension. Since it is shorter, a PQDN helps people remember the address much more quickly.
FQDNs are essential when you want to obtain an SSL certificate, migrate to a different server, or connect to a remote host or a virtual machine. Where to find an FQDN will depend on your operating system. For example, Windows and Linux-based users can check it using the Terminal, while Apple stores FQDNs on the System Preferences panel.
We hope this article helps you understand FQDN. If you’re planning to buy a domain name, make sure to check out our guide on how to buy a domain name. Let us know if you have any questions by leaving comments below.
Suggested Readings
FQDN FAQ
What Is FQDN vs DNS?
FQDNs enable computers and servers connected to the internet to have unique identities and a location within the internet framework. DNS, on the other hand, locates and translates domain names into IP addresses.
How Do I Find My FQDN Name?
On Windows, open the control panel and click on the system menu. Under the system information, you should see a hostname and the FQDN of your computer.
Can FQDN Be an IP Address?
Yes, FQDN can be assigned to an IP address. FQDNs contain both the host name and the whole domain name, including the TLD.
Lidin is passionate about online busines and marketing. She believes that these topics should be accessible to everyone, so she is determined to help people unlock their digital potential through written pieces. Outside her working hours, Lidin enjoys exploring new cities and editing videos.
FQDN – Definition, structure, syntax and examples
There is much more behind a domain than one imagines. They conceal a unique technical cosmos. Their resolution in the domain name system (DNS) is a complex process, as each computer, each domain and each IP address must be unambiguously identifiable. How does this work? This is where the so-called fully qualified domain name (short FQDN) comes into play.
Fully qualified domain name – a definition
The term fully qualified domain refers to a domain name that fully specifies the unique and exact location of a domain name within the DNS. The DNS provides the syntax. An FQDN is made up of individual labels that are each delimited by a dot and represent the different levels of the FQDN.
[hostname].[domain].[tld] -> [www].[internetx].[com]
The FQDN is relevant whenever a connection to the host is established. The DNS server resolves the hostname to its IP address by querying the DNS database. So, an FQDN shows the absolute path to a host and displays its IP address in a complete form that is legible to users.
There are a few rules for these so-called “absolute addresses”:
- The entire FQDN may have a maximal length of 255 characters.
- Only numbers, letters and hyphens are allowed.
- A number or letter must take the first position of each label.
How is a fully qualified domain name structured?
The hierarchy levels of an FQDN are read from right to left. The root label, also known as the null label, takes the highest hierarchy level and is therefore, as the name suggests, the root of the DNS system. It consists of an empty string and is indicated with a simple full stop. As all browsers now add this dot automatically, users no longer need to enter it.
The further right it is positioned, the higher the level held in the DNS. So the domain holds a higher level than a subdomain.
Let’s take a look at the structure of an FQDN by using www.internetx.com as an example:
Root domain
While most people are aware of the reading direction for domain names, the root domain usually remains hidden. It is the basis of the DNS system and is also called null or root label. It is made up of an empty zero-length string consisting of a single octet of zeros. In an FQDN, which strictly follows syntax, it is simply indicated by a dot.
Technically, a top-level domain is therefore in actual fact also a subdomain of the root domain. The root domain itself is automatically added by browsers, which is why they are generally not included in the FQDN.
Top-level domain
In our example, the top-level domain is ".com". Under this domain extension, the actual desired domain name can be selected in accordance with the guidelines of the respective registry.
Second-level domain
The second-level domain constitutes the address referred to as “domain”. Occasionally, the registry specifies that the second-level domain is predetermined and the selectable name is located on the third level – as is the case with .uk domains. Under .uk, domains can only be registered under the extensions .co.uk, .org.uk etc. but not directly under .uk. The same applies to domains under the Australian top-level domain. Starting March 2022, it will be possible to register second-level domains as domain names directly under .au. Until then, only third-level registrations are possible, e.g. under .com.au.
Hostname
As mentioned before, FQDNs are read from right to left. Between the second-level domain and the hostname, further subdomains may be included, numbered consecutively as third-level domain, fourth-level domain and so on. Farthest left, the hostname follows at the end. In our example https://www.internetx.com/domains/, the hostname is “www.” So, while a host name is always a subdomain, a subdomain is not necessarily already the hostname.
What is the difference between FQDN, FQHN and PQDN?
Via a fully qualified hostname (FQHN), a query reaches a unique and unambiguously identifiable computer. Its address is indicated through an IP or an FQDN.
An example: The computer with the name “mycomputer” can either be reached via the FQDN mycomputer.internetx.com or via an IP address, such as the fictive example 85.236.36.86.
By contrast, the partially qualified domain name (PQDN) is a relative name for a domain. It does not provide the complete path to the top-level domain. The name “mycomputer” is the PQDN in our example mycomputer.internetx.com.
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What is FQDN? What does FQDN do?
FQDN, another hard-to-pronounce abbreviation. You don’t really need to know it to get a domain and set it up, but for the more curious of you, here it is.
Table of Contents
What is FQDN?
The popular acronym FQDN stands for Fully Qualified Domain Name. It represents the fullest possible domain name of a host or a computer on the internet. In addition, it could be related to a website or to a server.
As you probably know, the Domain Name System (DNS) is decentralized, and it is built in a very precise hierarchical order. The Root is the beginning and above everything else, and one level below is the Top-Level Domain (TLD). The following component in the hierarchical order is the domain, and finally, the last important element is the precise hostname.
- FQDN Syntax
Here you can see the syntax of it:
[hostname].[domain].[tld]
It can also include a subdomain. Yet, you should know that the subdomain is not the hostname. It is just a part of the domain.
- FQDN Example
Let’s see an example of FQDN using cloudns.net. We read it from right to left.
www.cloudns.net
First is “.net“, which is the Top-Level Domain (TLD). Then it follows the domain name “cloudns“, and the last is the hostname “www.“.
The hostname can show a specific service or protocol for the domain like “mail” or “ftp”.
The FQDN serves to show the exact location of an object inside the DNS hierarchy.
Structure and elements of FQDN
The Fully Qualified Domain Name (FQDN) actually has a very simple and easy-to-understand structure and three main elements. So, let’s explain a little bit more about them:
TLD (Top-Level Domain): It is shown with all of the standard extensions that are located at the very end of an FQDN. They usually are very short, and their length is just 2 or 3 letters. Some popular examples are .com, .edu, .uk, etc. Of course, in the present days, you can find TLDs that are a little bit longer than that. For instance, there are .systems, .company, etc.
Domain: It stands exactly after the Top Level Domain (TLD) and is very well-known, and regular users are familiar with it. Here is a simple illustration – example.com.
Hostname: You can also identify it with ease. It is represented by the symbols at the very beginning of the Fully Qualified Domain Name (FQDN). Here a widespread and familiar example is www in www.example.com. Some domain owners could create different hostnames based on the need of their domain name. Each of them is going to be related to the domain. Several examples of such different hostnames are:
- www.example.com
- ftp.example.com
- mail.example.com
What is PQDN?
The short acronym PQDN stands for Partially Qualified Domain Name and it simply represents an FQDN (Fully Qualified Domain Name) with a missing part. It does not include all of the elements that provide the precise position on the DNS hierarchy. It is just a part of the complete domain name.
To make things more simple, let’s use the ClouDNS domain name again for an illustration. The PQDN is, for example, “cloudns.net“. In this one, we don’t have the host “www.“.
Many users use PQDN daily without even knowing it. The reason for that is simple. PQDN is more accessible and easy to use. In addition, it is shorter, which makes daily searches quicker and easier.
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How to make a FQDN lookup?
You can perform an FQDN lookup on your computer with any of the popular operating systems (OS).
Windows 10
Here is how to see the FQDN on a Windows 10 device:
- Click on the Start menu, type “Control Panel,” and click it.
- Inside the Control Panel, find “System” and open it.
- Inside the System, look for “Device specifications” and search for the “Full Computer Name.”
- There is the FQDN.
macOS
If you are using macOS, follow these next steps to find the FQDN.
- Open the Terminal application.
- Inside, type the following command: “hostname -f” and press the Enter button. The option “-f” means full.
- You will see the FQDN.
Linux
If you are a Linux user, you can find the FQDN similar to the macOS.
- Open the Terminal application.
- Inside, type the following command: “hostname -A” and press the Enter button.
- You will see the FQDN.
Why do you need FQDN?
Here are some of the main cases when FQDN comes in hand:
- You will need FQDN to make a device accessible on the internet. You will use it to configure your DNS and get an IP address.
- Another use case is when you want to get an SSL certificate. Today, almost every site has one, and you need to provide the FQDN to obtain it.
- Remote Access. The DNS server will perform a lookup in its registers and resolve the FQDN to the correspondent IP address.
- Access a protocol or a service. If you want to use a FTP for example, you will need the Fully Qualified Domain Name or IP. Also, for setting up email for specific applications, you will need it.
Conclusion
Fully Qualified Domain Name is used all the time, even if you don’t see it directly. It is the full identifier of the domain names.
Hi, I’m Martin Pramatarov. I have two degrees, a Technician of Computer Networks and an MBA (Master of Business Administration). My passion is storytelling, but I can’t hide my nerdish side too. I never forgot my interest in the Hi-tech world. I have 10 years and thousands of articles written about DNS, cloud services, hosting, domain names, cryptocurrencies, hardware, software, AI, and everything in between. I have seen the Digital revolution, the Big migration to the cloud, and I am eager to write about all the exciting new tech trends in the following years. AI and Big Data are here already, and they will completely change the world!
