FQDNs

A fully qualified domain name (FQDN) is a complete name given to a host that resides within a domain. The domain could be generated by Active Directory/FreeIPA or part of a web server hierarchy. Regardless of the operating system, the naming convention is the same:
hostname + domain name = FQDN

For example: the hostname: workstation1 plus the domain name: example.local would become:

workstation1.example.local

Note: These are also known simply as "DNS names".

Check out the video below (and mini-lab) to learn how to work with hostnames in Linux.

VIDEO

Lab 24 ⚙️ Configuring a Hostname in the Terminal

We've done plenty up to this point with IP addresses. But most systems (and people) communicate by name. So a technician needs to know how to modify hostnames and configure DNS. Remember that the Domain Name System (DNS) is in charge of resolving domain names (and host names) to their respective IP addresses - and vice-versa.

Working with hostnamectl

• View system information with the hostnamectl command

  Type hostnamectl to see the hostname and other information about the system. Example:

  root@deb52:~# hostnamectl
    Static hostname: deb52
          Icon name: computer-vm
            Chassis: vm
           Location: workplace2
         Machine ID: 42f779dc9123405c90f8fa73b6c83f7c
            Boot ID: 35b9c976794a4bb38ba7a4e81511152a
     Virtualization: kvm
   Operating System: Debian GNU/Linux 10 (buster)
             Kernel: Linux 4.19.0-16-amd64
       Architecture: x86-64
  

  Here we see the name of the computer is deb52. We get a whole lot of other information as well, including the operating system type and version, the version of the Linux kernel, and the architecture of the computer.

• Use the hostnamectl command to change the hostname.

  • First, change the name by typing hostnamectl set-hostname newname
  • View the new name by entering hostnamectl
  • Close the terminal and open a new one to see the new name in the prompt.
  • Change the name back to the original.
  • Close the terminal and open a new one again.
  • Verify the name is back to the original. (You can also use the older hostname command to see the hostname only.)

  Example: (the four dashes represents closing the terminal and reopening it)

  root@deb52:~# hostnamectl set-hostname newname
  root@deb52:~# hostnamectl
     Static hostname: newname
           Icon name: computer-vm
             Chassis: vm
            Location: workplace2
          Machine ID: 42f779dc9123405c90f8fa73b6c83f7c
             Boot ID: 35b9c976794a4bb38ba7a4e81511152a
      Virtualization: kvm
    Operating System: Debian GNU/Linux 10 (buster)
              Kernel: Linux 4.19.0-16-amd64
        Architecture: x86-64
  ----
  root@newname:~# hostnamectl set-hostname deb52
  ----
  root@deb52:~# hostname
  deb52
  

  Note: A fun program that shows similar information to hostnamectl is called neofetch. Install it by name with your distro's installer - for example apt install neofetch. Then run the program by simply typing neofetch.

👍 Excellent work!

📚 Further Study

Be sure to check the help file and manual page for hostnamectl

• hostnamectl -h
• man hostnamectl