1. The static hostname is the most important one, and it’s stored in the /etc/hostname file. This hostname is used among machines to identify a particular server.
2. The pretty hostname got its name because it allows for more characters and punctuation. It’s more user-friendly, but since it uses non-standard characters, it is not permitted for machine code. The pretty hostname is stored in the /etc/machine-info directory.
3. The transient hostname is one maintained in the Linux kernel. It is dynamic, meaning it will be lost after a reboot. This approach might be useful if you have a minor job requiring a temporary hostname, but you don’t want to risk making a permanent change that might be confusing.

Check your current hostname

Method 1, use terminal

$ hostnamectl

$ uname -n

Method 2: use WHM Change Hostname

Change static hostname

$ hostnamectl set-hostname my.new-hostname.server
$ sudo vim /etc/hosts