Display the current RHEL 8 hostname

Type any one of the following command including the cat command:
$ cat /etc/hostname
OR
$ hostname
OR
$ hostnamectl

RHEL 8 change hostname command

The procedure to change the computer name on Red Hat Linux:

1. Type the following command to edit /etc/hostname using nano or vi text editor:
   sudo vi /etc/hostname
2. Delete the old name and setup new name.
3. Next Edit the /etc/hosts file:
   sudo vi /etc/hosts
4. Replace any occurrence of the existing computer name with your new one.
5. Reboot the system to changes take effect:
   sudo reboot

How to change the RHEL 8 server hostname without a system restart

Type the following commands:
$ sudo hostname nixcraft-rhel8
Next edit the /etc/hostname file and update hostname:
$ sudo vi /etc/hostname
Finally, edit the /etc/hosts file and update the lines that reads your old-host-name:
$ sudo vi /etc/hosts
From:
127.0.1.1 localhost
To:
127.0.1.1 nixcraft-rhel8
Save and close the file.

A note about hostnamectl command

Systemd based Linux distributions such as RHEL 8 can simply use the hostnamectl command to rename hostname. To see current setting just type:
$ hostnamectl
Sample outputs:

   Static hostname: localhost
         Icon name: computer-vm
           Chassis: vm
        Machine ID: 2f23e83aad5d413498ef79742ad660eb
           Boot ID: c3c158618d54451f82f3cee23471248d
    Virtualization: kvm
  Operating System: Red Hat Enterprise Linux 8.0 Beta (Ootpa)
       CPE OS Name: cpe:/o:redhat:enterprise_linux:8.0:beta
            Kernel: Linux 4.18.0-32.el8.x86_64
      Architecture: x86-64

To change hostname from linux-mig6 to suse-rhel8, enter:
$ sudo hostnamectl set-hostname nixcraft-rhel8
$ hostnamectl

Conclusion

On RHEL 8 one can use the hostnamectl command to control the system hostname and set a new name as well. This is recommended method for all RHEL 8 users.