Permantely change hostname of ubuntu machine

https://www.cyberciti.biz/faq/ubuntu-20-04-lts-change-hostname-permanently/ 

Ubuntu 20.04 LTS change hostname permanently

The procedure to change the computer name on Ubuntu 20.04 LTS:

1. Type the hostnamectl command :
   sudo hostnamectl set-hostname newNameHere
   Delete the old name and setup new name.
2. Next Edit the /etc/hosts file:
   sudo nano /etc/hosts
   Replace any occurrence of the existing computer name with your new hostname.
3. Reboot the system to changes take effect:
   sudo reboot