A hostname is a unique identifier that is assigned to a device (host) connected to the network. It can distinguish one device from another on a specific network. This tutorial shows how to change hostname in the Linux. Provided method doesn't require rebooting system.
Assign new hostname to variable:
sed command to find the line that contains 127.0.1.1 IP address and replace the old hostname with the new one.
sudo sed -i -e "s/127.0.1.1.*/127.0.1.1 $NEW_HOSTNAME/" /etc/hosts
hostnamectl command to change hostname:
sudo hostnamectl set-hostname $NEW_HOSTNAME
To change hostname in Bash prompt of currently logged user, switch to current user:
sudo su - $USER