Update hostname on an Ubuntu machine

tl;dr

use the hostnamectl command on Ubuntu (and other Systemd based distros)

1hostnamectl set-hostname new.hostname.com

1# TEMPORARILY update hostname, will reset on reboot, will need a new Terminal to see the change
2hostname my.newHostname.com

1# make a more permanent change by updating `/etc/hosts` and `/etc/hostname` files
2sudo nano /etc/hostname
3sudo nano /etc/hosts
4sudo reboot

1# use the `hostnamectl` command
2hostnamectl set-hostname new.hostname.com

1hostnamectl

   Static hostname: new.mydomain.com
         Icon name: computer-vm
           Chassis: vm
        Machine ID: 23f62493fbfe41359cc6b4f409570ac1
           Boot ID: 6916c2a8a1e049bda00ed12a189d90dd
    Virtualization: xen
  Operating System: Ubuntu 18.04.1 LTS
            Kernel: Linux 4.15.0-1021-aws
      Architecture: x86-64