reset root password ubuntu 20.04 code example

Example 1: set password to root ubuntu 20.04

$ sudo -i
$ passwd root
new password:...
confirm password:...

Example 2: default root password ubuntu 18.04

$ sudo passwd

Example 3: change password ubuntu 20.04

open your terminal
ctrl-alt-t

passwd username

If you have admin password you can change all passwd of users 
su -
passwd username