Ubuntu input SU command shows authentication failure resolution

Because the Ubuntu system does not activate the root user by default, it needs to be activated manually:

Under Terminal input:

sudo passwd

Password: Your current password

Enter New UNIX Password: This is the root password
Retype new UNIX Password: duplicate root password

can be successful.

Note: Using Su and sudo is different, using the SU Switch user needs to enter the user's password to switch to, while using sudo is the current user's password.

Ubuntu input SU command shows authentication failure resolution