You can use the
sudo command in the Terminal app to execute commands as a different user, such as the root user. After you enter the command, Terminal asks you to enter your password. If you enter the wrong password or a blank password, the command isn't executed.
If you're using an administrator account that doesn't have a password, add a password to your admin account in Users & Groups preferences. You should then be able to execute
sudo commands in Terminal. Remember, Terminal doesn't show your password you type it. If you enter the wrong password, Terminal asks you to try again.