Ubuntu input SU hint authentication failure resolution method

Start Apache service unexpectedly prompt permission is not enough, with SU switch, enter password hint authentication failed, this is done, and then once the original Ubuntu installed, root user is locked, not allowed to log in, and do not allow Su to root, For desktop users this may be to enhance security, but the server version of this is not true, and quickly set it down.

Under Terminal

[email protected]: ~$ sudo passwd

Password: <---Enter the password for the user at the time of installation

Enter New UNIX Password: <---The new root user password

Retype new UNIX Password: <---Repeat the root user password

passwd: Password has been successfully updated

Ubuntu input SU hint authentication failure resolution method