Ubuntu12.04 start the root user and set the root password in two ways

Ubuntu12.04 start the root user and set the root password in either of the following ways: 1 sudo passwd root and then enter the new password twice. However, I encountered a new system. After reboot, the system prompts a wrong password upon Logon: invlid password and please try again. I found that I had to modify it in "single user mode. When starting Ubuntu12.04, press the shift key to go to grub. We recommend that you move the cursor to "recovery mode"/"recovery mode" and press the e key to go to the command line. Change "ro recovery nomodeset" to "rw single init =/bin/bash" and press "ctrl + x" to enter the shell of a single user, and then 1 passwd root to reset the root password. For the root startup option, you can follow the following operations: 1vi/etc/lightdm. conf to append this sentence: 1greeter-show-manual-login = true restart to see the effect.