Go Ubuntu defaults to login with the root user and avoids entering the password

Enable Root User Login

Ctrl + Alt + t Enter the terminal, enter cd /usr/share/lightm/ightm.conf.d , if you are prompted to do not have that file or directory. Then go into the catalogue again and again.
Several files that you will see after you enter.
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Enter the command to vi 50-unity-greeter.conf add:

1. greeter-show-manual-login=true
2. allow-guest=false

At this point, you can log in with the root user, enter the username root, and the root user's password to login. If you do not want to enable root user login, then greeter-show-manual-login=true change the true to false.

Avoid entering a password to log in directly

Root User login is enabled above. Now, if you are logged in, you are not prompted to enter your account password.
Enter the terminal input cd /etc/lightdm after entering the directory, input the vi lightdm.conf file for editing, paste the following statement:

1. [Seat:*]
2. autologin-guest=false
3. autologin-user=root
4. autologin-user-timeout=0

autologin-user=rootThis is where you set up a username that requires a password-free login, or it can be set to a non-root user.
This can also be done in a graphical interface. Steps: System Settings-user account--turn on automatic login

Off topic:
With the above settings, we will set the root user to the default login account, although the default root login is enabled, but it is not recommended to log in as the default user for the root user. When you need to use root privileges, you can add the command before sudo , or enter su or su root or sudo -i temporarily switch to root login in the terminal before entering the command.

I ubuntu version: 15.10
Reference: http://www.ubuntukylin.com/ukylin/forum.php?mod=viewthread&tid=8445

Go Ubuntu defaults to login with the root user and avoids entering the password