One: Solve the root login of Kylin users.
First, after the self-built user logs in, enter the command "sudo -i" in the terminal, enter the current user password to enter root, and then use "passwd root" to reset the root password.
Second, create /etc/lightdm/lightdm.conf with the following content:
[Seat:*]
greeter-show-manual-login=true
allow-guest=false
After saving and restarting the operating system, you will find that there is an additional "login" item in the welcome interface. Click the login item to enter root and password to log in.
2: Solve the problem that there is no volume icon for Kylin users after logging in as root
Enter the file of this path: "vi /root/.profile"
Add this line to the file: "pulseaudio --start --log-target=syslog"
Restart to see the volume icon.