Ubuntu 14.04下消除登陆界面白点和来宾账户

消除白点：
sudo xhost +SI:localuser:lightdm
sudo su lightdm -s /bin/bash
gsettings set com.canonical.unity-greeter draw-grid false

关闭来宾账户命令：

sudo sh -c 'echo "allow-guest=false" >> /usr/share/lightdm/lightdm.conf.d/50-ubuntu.conf'
sudo service lightdm restart