我无法登录 GUI，输入密码后它会闪烁并返回登录 GUI，这是我的/var/log/lightdm/x-0-greeter.log文件中的内容：
** (lightdm-gtk-greeter:2893): WARNING **: Error retrieving accessibility bus address:
org.freedesktop.DBus.Error.ServiceUnknown: The name org.a11y.Bus was not provided by any .service files
** (lightdm-gtk-greeter:2893): WARNING **: Failed to load user image:
Failed to open file '/home/liao/.face': No such file or directory
因为不但一个用户无法登录，guest用户也无法登录。我的lubuntu版本：Linux ubuntu 3.16.0-31-generic #41-Ubuntu