以root身份在本机登录失败，提示如下：
/etc/X11/gdm/PreSession/Default:Registering your session with wtmp and utmp
/etc/X11/gdm/PreSession/Default:runing:/usr/bin/X11/sessreg -a -w /var/log/wtmp -u /var/run/utmp -x "/var/gdm//:0.Xservers" -h " " -l:0 " "root"
(gnome-session:4831):Gtk-WARNING ** :Cannot open display:
请高人帮助解决！
