1.Ubuntu18.04在安裝lightdm之后重啟后出現黑屏，光標左上角閃爍
2.nvidia-smi顯示NVIDIA-SMI has failed because it couldn't communicate with the NVIDIA driver. Make sure that the latest NVIDIA driver is installed and running.
3.重裝顯卡驅動然后重新進入桌面就行了
sudo sh NVIDIA-Linux-x86_64-440.100.run
完成重裝后成功解決
最后重新進入圖形界面即可
sudo init 3
sudo init 5
注：如果無法自動遠程連接上ubuntu系統，可以通過ubuntu grub進入recover mode，在recover menu中選擇root：Drop to root shell prompt，然后通過shell命令運行顯卡驅動程序，重裝顯卡驅動
