NVIDIA-SMI has failed because it couldn‘t communicate with the NVIDIA driver.

参考：https://zhuanlan.zhihu.com/p/89714824

用 nvidia-smi 查看一下，提示如下错误：

NVIDIA-SMI has failed because it couldn't communicate with the NVIDIA driver. 
Make sure that the latest NVIDIA driver is installed and running.

又用 nvcc -V 看了一下驱动还在，网上搜了一下，用下面的方法顺利解决了问题 ，参考：https://blog.csdn.net/hangzuxi8764/article/details/86572093

sudo apt install dkms
sudo dkms install -m nvidia -v 418.87.00

其中，418.87.00 是之前安装 nvidia 驱动的版本号，可通过下面方法查到：

ls /usr/src | grep nvidia

如果安装过程出现错误，可能是gcc版本不对，需要切换版本，比如nvidia-450就需要gcc7，gcc5安装会出错