[gpu] NVIDIA-SMI has failed because it couldn't communicate with the NVIDIA driver

Solved the problem by re-installing CUDA:

wget https://developer.download.nvidia.com/compute/cuda/repos/ubuntu1804/x86_64/cuda-ubuntu1804.pin
mv cuda-ubuntu1804.pin /etc/apt/preferences.d/cuda-repository-pin-600
wget https://developer.download.nvidia.com/compute/cuda/11.1.0/local_installers/cuda-repo-ubuntu1804-11-1-local_11.1.0-455.23.05-1_amd64.deb
echo "md5sum: $(md5sum cuda-repo-ubuntu1804-11-1-local_11.1.0-455.23.05-1_amd64.deb)"
echo "correct: 056de5e03444cce506202f50967b0016"
dpkg -i cuda-repo-ubuntu1804-11-1-local_11.1.0-455.23.05-1_amd64.deb
apt-key add /var/cuda-repo-ubuntu1804-11-1-local/7fa2af80.pub
apt-get -qq update
apt-get -qq -y install cuda
rm cuda-repo-ubuntu1804-11-1-local_11.1.0-455.23.05-1_amd64.deb