You can also install CUDA directly from the offline installer, but this is a little easier.
sudo apt update
sudo apt upgrade -y
mkdir install ; cd install
wget https://developer.download.nvidia.com/compute/cuda/repos/ubuntu1804/x86_64/cuda-ubuntu1804.pin
sudo mv cuda-ubuntu1804.pin /etc/apt/preferences.d/cuda-repository-pin-600
sudo apt-key adv --fetch-keys https://developer.download.nvidia.com/compute/cuda/repos/ubuntu1804/x86_64/7fa2af80.pub
sudo add-apt-repository "deb http://developer.download.nvidia.com/compute/cuda/repos/ubuntu1804/x86_64/ /"
sudo apt-get update
sudo apt-get -y install cuda-10-2
Download CuDNN here (BOTH the runtime and dev, deb) from: https://developer.nvidia.com/rdp/cudnn-download
sudo dpkg -i libcudnn7_7.6.5.32-1+cuda10.2_amd64.deb
sudo dpkg -i libcudnn7-dev_7.6.5.32-1+cuda10.2_amd64.deb
This method of installation installs cuda in /usr/include and /usr/lib/cuda/lib64, hence the file you need to look at is in /usr/include/cudnn.h.
cat /usr/include/x86_64-linux-gnu/cudnn_v*.h | grep CUDNN_MAJOR -A 2
Step 3: Installing TensorRT (~2 minutes)
Download TensorRT here. Use version 7.0.
sudo dpkg -i nv-tensorrt-repo-ubuntu1804-cuda10.2-trt7.0.0.11-ga-20191216_1-1_amd64.deb
sudo apt update
sudo apt install tensorrt libnvinfer7
export CUDA_HOME=/usr/local/cuda
export DYLD_LIBRARY_PATH=$CUDA_HOME/lib64:$DYLD_LIBRARY_PATH
export PATH=$CUDA_HOME/bin:$PATH
export C_INCLUDE_PATH=$CUDA_HOME/include:$C_INCLUDE_PATH
export CPLUS_INCLUDE_PATH=$CUDA_HOME/include:$CPLUS_INCLUDE_PATH
export LD_LIBRARY_PATH=$CUDA_HOME/lib64:$LD_LIBRARY_PATH
export LD_RUN_PATH=$CUDA_HOME/lib64:$LD_RUN_PATH
https://stackoverflow.com/questions/64051293/tensorflow-2-3-and-libcublas-so-10
When installing 10.1 created two libs; 10.1 and 10.2, the app cannot find libcublas. Use the above method to resolve (answered by nobilearn)