Libcuda missing

My system is Ubuntu 16.04. I want to create a virtual environment with python 2.7.12, tensorflow-GPU and ROS support. I have ROS already installed in my system. I have Cuda 9.0 installed on host PC using SDK Manager 1.4. Tensorflow-gpu 1.12.0 is compatible with Cuda 9.0, python 2.7 and gcc 4.8. I performed the following operations.

$ python2 -V
Python 2.7.12

$ gcc --version
gcc (Ubuntu 5.4.0-6ubuntu1~16.04.12) 5.4.0

I believe I also have to install gcc 4.8

$ virtualenv -p $(which python2) --system-site-packages env1
$ cd env1/binw
$ pip install msgpack argparse # installing prerequisites
$ pip install -U rosinstall empy defusedxml netifaces

when I tried to install tensorflow-gpu 1.12.0, installation failed with the following error
ERROR: Package ‘setuptools’ requires a different Python: 2.7.12 not in ‘>=3.5’

$ pip install --upgrade ‘setuptools<45.0.0’ # so downgraded setuptools
$ pip install tensorflow-gpu==1.12.0 # installation succedded

When trying to load tensorflow with a python script the following error was returned
ImportError: cannot open shared object file: No such file or directory

looking for in the following directories
but libcuda not found anywhere.

Now, is libcuda really in my system. If yes, where. If no, why SDK Manager shows “Cuda on host” installed in system. Is libcuda not installed as part of “Cuda on host”. Then how to install libcuda and what is installed in “Cuda on host” and where?

Just some more findings

$ lsmod | egrep -i ‘(nvidia|version|nouveau)’
nouveau 1712128 1
mxm_wmi 16384 1 nouveau
ttm 106496 1 nouveau
i2c_algo_bit 16384 2 i915,nouveau
drm_kms_helper 172032 2 i915,nouveau
drm 401408 15 drm_kms_helper,i915,ttm,nouveau
wmi 24576 7 intel_wmi_thunderbolt,dell_wmi,wmi_bmof,dell_smbios,dell_wmi_descriptor,mxm_wmi,nouveau
video 45056 4 dell_wmi,dell_laptop,i915,nouveau

$ dpkg -l | egrep ‘cuda-repo’
ii cuda-repo-ubuntu1604-10-2-local-10.2.89-440.33.01 1.0-1 amd64 cuda repository configuration files
ii cuda-repo-ubuntu1604-9-0-local 9.0.252-1 amd64 cuda repository configuration files