TensorFlow 1.5 RC supports CUDA 9.0 (not 9.1)

If you've just done a dnf update to get the kernel version that has the fixes for Meltdown and Spectre, you may have inadvertently pulled in CUDA 9.1 as well. This isn't supported yet in TF-nightly-gpu unless you install from source (which is difficult if using the Negativo CUDA repos).

This quick note explains how to downgrade to a supported CUDA version

Check the CUDA version installed

rpm -qa | grep cuda-devel
#cuda-devel-9.1.xxxx

Find the CUDA versions installable

As root :

dnf repoquery cuda-devel
#cuda-devel-1:9.0.176-2.fc27.x86_64
#cuda-devel-1:9.1.85-1.fc27.x86_64
#cuda-devel-1:9.1.85-2.fc27.x86_64

Downgrade to a 9.0 CUDA version

Using one of the versions listed above that is 9.0.xxx, as root :

dnf downgrade cuda-1:9.0.176-2.fc27.x86_64

This should downgrade all the dependencies too - making the system whole again.

All Done!