I have installed the tensorflow-gpu package, as well as all requirements for running tensorflow on the GPU.
Now I wanted to test it, so I downloaded the retrain.py script from the image retraining Tutorial (https://www.tensorflow.org/tutorials/image_retraining) and ran it with my own images (Horses in one Folder, Cars Planes and some more in Folder "unknown"), but it doesn't run on the GPU (0% usage), only on the CPU (7% usage)
GPU: Nvidia GeForce GTX 1060 6GB, Driver Version: 390.59, Cuda Version: 9.0.176
CPU: Ryzen 7 1700x
OS: Ubuntu Server 18.04