I just installed GTX 970 into my Ubuntu box. Using the following command shows the card is connected to the system.

~$ lspci -nnk |grep NVIDIA 60:00.0 VGA compatible controller [0300]: NVIDIA Corporation GM204 [GeForce GTX 970] [10de:13c2] (rev a1) 60:00.1 Audio device [0403]: NVIDIA Corporation GM204 High Definition Audio Controller [10de:0fbb] (rev a1)

But when I ran my Keras script using TensorFlow as the backend, it didn't seem to speed up the training - each epoch still takes a long time to run.

Is there any way to check if Keras is using GPUs?

You need to install the cuda lib for tensorflow to use GPUhttps://www.tensorflow.org/get_started/os_setup#test_the_tensorflow_installation

If it is installed correctly, everytime you run tf or keras with tf backend, it will show something like "using Cuda library..."