Note this turorial begins on an Xubuntu 18.04.1 system after a fresh install and I made the error of installing the latest Nvidia Drivers (415) and hashcat from the repositories. I got the error message “Cannot find an OpenCL ICD loader library.” when trying to run hashcat. This is what I did to get it to work so hopefully it will be helpful to others.
If you haven’t already don’t install the nvidia drivers from the Ubuntu repositories. Directions on that can be found here but I stress that you should not follow them if you have version 18.04.
1. Boot as normal and get to login screen (or desktop if you autologin).
2. Download the latest CUDA for your system at https://developer.nvidia.com/cuda-downloads?target_os=Linux. As of the creation of this tutorial the file will be cuda_10.0.130_410.48_linux.run.
3. Press the key combination Ctrl + Alt + F1 to exit out of the GUI. Authenticate with your username and password.
4. type sudo service lightdm stop and press Enter to stop X11 (desktop GUI).
5. type sudo apt-get remove --purge nvidia* and press Enter to purge all nvidia items.
6. type sudo find / -name libOpenCL\* -print0 | xargs -0 rm -rf to find and puge all libOpenCL files
7. Reboot
8. Boot as normal and get to login screen (or desktop if you autologin). Note: your GUI may not look as clean as you would like. No worries just keep going with this tutorial.
9. Press the key combination Ctrl + Alt + F1 to exit out of the GUI. Authenticate with your username and password.
10. Change directory to your Downloads folder or whereever you saved cuda_10.0.130_410.48_linux.run
11. Make the file executable and run it. Follow all prompts for installation.
12. Reboot and you should be all set.
References
http://www.linuxandubuntu.com/home/how-to-install-latest-nvidia-drivers-in-linux
https://devtalk.nvidia.com/default/topic/1036967/linux/unable-to-use-opencl-cuda-on-ubuntu-18-04/
