Change the directory to store docker images

https://stackoverflow.com/a/49743270/7057866

Ubuntu 20.04 image asks to set timezone interactively

A great example where DEBIAN_FRONTEND=noninteractive does its job. https://anonoz.github.io/tech/2020/04/24/docker-build-stuck-tzdata.html

W: GPG error: https://developer.download.nvidia.com/compute/cuda/repos/ubuntu1804/x86_64  InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY A4B469963BF863CC
E: The repository 'https://developer.download.nvidia.com/compute/cuda/repos/ubuntu1804/x86_64  InRelease' is not signed.

This often happens when I use cudagl base image... NVIDIA recognizes this problem: https://forums.developer.nvidia.com/t/18-04-cuda-docker-image-is-broken/212892/7

You can just add these lines (for Ubuntu18.04)

RUN apt-key del 7fa2af80
RUN apt-key adv --fetch-keys https://developer.download.nvidia.com/compute/cuda/repos/ubuntu1804/x86_64/3bf863cc.pub
RUN apt-key adv --fetch-keys https://developer.download.nvidia.com/compute/machine-learning/repos/ubuntu1804/x86_64/7fa2af80.pub