If your build is failing during an 'apt-get update' command with the following error...
Reading package lists... Done
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.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
...you have run in to a known issue that occurred due to an expiration of the nvidia gpg key.
A new key is available and can be installed in your build with the following process. Take note of the inline comments as they are important.
#fix nvidia gpg key
#The following files may not exist in your environment and the commands will fail the build if they don't,
#so comment out the next two lines as needed
sudo rm /etc/apt/sources.list.d/cuda.list && \
sudo rm /etc/apt/sources.list.d/nvidia-ml.list && \
#The ubuntu version in the URL below is important, note this example is for Ubuntu 18.04.
#You can find your ubuntu version with the command in a workspace terminal.
#Update the URL as per the following nvidia article
wget https://developer.download.nvidia.com/compute/cuda/repos/ubuntu1804/x86_64/cuda-keyring_1.0-1_all.deb && \
sudo apt-key del 7fa2af80 && \
sudo dpkg -i cuda-keyring_1.0-1_all.deb
NOTE: when adding the additional instructions make sure the new RUN commands are executed prior to any other update operations (apt or yum), otherwise the run will fail .