Fixing the legacy gpg keyring warning when installing CUDA on Ubuntu for WSL2

ubuntu-cuda-wsl2.md

Ubuntu, CUDA, WSL2 and legacy keyrings

In the Ubuntu tutorial on enabling CUDA with WSL2, and specifically in part 3, you are directed to use apt-key to point Ubuntu at the correct toolkit package. On Ubuntu 22.04 this will lead to the following warning whenever you run apt-get update:

 Key is stored in legacy trusted.gpg keyring (/etc/apt/trusted.gpg), see the DEPRECATION section in apt-key(8) for details.

To fix this, follow the instructions at Ask Ubuntu. Here are those instructions tailored for the cudatools installation:

1. List the keys

   sudo apt-key list

2. Look for the section that mentions cudatools:

   /etc/apt/trusted.gpg
   --------------------
   pub   rsa4096 2022-04-14 [SC]
         EB69 3B30 35CD 5710 E231  E123 A4B4 6996 3BF8 63CC
   uid           [ unknown] cudatools <cudatools@nvidia.com>
   

3. Export the key by taking the last 8 characters from the pub section without the space:

   sudo apt-key export 3BF863CC | sudo gpg --dearmour -o /usr/share/keyrings/nvidia.gpg

4. Edit the apt source list that points to the nvidia repo, mine was at: /etc/apt/sources.list.d/archive_uri-https_developer_download_nvidia_com_compute_cuda_repos_wsl-ubuntu_x86_64_-jammy.list. Add a [signed-by=/usr/share/keyrings/nvidia.gpg] tag to the deb entry:

   deb [signed-by=/usr/share/keyrings/nvidia.gpg] https://developer.download.nvidia.com/compute/cuda/repos/wsl-ubuntu/x86_64/ /
   

On next update, the warning will be gone.