extra-sandbox-paths works on CLI but fails in config

[rtburns-jpl]

Describe the bug

I'm trying to build packages with cuda support on non-NixOS, and run tests during the nix-build. This requires exposing nvidia GPU devices such as /dev/nvidia0 to the check phase, which I'm trying to achieve with extra-sandbox-paths. Oddly, specifying --option extra-sandbox-paths ... works on the command-line, but fails when I specify the same option in ~/.config/nix/nix.conf:

error: while setting up the build environment: getting attributes of path '"/dev/nvidia0"': No such file or directory

Steps To Reproduce

• Works: nix-build '<nixpkgs>' -A hello --check --option extra-sandbox-paths "/dev/tty0"
• Fails: nix-build '<nixpkgs>' -A hello --check with ~/.config/nix/nix.conf containing
  extra-sandbox-paths = "/dev/tty0"
error: while setting up the build environment: getting attributes of path '"/dev/tty0"': No such file or directory

nix-env --version output
nix-env (Nix) 2.3.10

[stale]

I marked this as stale due to inactivity. → More info

[vobloeb]

Don't you expose /run/opengl-driver too for access to libcuda.so ?

[rtburns-jpl]

Yes, and I was running into the same issue trying to add /run/opengl-driver to extra-sandbox-paths. However, I'm not able to reproduce this anymore, even though I'm still using the same nix version. So I'll close this pending a reliable reproducer for this issue.

[vobloeb]

I reproduce.
To pass CUDA tests I have to run

nix-build --option extra-sandbox-paths '/dev/nvidiactl /dev/nvidia-uvm /dev/nvidia0 /run/opengl-driver=/nix/store/2kb9a8rdac7gn1m6phk4sz9kg6rl7vsm-nvidia-x11-470.57.02-5.4.134

where /nix/store/2kb9a8rdac7gn1m6phk4sz9kg6rl7vsm-nvidia-x11-470.57.02-5.4.134 is config.boot.kernelPackages.nvidia_x11

That's why using /etc/nix/nix.conf would be more convenient, I could generate it using

nix.sandboxPaths = [
  "/dev/nvidiactl"
  "/dev/nvidia-uvm"
  "/dev/nvidia0"
  "/run/opengl-driver=${config.boot.kernelPackages.nvidia_x11}"
];

but it does not work
only command-line works

[vobloeb]

Well, sudo systemctl restart nix-daemon does solve it.
nix-daemon does not reread /etc/nix/nix.conf on change

[rtburns-jpl]

Well, I still can't reproduce the original error: while setting up the build environment: getting attributes of path '"/dev/nvidia0"': No such file or directory

I get the same behavior as you, where changes to /etc/nix/nix.conf aren't detected until the daemon is restarted. So I'll consider this resolved