Max concurrent jobs / cpu cores for nix build

[onny]

I'm running

NIX_BUILD_MAX_JOBS=12 NIX_BUILD_CORES=8 NIXPKGS_ALLOW_UNSUPPORTED_SYSTEM=1 NIXPKGS_ALLOW_INSECURE=1 NIX_PATH=nixpkgs=/home/onny/nixpkgs QEMU_NET_OPTS="hostfwd=tcp::8080-:80" nixos-shell --guest-system riscv64-linux vm-oncall.nix --show-trace

on a nix community builder but nix build only runs at one build job very slow and does not build and parallel.

Do I miss some setting or argument?

[Mic92]

Not quite sure what the issue is. You could try bash -x $(command -v nixos-shell), it should give you the underlying nix-build command.