nixpkgs.flake.setNixPath

Whether to set NIX_PATH to include nixpkgs=flake:nixpkgs such that <nixpkgs> lookups receive the version of nixpkgs that the system was built with, in concert with nixpkgs.flake.setFlakeRegistry.

This is on by default for NixOS configurations built with flakes.

This makes nix-build '<nixpkgs>' -A hello work out of the box on flake systems.

Note that this option makes the NixOS closure depend on the nixpkgs sources, which may add undesired closure size if the system will not have any nix commands run on it.