nix why-depends

Show why a package depends on another package. More information: https://nixos.org/manual/nix/stable/command-ref/new-cli/nix3-why-depends.html.

• Show why the currently running NixOS system requires a certain store path:

nix why-depends {{/run/current-system}} {{/nix/store/...}}

• Show why a package from nixpkgs requires another package as a build-time dependency:

nix why-depends --derivation {{nixpkgs#dependent}} {{nixpkgs#dependency}}