## Usage > **Note** > Currently, `nix-weather` only has first-class support for flakes. General usage would be like this: ```bash nix-weather --name myhost --config ~/git/my-nixos-config ``` Here, we specify the name of the host, as specified at the flake output `nixosConfiguration`, and a path to the NixOS configuration flake. ## How It Works The basic idea is that we construct a set of all requisites to build the top-level of a NixOS configuration, and then query Nix cache(s) for the narinfo. By doing this in a high concurrency, parallel task runner (i.e. tokio async runtime), and only querying the headers for status codes, we can reach impressive speeds, typically around 45~ network time. One of the biggest limiting factors regarding speed is building the `config.system.toplevel`, and finding the necessary requisites with `nix-store`. Caching the requisites is a future goal, so that we only have to build the `toplevel`, and then match against its derivation in cache, which should cut down the nix part of the runtime by ~80%.