The system will automatically pull a cachix.nix at the root if one exists. This is usually created automatically by a sudo cachix use. If you're more inclined to keep the root clean, you can drop any generated files in the cachix directory into the profiles/cachix directory without further modification.

For example, to add your own cache, assuming the template lives in /etc/nixos, by simply running sudo cachix use yourcache. Then, optionally, move cachix/yourcache.nix to profiles/cachix/yourcache.nix

These caches are only added to the system after a nixos-rebuild switch, so it is recommended to call cachix use nrdxp before the initial deployment, as it will save a lot of build time.

In the future, users will be able to skip this step once the ability to define the nix.conf within the flake is fully fleshed out upstream.