Comment by raboof

For NixOS, it's in the 'how did we reproduce' section of the article: the last step of that process produces the iso in the ./result/iso directory.

It sounds like what you're looking for is the commands that that build invoked, but I'm not sure what step you're looking for. For example, the xorriso invocations are at https://github.com/NixOS/nixpkgs/blob/master/nixos/lib/make-...