From NixOS Wiki

krops is a lightweight toolkit to deploy NixOS systems, remotely or locally.

How it works

krops does not deploy systems by itself, it is not a conventional deployment tool. It is a tool to generate scripts which then are able to deploy a system, so it can be thought of as a framework for deploying systems.

A declarative configuration can be deployed via krops without modification, only requirement is that the system that is deployed is accessible via a ssh root login.

The in-depth example by Ingolf Wagner shows how to configure krops for deploying one or multiple remote systems.