It depends on what you mean. If setting up a development machine (i.e non-server) there is the home-manager package which on top of the system configures users

It depends on what you mean. If setting up a development machine (i.e non-server) there is the home-manager package which on top of the system configures users (what packages they have, home folder content). Secondly, for an exactly deterministic install you'd also pin the nixpkgs to some commit (the package repository is a git repo). But I guess many don't do this unless they have specific needs.