Example of reproducible deployments using nix-shell and nixops

default.nix

{
  server = {
    deployment.targetHost = "target.host.com";
    services.openssh.enable = true;
  };
}

shell.nix

let
  # Use a specific version of nixpkgs:
  pkgsSrc = builtins.fetchTarball {
    url = https://github.com/nixos/nixpkgs-channels/archive/19879836d10f64a10658d1e2a84fc54b090e2087.tar.gz;
    sha256 = "f01e3a617e5b1d3c2ee8e525f3a48d1c4402d7c47f5cbf772c48ff57056481f4";
  };
  
  # Use a local version of nixpkgs:
  # pkgsSrc = ./nixpkgs;

  pkgs = (import pkgsSrc {});
in
pkgs.stdenv.mkDerivation rec {
  name = "nixops-env";
  buildInputs = with pkgs; [ awscli pkgs.nixops ];
  shellHook = ''
    [ -f ~/.aws/vars ] && . ~/.aws/vars
    export NIX_PATH=${pkgs.path}:nixpkgs=${pkgs.path}:.
  '';
}

This can run using:

nix-shell --run "nixops deploy"