Reproducible nix-env -i with only Nix, no NixOS

Question

I am only using Nix as a package manager and not using all of NixOS. I would like a reproducible nix-env -i package installation whic

Answer 1

From Nixpkgs you can use the buildEnv function to construct symlink farms similar to how nix-env produces them.

This lets you group packages together into groups that you want to update separately. Of course a single group is perfectly valid if that suits your applications.

Here's an example greeting-tools.nix:

let
  pkgs = import <nixpkgs> {};
  inherit (pkgs) buildEnv;

in buildEnv {
  name = "greeting-tools";
  paths = [ pkgs.hello pkgs.cowsay pkgs.figlet ];
}

You can install it and remove it as follows

$ nix-env -i -f greeting-tools.nix
installing 'greeting-tools'
$ hello
Hello, world!
$ nix-env -e greeting-tools
uninstalling 'greeting-tools'
$ hello
The program ‘hello’ is currently not installed. [...]

To update your packages, you have to re-run the installation command. nix-env -u will not work correctly because that only looks at Nixpkgs, which probably doesn't have anything named like that.

An alternative may be home manager.