[Question] Flakes on a non NixOS system

EdenEast commented 4 years ago

I have been looking for a way to convert my dotfiles repository over to nix and found home-manager to be a great way to accomplish this. My current dotfiles repository has the issue of supporting multiple different environments linux, wsl2, and windows. I would like to take advantage of flakes to create multiple flake outputs that I can build depending on where I am. I have not been able to find a way to create a flake file that does not depend on some nixos system dependencies.

I know that you can do something like this with nixos, Is there something similar you can do with just home-manager?

# flake.nix
{
  inputs = {
    # ...
  };

  outputs = {
    nixosConfigurations = {
      machine = lib.nixosSystem {
        system = "x86_64-linux";
        modules = [
          # ...
        ];
      };
    };

    machine = inputs.self.nixosConfigurations.machine.config.system.build.toplevel;
  };
}

nix build .#machine

cole-h commented 4 years ago

I believe that's what https://github.com/nix-community/home-manager/blob/9b1b55ba0264a55add4b7b4e022bdc2832b531f6/flake.nix#L10 is intended for, maybe? I've never actually used it, since I am on NixOS, but you might want to give it a shot and experiment.

bnjmnt4n commented 3 years ago

Did anyone ever successfully manage to get a working example of home-manager using flakes on a non-NixOS system? I'm pretty new to Nix and flakes, so I don't have much experience with this, but I will look into it and experiment soon.

cole-h commented 3 years ago

I think flakes on non-NixOS would require support in the home-manager script / tool. One could look to nixos-rebuild's flake support to draw inspiration, but I don't know how well it would translate.

mjlbach commented 3 years ago

This thread has a couple different approaches https://discourse.nixos.org/t/example-use-nix-flakes-with-home-manager-on-non-nixos-systems/10185

EdenEast commented 3 years ago

I have been able to get something working for my configuration a base example would be something like this

# flake.nix
{
  description = "Example home-manager from non-nixos system";
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
    home-manager = {
      url = "github:nix-community/home-manager/master";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };

  outputs = { self, ... }@inputs: {
    homeConfigurations = {
      wsl = inputs.home-manager.lib.homeManagerConfiguration {
        configuration = ./home/hosts/wsl.nix;
        system = "x86_64-linux";
        homeDirectory = "/home/user";
        username = "user";
      };
    };

    wsl = self.homeConfigurations.wsl.activationPackage;
    defaultPackage.x86_64-linux = self.wsl;
  };
}

nix build .#wsl

For my personal configuration I have modeled it based on @davidtwco excellent configuration. His configuration is well structured and easy to understand. You can also look at my current work in progress configuration

TLATER commented 3 years ago

I suppose a home-manager switch --flake '.#' with a little bit of additional magic to assign the correct configuration from the flake path is all that's missing to make the above a little more user friendly?

Currently you need to manually run ./result/activate, and of course set the correct hostname, which isn't as ergonomic as it used to be.

terlar commented 3 years ago

I currently have a shell script that I add to the flakes devShell, then I hook up the devShell with direnv so I upon entering the project I will get it on my path. All I have to do is to run switch-home.

Here is the script: https://github.com/terlar/nix-config/blob/570134ba7007f68e058855e0d6a1677a9dc3fa27/lib/scripts.nix#L11-L29

  switchHome = writeShellScriptBin "switch-home" ''
    set -euo pipefail
    export PATH=${lib.makeBinPath [ gitMinimal jq nixUnstable ]}
    usr="''${1:-$USER}"

    1>&2 echo "Switching Home Manager configuration for: $usr"

    usrExists="$(nix eval --json .#homeManagerConfigurations --apply 'x: (builtins.any (n: n == "'$usr'") (builtins.attrNames x))' 2>/dev/null)"

    if [ "$usrExists" != "true" ]; then
      1>&2 echo "No configuration found, aborting..."
      exit 1
    fi

    1>&2 echo "Building configuration..."
    out="$(nix build --json ".#homeManagerConfigurations.$usr.activationPackage" | jq -r .[].outputs.out)"
    1>&2 echo "Activating configuration..."
    "$out"/activate
  '';

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terlar commented 3 years ago

With the latest changes to flakes you can now do this:

{
  description = "Example flake for generic Linux Home Manager usage";

  inputs = {
    home-manager.url = "github:nix-community/home-manager";
  };

  outputs = { self, nixpkgs, home-manager, ... }: {
      apps.x86_64-linux.home-manager = {
        type = "app";
        program = "${home-manager.defaultPackage.x86_64-linux}/bin/home-manager";
      };

      homeConfigurations = {
        my-user = home-manager.lib.homeManagerConfiguration {
          # your config here ...
        };
      };
    };
}

Then you can run:

nix run .#home-manager -- switch --flake .

To switch to your my-user if that is your current user. It will also try $USER@hostname if you have configuration named like that. If you want to switch to a specific config just replace the . with .#nameOfConfig.

If you have Home Manager installed as a package you can run home-manager switch --flake . instead.

Another alternative to nix run is to add the package home-manager to a devShell, then you could run the home-manager command from there.