Hjem [ˈjɛmˀ]

A streamlined way to manage your $HOME with Nix.

Synopsis
Features | Interface
Future Plans

What is this?

Hjem ("home" in Danish) is a module system that implements a simple and streamlined way to manage files in your $HOME, such as but not limited to files in your ~/.config. Hjem aims to approach as an alternative, easy-to-grasp utility for managing your $HOME purely and safely.

Features

We have learned from the mistakes made in the ecosystem.

1. Powerful $HOME management functionality and potential
2. Small and simple codebase with minimal abstraction
3. Robust, safe and manfiest based file handling with smfh
4. Multi-user by design, works with any number of users
5. Designed for ease of extensibility and integration

No compromises, only comfort.

Implementation

Hjem exposes a very basic interface with multi-tenant capabilities, which you may use to manage individual users' homes by leveraging the module system.

{
  hjem.users = {
    alice.files = {
      # Write a text file in `/homes/alice/.config/foo`
      # with the contents bar
      ".config/foo".text = "bar";

      # Alternatively, create the file source using a writer.
      # This can be used to generate config files with various
      # formats expected by different programs.
      ".config/bar".source = pkgs.writeTextFile "file-foo" "file contents";

      # You can also use generators to transform Nix values
      ".config/baz" = {
        # Works with `pkgs.formats` too!
        generator = lib.generators.toJSON { };
        value = {
          some = "contents";
        };
      };
    };
  };
}

Note

Each attribute under hjem.users, e.g., hjem.users.alice or hjem.users.jane represent a user managed via users.users in NixOS. If a user does not exist, then Hjem will refuse to manage their $HOME by filtering non-existent users in file creation.

Module Interface

The interface for the homes module is conceptually very similar to prior art (e.g., Home Manager), but it does not act as a collection of modules like Home Manager. Instead, we only implement basic features, and leave abstraction to the user to do as they see fit. This, of course, does not mean that a module collection cannot exist. In fact, one already does!

Below is a live implementation of the module.

nix-repl> :p nixosConfigurations."nixos".config.hjem.users
{
  alice = {
    # Whether to overwrite target files if they exist
    clobberFiles = false;
    directory = "/home/alice";
    enable = true;
    environment = {
      # A loadable script to prepare shell environments
      loadEnv = «derivation /nix/store/gvbjmalyxl4jd0i4paz6nnhvszg01823-load-env.drv»;
      sessionVariables = { };
    };
    files = {
      ".config/foo" = {
        clobber = false;
        enable = true;
        executable = false;
        relativeTo = "/home/alice";
        source = «derivation /nix/store/lwrnp6js4925kfzybrcyvx4m7gilq02w-config-foo.drv»;
        target = "/home/alice/.config/foo";
        text = "Hello world!";
      };
    };
    packages = [ ];
    user = "alice";
  };
}

Linker Implementation

Hjem relies on our home-baked tool smfh, an atomic and reliable file creation tool designed by Gerg-l. We utilize smfh and Systemd services ¹ to correctly link files into place.

Environment Management

Hjem does not manage user environments as one might expect, but it provides a convenient environment.sessionVariables option that you can use to store your variables. This script will be used to store your environment variables in a POSIX-compliant script generated by Hjem, which you can source in your shell configurations.

Things to do

Hjem is mostly feature-complete, in the sense that it is a clean implementation of home.files in Home Manager: it was never a goal to dive into abstracting files into modules.

Alternative or/and configurable file linking mechanisms

Hjem previously utilized systemd-tmpfiles to ensure files are linked in place. This has served us well for the short duration that we relied on them, but we have ultimately decided to go with our in-house file linker developed by Gerg-l. The new linker is, of course, infinitely more powerful and while we are not looking back, we understand that some users might be interested in alternative linking mechanisms that they can customize as they prefer.

Tip

Setting hjem.linker to null will use systemd-tmpfiles as the linker backend. You may give this option a package you've created to use it as your linker, but it must be fully compatible with the interface smfh currently supports.

Alternatively, similar to how NixOS handles external bootloaders, we may consider a rebuild "hook" for allowing alternative linking methods where the module system exposes the files configuration to a package user provides.

Attributions / Prior Art

Special thanks to Nixpkgs and Home Manager. The interface of the hjem.users module is inspired by Home Manager's home.file and Nixpkgs' users.users modules. What is now Hjem started as an experimental module addition to Nixpkgs' users.users. Hjem would not be possible without any of those projects, thank you!

A project worthy of note is Hjem-Rum, by @Lunarnovaa and @nezia1, which establishes a Home Manager-like module system for users less comfortable with manually linking files in place. If you wish to utilize the power of Hjem, but want an easier interface, we encourage you to take a look at Hjem Rum.

Last but not least, our sincerest thanks to everyone who has used, contributed to or just talked about Hjem in public spaces. Thank you for the support!

License

This project is made available under Mozilla Public License (MPL) version 2.0. See LICENSE for more details on the exact conditions. An online copy is provided here.

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1. Which is preferable to hacky activation scripts that may or may not break. Systemd services allow for ordered dependency management across all services, and easy monitoring of Hjem-related services from the central systemctl interface. ↩︎