Replace home-manager

2024-05-21

You may really don't need it

Intro

home-manager is a basic system for managing a user environment using Nix. It allows setting declarative user envs.

For a nixos user includes me, home-manager may already introduced at the same time as the config created, for managing user-spec configs. But it has really poor maintainence and code quality, and it does produced few bugs several months I use it. And I do considered removing it but seems there's no a better solution exist.

Things changed when I saw this post. TLDR:

Use nix profile mechanism instead of home.packages. User-spec package management solved.
Use nix run and nix app (flake) mechanism for deploying user-spec software configs. This could be conveniently migrate from existing home-manager profile.

The blog above doesn't gave a detail implementation for referencing, which we'll discuss here.

Before start,

Follow this post you could finally get:

rm home-manager
User specific software config switch timecost reducing, significantly.
- use home-manager as nixos module will require priviledge when trying change user settings, and consume same eval time as entire nixos config, which about 20s. Time cost reduced to ~4s after this.
Better maintainence for config. If ur powerful enough.

What we'll lost

No more home-manager. Things may not be better.
Difficulties for calling OS config option in user specific config. In home-manager with nixosModule installation (standalone install has no this function as well btw) you generally do this by calling osConfig.
slate-symlink cleaning. Which could be easily solved by writting a simple script.

Prerequisites

A Nix Flake, with a working nixosConfiguration.
(optional) A home-manager config (either standalone or nixosModule installation)
Want, to get rid of the home-manager.
About 3 hours or days.

Start with user-spec config

"

Difference between user-specific packages/config and global's: they were stored under user home.

You can always start from install user specific package

Collect Configs (Optional)

If you already have a deployed home-manager configuration, which linked things to your $HOME/.config directory, you may want to use this script to collect them all.

import os
import shutil

def find_and_copy_symlinks(source_dir, target_dir):
    """
    Recursively find all symbolic links in source_dir and copy their real files to target_dir,
    preserving the original directory structure.

    Args:
        source_dir (str): The directory to search for symbolic links.
        target_dir (str): The directory where the real files will be copied.
    """
    for root, dirs, files in os.walk(source_dir):
        for name in files + dirs:
            path = os.path.join(root, name)
            if os.path.islink(path):
                real_path = os.path.realpath(path)
                relative_path = os.path.relpath(path, source_dir)
                target_path = os.path.join(target_dir, relative_path)

                # Create directories in target path
                os.makedirs(os.path.dirname(target_path), exist_ok=True)

                # Copy the real file to the target path
                if os.path.isfile(real_path):
                    shutil.copy2(real_path, target_path)
                elif os.path.isdir(real_path):
                    shutil.copytree(real_path, target_path, dirs_exist_ok=True)

                print(f"Copied {real_path} to {target_path}")

if __name__ == "__main__":
    source_directory = f'{os.environ["HOME"]}/.config'  # Replace with the source directory
    target_directory = "./target"  # Replace with the target directory
    find_and_copy_symlinks(source_directory, target_directory)

This will collect all symlink real paths into the ./target directory. Please note that you will still need to manually replace the /nix/store/xxhash-name strings in each file.

Here’s an example of what it collected for me:

~/Src/hmlink/target
> tree
.
├── alacritty
│   └── alacritty.toml
├── aria2
│   └── aria2.conf
├── atuin
│   └── config.toml
├── bspwm
.....<snip>

Mapping target path & real file

We need to automatically build an attrset from the tree above. e.g.

{
  "/home/user/.config/alacritty/alacritty.toml" = abs_path_of_dir/alacritty/alacritty.toml;
  # ...<snip>
}

for further manipulating. To implement this a recursive read and update could be introduced:

code

{ lib, pkgs, ... }@args:
# https://gist.github.com/thalesmg/ae5dc3c5359aed78a33243add14a887d
let
  configPlace = "~/.config";

  inherit (builtins) readDir foldl' attrNames;
  inherit (lib.attrsets) filterAttrs setAttrByPath recursiveUpdate;
  inherit (lib) removeSuffix;
  inherit (pkgs) writeText;

  listRecursive = pathStr: listRecursive' { } pathStr;
  listRecursive' =
    acc: pathStr:
    let
      toPath = s: path + "/${s}";
      path = ./. + pathStr;
      contents = readDir path;
      dirs = filterAttrs (k: v: v == "directory") contents;
      files = filterAttrs (k: v: v == "regular" && k != "default.nix") contents;
      dirs' = foldl' (acc: d: recursiveUpdate acc (listRecursive (pathStr + "/" + d))) { } (
        attrNames dirs
      );
      files' = foldl' (
        acc: f:
        recursiveUpdate acc (
          setAttrByPath [ "${configPlace}${pathStr}/${(removeSuffix ".nix" f)}" ] (
            if lib.hasSuffix ".nix" f then
              (writeText (removeSuffix ".nix" f) (import (toPath f) args))
            else
              (toPath f)
          )

        )
      ) { } (attrNames files);
    in
    recursiveUpdate dirs' files';
in
listRecursive ""

This will structure the attribute set according to the directory structure. It also provides a mechanism for using variables, such as pkgs.hello, in the configuration. To do this, simply add the suffix .nix to the file name and wrap the file content with a Nix string.

e.g.

{pkgs, ...}:
''
foobar ${pkgs.hello}
''

will evaluated to:

foobar /nix/store/xxxxxxxxxxxxxxxxxxxxxx-hello

Make a new dir in whatever place of your config repo. Place default.nix in and you could copy target/*, which above mentioned, or your $HOME/.config if u don't use home-manager, into this directory. See structure or maybe a more elegant way.

This will read the entire dir and output a text:

mkdir -p /home/user/.config/alacritty; ln -sf ./alacritty/alacritty.toml /home/user/.config/alacritty/alacritty.toml
mkdir ...<snip>

Finally we need a nix app for deploying these.

{
# flake.nix toplevel
# may require edit, each-system config has automatically append by flake-parts in my case.
apps.default =
  let homeCfgAttr = (import ./home { inherit pkgs lib; });
      parent =
         let
           inherit (inputs.nixpkgs.lib)
             concatStringsSep
             reverseList
             splitString
             drop
             ;
         in
         p: concatStringsSep "/" (reverseList (drop 1 (reverseList (splitString "/" p))));
in
{
  type = "app";
  program = pkgs.writeScriptBin "link-home" (
    toString (
      lib.concatStringsSep "\n" (
        lib.foldlAttrs (
          acc: n: v:
          acc ++ lib.singleton "mkdir -p ${lib.parent n}; ln -sf ${v} ${n}"
        ) [ ] homeCfgAttr
      )
    )
  );
};

}

While config changed just run nix run and all will be set.

User-specific Packages

More easily. Add following to flake toplevel

{

  packages.default = pkgs.symlinkJoin {
    name = "user-pkgs";
    paths =
      import ./userPkgs.nix { inherit pkgs; }
      # avoid being gc
      ++ (lib.singleton (
        map (
          path:
          let
            source = homeCfgAttr.${path};
          in
          pkgs.writeTextDir path source
        ) (builtins.attrNames homeCfgAttr)
      ));
  };

}

and userPkgs.nix

{pkgs, ...}:
  with pkgs; [ hello cowsay ]

Trace by git.

while first deploy, run nix profile install .#userPkgs.

while changed, run nix profile upgrade <index> which index seen from nix profile list

NOTICE that if using root on tmpfs, ~/.nix-profile may not exsit at startup if home on tmpfs, which causes packages not loaded to env. Adding a link for solving this.

{
  systemd.tmpfiles.rules = [
    "L /home/${user}/.nix-profile - - - - /home/${user}/.local/state/nix/profiles/profile"
  ];
}

Final

You may need to pay attention to the behavior when garbage collection (GC) is executed, as discussed in the mentioned article.