nixos

content/post/home-manager.md

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+---
+title: "NixOS and Home Manager"
+description: 
+date: 2025-08-31T18:53:25+02:00
+image: /img/nixos.svg
+math: 
+license: 
+hidden: false
+comments: true
+draft: false
+---
+
+Nix is a declarative package manager (and its main language) that allows for reproducible environments (i.e., files in a folder).
+
+One of the cool things about nix is that you can use it to run a package without installing it permanently in your system.
+For instance, I recently needed the `readelf` utility and it wasn't installed in my system, so I ran:
+
+```
+nix run 'nixpkgs#toybox' -- readelf -l /home/j/.local/share/uv/python/cpython-3.10.11-linux-x86_64-gnu/bin/python | grep interpreter
+```
+
+That's it.
+No need to deal with dependencies, incompatibilities, or to uninstall the package once you no longer need it.
+
+NixOS is a Linux Operating system that uses this package manager and system configuration (e.g., users, network interfaces, etc.) defined in the Nix language to create reproducible systems.
+
+Home-manager takes the concepts from NixOS to user-space, allowing you to define your personal environment (i.e., home).
+It can be used on any system that supports the Nix package manager (e.g., Linux, Mac and Windows).
+
+There is a lot to like 
+
+## Context
+
+(Last year)[https://github.com/balkian/dotfiles/commit/fa7041ff8bde6c5288ad55db6b0d61ed593bbccc] I started experimenting with nix and home-manager to configure my environments.
+The context is that for some years now I've been switching devices quite frequently.
+It started when my main laptop died (DELL!!), I started using a desktop for most of my work, but I also needed a laptop to teach.
+One thing led to another, and I ended up using vanilla Ubuntu or EndeavourOS installations with Gnome and very minimal customization.
+That in itself is not wrong.
+The thing is that, before that, I was a [tinkerer with a customized environment](https://github.com/balkian/dotfiles).
+
+
+1. I was being inefficient (and I felt it)
+2. That inefficiency turned some easy things into a chore
+3. This made work in general less enjoyable.
+3. As a result, I became even less productive
+
+The idea was to get back to a usable terminal and editor setup with minimal
+
+
+## NixOS
+
+I've only been running NixOS for three days now, but so far I like the experience.
+My approach is to keep the system definition as simple as possible, and rely on home-manager to install and configure most of my tools.
+The basics would be:
+
+* Network configuration
+* System users
+* Desktop environment (wayland and multiple DE's)
+
+All that goins into my `/etc/nixos/configuration.nix`, and then I do:
+
+```
+sudo nixos-rebuild switch
+```
+
+If it fails, nothing is changed in your system.
+If it works, most of the changes will have been applied (e.g., new services started, others stopped).
+The previous configuration does not disappear: you can roll back to it manually or when booting your system.
+
+## Home-Manager
+
+Here's where most of my configuration lives.
+I use `homeConfigurations` to keep more than one configuration in the same repo (e.g., work (`j@lenny`) and personal computers (`j`, on any other system)).
+
+To make it easier to install this configuration
+
+### Running on NixOS
+
+There are two ways to run it: as part of your general configuration (i.e., it will be applied using the same `nixos-rebuild` command) or standalone.
+I prefer the latter, because it allows me to tinker with the configuration more easily, and it is no different from applying it on other systems (see below).
+After you change your config, simply run:
+
+```
+home-manager switch
+```
+
+### On other systems
+
+Running nix on other operating systems (e.g., Arch Linux) is similar to a standalone installation on NixOS.
+The only difference is that you need to [install nix first](https://nix.dev/install-nix.html) and [configure the appropriate channels](https://nix-community.github.io/home-manager/index.xhtml#sec-install-standalone).
+
+
+## It's a little flakey
+
+Flakes are an experimental feature of nix that use version control and some special conventions to bring more reproducibility guarantees.
+For instance, they make it trivial to install a specific commit version of my home-manager config, which in itself could use program definitions from external git repositories.
+Flakes are not the only solution to this problem, and they are a bit controversial among hardcore nix users.
+However, the community as a whole seems to have embraced flakes.
+
+I personally chose to set up my config as a flake.
+I still have not tried to install it on other systems, so time will tell.