My User Environment

Overview

This repository represents the state of the environment(s) I’m currently using for development, learning and, to some degree, entertainment. Currently there are only NixOS machines (plus one WSL2 environment that I need to include at some point) I manage this way:

• atuan: my home PC
• tehanu: my new work laptop
• angband: a tiny notebook (64 GB of disk space only) I use when traveling
• paln: a tiny Hetzner Cloud VM I use for synchronization and small backups

  The actual (development) environments are managed with home-manager. home-manager makes it possible and easy to bundle binaries / packages with their respective configuration (usually files inside the home directory or $XDG_CONFIG_HOME).

  In the past I was using macOS as well as Ubuntu, but have since fully transitioned. Note that using a nearly identical setup powered by the Nix package manager and home-manager is not that different. Only a handful of things are actually managed by the underlying system anymore. (If you’re interested, you should look up how to create a homeConfigurations.<username> output in your flake.nix, replacing the nixosConfigurations.<hostname> one.)

Repository and flake structure

NixOS systems

The nixos directory contains the machine/host-specific pieces of configuration. Every subdirectory will lead to a flake output under nixosConfigurations, with the attribute name being the name of the directory.

The directories itself follow a fixed convention:

• configuration.nix and hardware-configuration.nix (automatically created when installing NixOS on the machine for the first time) together constitute the NixOS configuration
• home.nix is the home manager configuration
• custom.nix contains everything that should be passed to all the NixOS and home manager modules as arguments; usually this (only) means things that should be known everywhere, like my username

The modules directory contains the home manager NixOS modules that all my configurations share (but might choose to disable or enable on a per-machine basis).

Home-manager on non-NixOS

The users directory contains home-manager-only configurations for my non-NixOS machines. At the moment my work laptop runs both NixOS and Void Linux, and on the latter I use home-manager first-class.

Install a new generation with

home-manager switch --flake ~/dotfiles --impure

(The --impure argument is due to the fact that on non-NixOS systems, applications using OpenGL (or similar) often fail on startup; nixGL helps with this problem, but installing it requires this parameter).

Building/switching to a new generation

I usually use an alias in my shell to switch to the next generation after changing things in my configuration. The actual command is the following:

nixos-rebuild switch --use-remote-sudo --flake ~/dotfiles

The --flake ~/dotfiles part works because of two reasons:

• I always clone this repository into my $HOME.
• The command performs a lookup on the hostname of the machine; if the flake.nix contains an output nixosConfigurations.<hostname>, this is the configuration that will be used.

It’s also possible to only switch into the next home-manager generation for the current user without adding a new system generation using the following command (which is yet another shell alias):

nix shell "~/dotfiles/#nixosConfigurations.$(hostname).config.home-manager.users.$USER.home.activationPackage" \
          --command home-manager-generation

Note, however, that without creating a new system generation these changes will not be “activated” upon next boot.

Emacs configuration

A special case of a program with a relatively huge accompanying configuration is GNU Emacs. My literate Emacs configuration (very much a work-in-progress, as I’ve only recently started going back to using Org Mode to configure Emacs itself) can be found here.

Note that there is a corresponding default.nix which specifies the version of Emacs I use (usually a quite recent one, made possible by emacs-overlay), as well as some pre-built packages, all “obeying” my current pin of nixpkgs (see flake.lock). I used to use Nix to manage all of my Emacs packages, but have since switched to straight.el, as it allows me to more quickly change my config, try out new packages on the fly without cluttering anything, and even debug packages.