June 2, 2022

Another nix post in the wall

Starting

Are you using Nixos? This is not for you. Do you want multi-user installation? This is not for you. This is only useful if you want to use both flakes and home-manager.

Single-user installation (no sudo needed, easier to remove, good for testing purposes)
```
  sh <(curl -L https://nixos.org/nix/install) --no-daemon
```
Source the new profile or login. . ~/.nix-profile/etc/profile.d/nix.sh
Since most of the nix “guides” are outdated, check what your current version supports nix --help, ~~at the time of writing this, there’s no need to enable experimental features for flakes :)~~ spoke too soon.

Upgrading nix:

  nix-channel --update; nix-env -iA nixpkgs.nix nixpkgs.cacert

Check if nixpkgs-unstable channel (package sources basically) is installed or not by nix-channel --list
You can look at user-installed packages by nix-env --query

Home manager

Allows declarative configuration of user-specific (non global) packages and dotfiles.

Installation

nix-channel --add https://github.com/nix-community/home-manager/archive/master.tar.gz home-manager
nix-channel --update

In .bash_profile. (might not be needed for single-user systems, check back later)

export NIX_PATH=${NIX_PATH:+:$NIX_PATH}$HOME/.nix-defexpr/channels:/nix/var/nix/profiles/per-user/root/channels

In your .bash_profile, add below and source the profile for your current session.

source "$HOME/.nix-profile/etc/profile.d/hm-session-vars.sh"

Configuration

Now check ~/.config/nixpkgs/home.nix, if it exists then for the most part you’ve successfully installed (not sure about configuration) home-manager. Building a configuration produces a directory in the Nix store that contains all files and programs that should be available in your home directory and Nix user profile, respectively. Run home-manager build to successfully verify. Also periodically check home-manager news for updates regarding new changes to packages that are referred in your config. After adding some packages (section 2.1), run home-manger switch.

Fleyks (sorry)

Flakes allow us to define inputs (you can think of them as dependencies) and outputs of packages in a declarative way and allow for dependency pinning using locks. As of writing this (June 2022) flakes are still experimental, so they must be enabled explicitly.

nix-env -iA nixpkgs.nixFlakes

This replaces nix 2.9.0 with 2.8.1? Look into why that’s happening. For now we enable experimental features.

mkdir -p ~/.config/nix
echo 'experimental-features = nix-command flakes' >> ~/.config/nix/nix.conf

The documentation is so stinky for flakes, like there are n variants sayings \(n^2\) different things, so for now I’m just winging it. Comment out the stateVersion from home.nix and in the same directory create a flake.nix. Replace jdoe with your username. Also the stateVersion can be changed accordingly to upgrade your home-manager.

{
  description = "Home Manager configuration of Jane Doe";

  inputs = {
    # Specify the source of Home Manager and Nixpkgs
    home-manager.url = "github:nix-community/home-manager";
    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
    home-manager.inputs.nixpkgs.follows = "nixpkgs";
  };

  outputs = { home-manager, ... }:
    let
      system = "x86_64-linux";
      username = "jdoe";
    in {
      homeConfigurations.${username} = home-manager.lib.homeManagerConfiguration {
        # Specify the path to your home configuration here
        configuration = import ./home.nix;

        inherit system username;
        homeDirectory = "/home/${username}";
        # Update the state version as needed.
        # See the changelog here:
        # https://nix-community.github.io/home-manager/release-notes.html#sec-release-21.05
        stateVersion = "22.05"; # TODO add current unstable home-manager version

        # Optionally use extraSpecialArgs
        # to pass through arguments to home.nix
      };
    };
}

Now it’s time to flake-ify your hm. Here <flake-uri> would be path:.config/nixpkgs assuming your pwd is ~.

  home-manager switch --flake '<flake-uri>#jdoe'

The flake inputs are not upgraded automatically when switching. The analogy to the command home-manager --update … is nix flake update. If updating more than one input is undesirable, the command nix flake lock --update-input <input-name> can be used.

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