How I use nix

In this article I'll explain how I use nix. I don't use NixOS nor any Linux as my main desktop environment¹. Still I use nix on a few mac computers. It has multiple usages.

First, let's start by the bad news. Recent macOS security policy made nix a bit harder to install on a mac. See macOS Installation instructions.

Once you have nix installed you should update the nix-channel. Mainly a nix-channels is where are the definitions of all the packages. See nixOS documentation.

Home Manager

First, I use home-manager, it's first usage it to list a reproductible list of application I need on all my desktop environments. So i edit the file ~/.config/nixpkgs/home.nix. I provide a list of packages I want to have when I start a new shell.

  home.packages = with pkgs; [
    # nix
    nix-prefetch-git
    lorri
    # emacs
    emacsMacport
    imagemagick
    gnupg
    # vim
    neovim
    # shell
    direnv
    fasd
    fd
    findutils
    fortune
    gawk
    git
    gitAndTools.diff-so-fancy
    graphviz
    htop
    httpie
    jq
    jwt-cli
    libressl
    mustache-go
    pandoc
    ripgrep
    rtv
    wakatime
    xpdf # pdftotext
    yadm
    youtube-dl
    # clojure
    leiningen
    boot
    adoptopenjdk-bin
    joker
    # Haskell
    ghc
    cabal-install
    (all-hies.selection
      { selector = p:
          { inherit (p) ghc865; };})
    # Common LISP
    sbcl
    # mails
    offlineimap
    notmuch
    msmtp
    gmailieer
    # docker
    docker-compose
    # weechat
    rel20weechat
    aspell
    aspellDicts.en
    aspellDicts.fr
  ];

There are a few noticiable artifact here:

The first one is rel20weechat is a very specify build of weechat with the plugin I need. So here is the block I use:

rel20 = import (fetchGit {
  name = "nixpkgs20";
  url = "https://github.com/NixOS/nixpkgs";
  # obtained via
  # git ls-remote https://github.com/NixOS/nixpkgs nixpkgs-20.03-darwin
  ref = "refs/heads/nixpkgs-20.03-darwin";
  rev = "58f884cd3d89f47672e649c6edfb2382d4afff6a";
}) {};
rel20weechat = rel20.weechat.override {
    configure = { availablePlugins, ... }: {
      # plugins = with availablePlugins; [ python perl guile ];
      scripts = with pkgs.weechatScripts; [ wee-slack ];
    };
  };

First rel20 pin a nixpkgs some specific commit of nix packages. Second, I overriden the default packages of the weechat package.

Another interresting one is this block:

let
  ...
  rel19 = import (fetchGit {
    name = "nixpkgs19";
    url = "https://github.com/NixOS/nixpkgs";
    ref = "refs/heads/nixpkgs-19.09-darwin";
    rev = "2f9bafaca90acd010cccd0e79e5f27aa7537957e";
  }) {};
  haskellDeps = ps: with ps; [
    base
    protolude
    tidal
    shake
    rel19.haskellPackages.sws
    ];
  ghc = pkgs.haskellPackages.ghcWithPackages haskellDeps;
  ...
in
  home.packages = with pkgs; [
    ...
    ghc
    ...
  ]

So it means I want to install ghc the main Haskell compiler. But also with some specific haskell packages. The interresting part, is that in most classical OS environment if you want a package from a specific language platform. You need to install the package manager for this language (npm, pip, etc…). And in nixpkgs there are formulae for most of these language specific packages. So instead of just installing cabal-install and then installing the packages I need. Which could also go bad, because they might be upgraded and not be compatible all at the same time.

I used nix to install the packages I needed. And one interresting detail. One package sws is broken in 20.03 on darwin. So I used the older version from 19.09.

¹: I'm using macOS, and I have multiple macs. A laptop and two desktop machines. Using the 27" iMac is my ultimate work station. It really enhance my productivity. Still the laptop is a superior work environment for more casual tasks. I guess I might write someday about my full work environment.

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How I use nix

Home Manager

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