presentation-nix-flakes/prezentace.md

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true	invert	true	Albert Vala, Filip Kohout, Nix flakes & Nix command

Nix flakes & Nix command

---

Nix Command

• Nové nix cli
• Flake support

---

Porovnání

nix-shell -p cowsay #Old
nix shell nixpkgs#cowsay #New
nix run nixpkgs#cowsay #New

---

Commandy

Command	Na
flake new	Vytvoření flaky z template
develop	Build environment shell
shell	temp shell s nějakým programem
config check	Check configu na potenciální chyby
run	Spustí output z flaky

---

Flakes

• Proč?

• Lockfiles.

• Flake inputs

• Na co?

• Cokoliv.

---

Nix command + flakes

• temp shell

nix shell nixpkgs#alejandra
nix shell github:kamadorueda/alejandra

• Show output attr

nix flake show github:kamadorueda/alejandra

---

Jak použít flakes na systémovou configuraci?

• Flakes používáme jen na management input a output atributů
• Zbytek konfigurace používá inputy definované ve flake.nix

---

# flake.nix
{
  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
    home-manager.url = "github:nix-community/home-manager";
    home-manager.inputs.nixpkgs.follows = "nixpkgs";
    zen-browser.url = "github:0xc000022070/zen-browser-flake";
  };
  outputs = inputs @ {
    nixpkgs,
    home-manager,
    zen-browser,
    ...
  }: {
    nixosConfigurations = {
      nixos = nixpkgs.lib.nixosSystem {
        system = "x86_64-linux";
        modules = [
          ./configuration.nix
          home-manager.nixosModules.home-manager
          {
            home-manager.useGlobalPkgs = false;
            home-manager.useUserPackages = true;
            home-manager.extraSpecialArgs = {inherit zen-browser;};
            home-manager.users.nixFreak = import ./home.nix;
          }
        ];
      };
    };
  };
}

---

# home.nix
{
  zen-browser,
  config,
  pkgs,
  ...
}: {
  home.username = "nixFreak";
  home.homeDirectory = "/home/nixFreak";
  home.stateVersion = "24.05";
  home.packages = with pkgs;
    [
      cowsay
    ]
    ++ [
      zen-browser.packages."${system}".default
    ];
  programs.home-manager.enable = true;
}

---

# configuration.nix
{
  config,
  lib,
  pkgs,
  ...
}: {
  imports = [
    # Include the results of the hardware scan.
    ./hardware-configuration.nix
  ];

  boot.loader.systemd-boot.enable = true;
  boot.loader.efi.canTouchEfiVariables = true;
  users.users.nixFreak = {
    isNormalUser = true;
    extraGroups = ["wheel"];
  };
  system.stateVersion = "25.05";
}

---

Nová flake z full templatu

• nix flake init --template templates#full

---

Inputs

• nix flake metadata --json | jq - zobrazí vstupy
• lock aktuální verze
• nix flake update - aktualizace všech vstupů
• nix flake update [home-manager] - aktualizace jednoho vstupu

 inputs = {
    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
    nixpkgs-stable.url = "github:nixos/nixpkgs/nixos-24.11";
    nixpkgs-current = "github:nixos/nixpkgs?ref=3058cf84bce1aba7b1820cb24319a171572217ba-dirty";
 }

---

Nixos-rebuild

• Je to jen bash script

nixos-rebuild --flake
nh os switch

nix build /etc/nixos#nixosConfigurations.nixos.config.system.build.toplevel
./result/bin/switch-to-configuration switch

---

Remote building

• nixos-rebuild --target-host nixFreak@192.168.8.32 switch --flake .#default

• --use-remote-sudo

• --build-host - konfigurace tady

• --target-host - konfigurace tam

• nix.settings.trusted-users

---

Virtual machine

• nix run github:nix-community/nixos-generators -- -c ./flake.nix --flake '#default' -f vm --disk-size 20480
• nixos-rebuild build-vm --flake ~/my-system-flake#default
• možnost generovat pro různé platformy (Amazon E2C, Docker, ISO, Proxmox, VMware, vagrant, qcow, ...)
• https://github.com/nix-community/nixos-generators

---

Nix Shell

• nix-shell ./

# shell.nix
{pkgs ? import <nixpkgs> {}}:
pkgs.mkShell {
  packages = [
    (pkgs.python311.withPackages(pypkgs: with pypkgs; [
      requests
      numpy
      pygobject3
    ]))
  ]
}

---

#flake.nix
{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    flake-utils.url = "github:numtide/flake-utils";
  };
  outputs = {
    self,
    nixpkgs,
    flake-utils,
  }:
    flake-utils.lib.eachDefaultSystem
    (
      system: let
        pkgs = import nixpkgs {
          inherit system;
        };
      in
        with pkgs; {
          devShells.default = mkShell {
            packages = [
              (pkgs.python311.withPackages (pypkgs:
                with pypkgs; [
                  requests
                  numpy
                  pygobject3
                ]))
            ];
          };
        }
    );
}

---

Nix language

• nix-repl nebo nix-instantiate --eval foo.nix

# Deklarace setu
 foo = {
  bar = "test"
 }

# "Čtení" setu (evaluation)
foo.bar

# Let-In syntaxe
let 
  foo = {
    bar = "test"
  };
in
foo.bar

---

# Rekurze
 foo = rec {
  bar = 10;
  ham  = 5;
  eggs =  bar + ham;
 }

# Použití with
 environment.systemPackages = with pkgs; [
  neovim
  wireshark
 ];

---

Funkce

# Jednoduchá funkce
let 
 bar = eggs: eggs + 1;
in
 bar 3 # -> 4

# Funkce s více parametry
let 
 bar = eggs: bacon: (eggs+1) * bacon;
in
bar 3 7 # -> 28

---

let 
 bar = { bacon, eggs }: bacon + eggs;
in
 bar { bacon = 10; eggs = 15; }

• konfigurační soubory jsou funkce

# configuration.nix
{inputs, pkgs}:
{
  environment.systemPackages = [
    inputs.zen-browser.packages.${system}.default
    pkgs.gcc
  ];
}

---

let 
 bar = { bacon ? 10, eggs, ... }: bacon + eggs;
in
 bar { eggs = 15; bread = 30 }

let 
 bar = { bacon ? 10, ... }@arguments: 
  bacon + arguments.eggs;
in
 bar { eggs = 15; bread = 30; }

---

 outputs = inputs @ {
    nixpkgs,
    home-manager,
    zen-browser,
    ...
  }: {
    nixosConfigurations = {
      nixos = nixpkgs.lib.nixosSystem {
...

---

Nix writers

• Jednoduchý způsob přidávání skriptů v různých programovacích jazycích do systému
• Rozdíl oproti klasickému pkgs.writeShellScriptBin
• nixpkgs - pro všechny možnosti konfigurace skriptů
• https://nixos.wiki/wiki/Nix-writers - wiki

---

pkgs.writers.writeBash "hello-world-bash" {}
''
echo "Hello world!"
''

pkgs.writers.writePython3 "hello-world-python" {}
''
print("Hello world!")
''

pkgs.writers.writeRust "hello-world-rust" {}
''
fn main() {
    println!("Hello world!")
}
''

---

pkgs.writers.writePython3 "hello-world-python"
{
    libraries = [ pkgs.python3Packages.requests ];

    makeWrapperArgs = [
        "--prefix", "PATH", ":", "${pkgs.sl}/bin",
    ];
}

''
print("Hello world!")
''

---

Děkujeme za pozornost.