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# Nix flakes & Nix command

---

# Nix Command

* Nové nix cli
* Flake support

---

# Porovnani

```shell
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
```shell
nix shell nixpkgs#alejandra
nix shell github:kamadorueda/alejandra
```
- Show output attr
```shell
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

---

```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;
          }
        ];
      };
    };
  };
}
```

---

```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;
}
```
---
```nix
#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"]; # Enable ‘sudo’ for the user.
  };
  system.stateVersion = "25.05"; # Did you read the comment?
}
```

---

# 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

```nix
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

```shell
nixos-rebuild --flake
nh os switch
```

```shell
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

---

# Virtual machine

* `nix run github:nix-community/nixos-generators -- -c ./flake.nix --flake '#default' -f vm --disk-size 20480`

---

# Nix writers

* Jednoduchý způsob přidávání skriptů v různých programovacích jazycích do
  systému ve flake konfiguraci
* Rozdíl oproti klasickému `pkgs.writeShellScriptBin`
* [nixpkgs](https://github.com/NixOS/nixpkgs/blob/master/pkgs/build-support/writers/scripts.nix) -
  pro všechny možnosti konfigurace skriptů
* [https://nixos.wiki/wiki/Nix-writers](https://nixos.wiki/wiki/Nix-writers) -
  osekaná wiki

---

```nix
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!")
}
''
```

---

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

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

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