Nix and NixOS

(the future of Linux Distributions)

Carsten Strotmann

Created: 2020-10-16 Fri 14:47

About me

living in north-west Germany (Münsterland)
Interests
- operating systems (Linux, xBSD, MacOS, Plan 9, SerenityOS …)
- retro computing (6502, 8086, m68k, Z80 …)
- DNS/DNSSEC/DANE/DoT/DoH, IPv6, DHCP
- lean Internet (Gopher, Gemini, FujiNet …)
- Programming (Go, Forth, Lua, Python, Oberon, Lisp …)
- Emacs
- Pen & Paper RPG

Software installation on Linux Distributions

classic Linux distributions

Debian, Ubuntu, Suse, Fedora, Red Hat, Arch-Linux, Void …
Iterative software installation and configuration
1. OS installation
2. initial software installation via packet manager (yum, dnf, zypper, apt, pacman …)
3. initial configuration
4. more software installation
5. more configuration
6. loop to –> 4

Iterative approach

the system grows over time
hard to replicate
generates unique machine configurations

The search for solutions

configuration orchestration
- TerraForm
- Ansible
- SaltStack
- others …
these solutions are external to the Linux distribution ecosystem
- the Linux distribution package manager does not know about Ansible and friends

About Nix

Nix

Nix is a packet manager
- multi platform (Linux, MacOS, FreeBSD)
- can be used in addition to the platform packaging infrastructure
- MIT License
Nix is a programming language
- pure, lazy, functional
- not a full-featured, general purpose language
- its main job is to describe packages, compositions of packages, and the variability within packages

https://nixos.org/features.html

Nix is functional

Nix is a purely functional package manager
it treats packages like values in purely functional programming languages such as Haskell
- they are built by functions that don’t have side-effects
- they never change after they have been built
- reproduceable packages

About NixOS

NixOS

NixOS is a GNU/Linux distribution
- build around the Nix package manager
- declarative system configuration
- reliable upgrades
- atomic upgrades
- rollbacks
- reproducible system configurations
- source-based, with binaries

https://nixos.org

NixOS - features

X11/Wayland/Plasma/Gnome/i3/sway/…
systemd
all the popular software (emacs, vim, apache, nginx, postfix …)
40.000+ packages
automatic hardware detection

About Home-Manager

Home-Manager: Nix for home directories

a basic system for managing a user environment using the Nix package manager
uses the Nix libraries found in Nixpkgs
allows per user installation of packages without root permissions

https://nixos.wiki/wiki/Home_Manager

About Guix/GuixSD

Guix/GuixSD

The GNU Guix package and system manager is a free software project by the GNU Project
- its the GNU flavored fork of the Nix idea
uses Scheme as the underlying configuration and declaration language
GuixSD is the Guix System distribution - a GNU/Linux Linux distribution around Guix
- GPLv3+ License

Starting with Nix

Installing Nix

as a normal user with sudo privileges

$ sh <(curl -L https://nixos.org/nix/install)

verify that the installation was successful

$ nix-shell -p nix-info --run "nix-info -m"

Installing from source

Nix can be installed from source

$ git clone https://github.com/NixOS/nix
$ cd nix
$ ./bootstrap.sh
$ ./configure [options...]
$ make
$ sudo make install

Install Home-Manager (using Nix)

my recommendation: install home-manager first and then manage all packages from there (declarative style)

nix-env -i home-manager

Exploring the Nix store

all Nix related files are stored unter /nix
Nix binaries and config files are symlinked into the user environment (search path)
a Nix-System file system layout qcan look weird to old skool linux hackers

[root@nixos:~]# ls -l /usr
total 0
drwxr-xr-x 2 root root 17 Sep 11 20:54 bin

Nix/Home-Manager Workflow

Finding packages

Search NixOS packages

nix search emacs

Install packages globally (NixOS)

add package to /etc/nixos/configuration.nix

environment.systemPackages = with pkgs; [                                                                                                                                   
  parted                                                                                                                                                                   
  emacs                                                                                                                                                                    
  gcc                                                                                                                                                                      
  gawk                                                                                                                                                                     
  [...]
  home-manager                                                                                                                                                             
];

next run nixos-rebuild switch

Install packages for a user (Home-Manager)

add package to the users ~/.config/nixpkgs/home.nix

{ config, pkgs, ... }:
{
  home.packages = with pkgs; [
      gtop
      unzip
      mc
      [...]
    ];
  };
}

then run home-manager switch as the user

Views on packages

Nix/NixOS provides different views on the installed packages
- all packages are located below the Nix store /nix/store/...
- users have different packages linked into their environment

Declarative Configuration (OS)

configuration for the Linux system and for applications can be done in declarative style
Nix creates the configuration files

{
  boot.loader.grub.device = "/dev/sda";

  fileSystems."/".device = "/dev/sda1";

  services.sshd.enable = true;
}

Declarative Configuration (User Programs)

declarative configuration works the same for user directories with the help of home-manager

services.gpg-agent = {
  enable = true;
  defaultCacheTtl = 1800;
  enableSshSupport = true;
};

Updating the system (NixOS)

update the channel information
```
# nix-channel --update
```
rebuild the OS with updated packages
```
nixos-rebuild switch --upgrade
```

Booting into different generations of the OS

NixOS allows to select the generation of the local NixOS build at boot time
- on regression, the user can boot an older version of the OS
to make room, older versions can be grabage collected
- manually with nix-collect-garbage
- automatically on a trigger (storage free space threshold)

Nix Shell / Development environments

the command nix-shell creates an ad-hoc environment
- including the listed packages and derivations
- the packages and environment is gone when the shell exits
- great for development environments

$ fossil
-bash: fossil: command not found
$ nix-shell -p fossil
[nix-shell] $ fossil
Usage: fossil COMMAND ...
   or: fossil help           -- for a list of common commands
   or: fossil help COMMAND   -- for help with the named command

Commands and filenames may be passed on to fossil from a file
by using:

    fossil --args FILENAME ...

Learning Nix

Next - NixCon

Talks. Discussions. Hacking
16. - 17. October - ONLINE
https://2020.nixcon.org

Questions? Discussion!

@cstrotm@mastodon.social

https://blog.defaultroutes.de (German)

Hands-On Nix

Instructions: https://blog.defaultroutes.de/nixos/