title: Nix: the Functional Package Manager
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layout: true

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# {{title}}

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### <https://doomhammer.info/talks/lambdadays2020>

# Piotr Gaczkowski

![DoomHammer](img/doomhammer.jpg)

<https://github.com/DoomHammer> | <svg aria-hidden="true" focusable="false"
data-prefix="fab" data-icon="twitter" class="svg-inline--fa fa-twitter fa-w-16"
role="img" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512" height="1em"><path fill="currentColor" d="M459.37 151.716c.325 4.548.325 9.097.325 13.645 0 138.72-105.583 298.558-298.558 298.558-59.452 0-114.68-17.219-161.137-47.106 8.447.974 16.568 1.299 25.34 1.299 49.055 0 94.213-16.568 130.274-44.832-46.132-.975-84.792-31.188-98.112-72.772 6.498.974 12.995 1.624 19.818 1.624 9.421 0 18.843-1.3 27.614-3.573-48.081-9.747-84.143-51.98-84.143-102.985v-1.299c13.969 7.797 30.214 12.67 47.431 13.319-28.264-18.843-46.781-51.005-46.781-87.391 0-19.492 5.197-37.36 14.294-52.954 51.655 63.675 129.3 105.258 216.365 109.807-1.624-7.797-2.599-15.918-2.599-24.04 0-57.828 46.782-104.934 104.934-104.934 30.213 0 57.502 12.67 76.67 33.137 23.715-4.548 46.456-13.32 66.599-25.34-7.798 24.366-24.366 44.833-46.132 57.827 21.117-2.273 41.584-8.122 60.426-16.243-14.292 20.791-32.161 39.308-52.628 54.253z"></path></svg> [@doomhammerng](https://twitter.com/doomhammerng)

<https://doomhammer.info>

---

# Package Management is Hard

Which package manager do you use?

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- Apt-get, RPM, ...

- Homebrew

- pip, gem, npm, cabal, ...

- Docker

- Helm?
]

---

---

Nix is a domain-specific, purely functional, lazily-evaluated language

Nix-lang – the language

Nix – the software

Nixpkgs – the Package Repository

NixOS – the Operating System

---

- Operates in userland

- Deterministic packages and environments

- Atomic upgrades

- Rollbacks

- Build environment management

- Multiple versions of packages side-by-side on a single system

- Runs on Linux and macOS

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- Installing or upgrading package won't break other packages

- Every package is installed in a separate directory

- It allows easy rollback

- Prevents inconsistent state

---

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- Several users can install packages without superuser privileges

- Different users can have different package versions

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# Package Manager

---

---

- Nix expressions are deterministic

- ... as far as network connectivity goes

---

`nix-env --list-generations`

`nix-env --rollback`

`nix-env --switch-generation 3`

`nix-env -G 3`

---

Closures are packages with their dependencies.

Closure can be copied between systems.

They can be exported to files and imported later on.

Or they can be copied over SSH.

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background-image: url(img/javardh-0z7r3FIyXcE-unsplash.jpg)

Creates a Nix environment based on a Nix derivation and enters a shell inside
it.

Good for portable development environments.
]

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background-image: url(img/brett-jordan-MFLNpz5FZRk-unsplash.jpg)

A list of all the software we have hoarded so far.
]

---

Uses `nix-shell`.

Automatically sets up development environment whenever you enter a directory.

You can pin the packages version.

---

.envrc

```bash
use_nix
. env/bin/activate
```

default.nix

```nix
{ pkgs ? import <nixpkgs> {} }:

with pkgs;

let
  python = python37;
in
mkShell {
  buildInputs = [ python git gnumake ];
}
```

---

lorri is a nix-shell replacement for project development. lorri is based around fast direnv integration for robust CLI and editor integration.

---

# Using Nix in Standalone Scripts

```elixir
#! /usr/bin/env nix-shell
#! nix-shell -p "elixir"
#! nix-shell -i elixir
current_process = self()

# Spawn an Elixir process (not an operating system one!)
spawn_link(fn ->
  send(current_process, {:msg, "hello world"})
end)

# Block until the message is received
receive do
  {:msg, contents} -> IO.puts(contents)
end
```

---

- Still not as easy as Homebrew

- GNU Guix using GNU Scheme (LISP)

- ... if you love parentheses, you'll love GUIX!

- ... also works with direnv!

---

# Inspiration

Asko Soukka @ PyCon PL 2019

<https://www.youtube.com/watch?v=Vnq6ngcqJAg>

---

# Thank you!

![DoomHammer](img/doomhammer.jpg)

<https://doomhammer.info>

### <https://doomhammer.info/talks/lambdadays2020>