nix.md

Nix

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What is Nix?

Nix is a cross-platform package manager that utilizes a purely functional deployment model where software is installed into unique directories generated through cryptographic hashes. It is also the name of the tool's programming language. A package's hash takes into account the dependencies, which is claimed to eliminate dependency hell.[2] This package management model advertises more reliable, reproducible, and portable packages.

https://en.wikipedia.org/wiki/Nix_(package_manager)

Installation

You will need a reasonably up to date nix install. I have attempted to make this script as backwards compatible as possible.

Install Nix - Recommended method

I recommend you use a distribution-spessific package for Nix. As it is currently more up to date than the official methods for installing Nix. Plus it ships with extra helpers to get nix running nicely under non-NixOS environments. This is especially true for SELinux-enabled distros like Fedora and CentOS.

Follow the steps: https://nix-community.github.io/nix-installers/.

In short, it would be to run the command below, swapping out with your package manager of choice:

$ sudo dnf install ~/Downloads/nix-multi-user-x.x.x.rpm

You can safely ignore any warnings about nixbld accounts. It is just informing you that nix is creating its nix-build accounts. These get removed when you run sudo dnf remove nix-multi-user.

Note on Fedora/CentOS

If you are running on Fedora/CentOS, i can also recommend making this file to let nixpkgs's version of OpenSSH to work without errors.

# /etc/ssh/ssh_config.d/10-nixpkgs-support.conf
Match all
    IgnoreUnknown "rsaminsize,gssapikexalgorithms"

Install Nix - Official method

If you cannot follow the method above, maybe due to running an exotic operating system that is not packaged above, you can follow the official instructions here: https://nixos.org/download.html.

Do be warned, this is a .sh script you run as root! It may mess up your system!

Once installed you will need to add this line into ~/.config/nix/nix.conf, or /etc/nix/nix.conf if you want it to be system-wide.

# ~/.config/nix/nix.conf
experimental-features = nix-command flakes

This will give you access to the modern nix commands (nix build/nix run), together with the nix flake subset of commands, which are for flake.nix and flake.lock files.

How Nix Functions

Nix downloads all its binaries to a location called /nix/store. So do not be afraid if you want to run packages you already have installed. Nix will not touch your normal system install.

For example, you can run htop from nixpkgs, the default repository for nix packages.

nix run nixpkgs#htop`

Now watch closely, as you can watch it download htop as well as any dependencies it will need.

TODO

nix develop

nix build

nix build -L

https://myme.no/posts/2022-01-16-nixos-the-ultimate-dev-environment.html#the-elevator-pitch

.#

Direnv

nix profile

nixpkgs search

Maintinence

TODO.

# Show all weakly-linked GC-roots (f.x. result folders that should be manually deleted).
ls -l /nix/var/nix/gcroots/auto/

# Remove all home-manager generations
home-manager expire-generations "-14 days"

# Remove all previous profile generations.
nix profile wipe-history

# Garbage collect all non GC-root derivations.
nix-collect-garbage

Or if you would like a quick "delete all" that will capture the worst offenders without having to worry too much:

# Unlink all previous generations and garbage collect (a handy all-in-one command).
nix-collect-garbage -d
# Clean up boot entries in systemd-boot/grub2.
/run/current-system/bin/switch-to-configuration boot

Recommended reading:

If you are new to Nix, i highly recommend you to spend an hour reading up on the topic. As it is wildly different from package managers that you are used to. If you want to avoid mistakes, and learn how to keep your Nix Store so that it won't start to eat up all the space on your computer? I can recommend reading about it now, and not learn about it later.

"Nix in my development workflow" is a great introduction for those who just want to get to up to speed with practically using nix.

Do keep in mind that we are using home-manager to manage packages, and not nix-env -i. Plus, upgrades are handled with flakes nix flake update instead of nix-channel --update.

https://medium.com/@ejpcmac/about-using-nix-in-my-development-workflow-12422a1f2f4c

Further reading

Then for those who are more interested in learning about Nix, i would recommend also looking at this meta resource with everything you should need to know: https://github.com/nix-community/awesome-nix.