Migrating to NixOS

QUICK DISCLAIMER:

I am by no means a NixOS expert, and I am still in the middle of migrating my hosts to NixOS.

I expect A LOT of time needed before this migration completes, but if you are curious: this is my repository for my NixOS configurations.

I am pretty sure there are a lot of room for improvement, and would love to see that pointed out if you have the time and will. Thanks in advance.

My Linux Journey #

I have long been an Arch and Fedora user.

For desktops and laptops, I went with Arch. I loved the capabilities Arch provides, without too much of a hassle - with GNOME or i3 most of the time. And for servers, I went with Fedora as that was the distro providing me new packages fast enough while being not easily prone to breaking if active maintenence is not in place.

There were still some exceptions. I used Gentoo for my LG laptop that is antic, I shall say - to the point where I’m still not sure what the actual model name is. I can pull stuff out to make that poor thing run packages even at the cost of loosing some functions.

But those were the two distributions I mainly used, before starting my migration to NixOS.

Why Though? #

I always loved the idea of using old tech as home servers from long ago, and am still running lots of them - one for Jellyfin, one for testing out stuff, one for a janky NAS - and the list goes on.

I won’t say they were not manageable. They were, kind of.

But managing heterogeneous systems accumulated over years introduced friction. Each machine, at some point in time, had its own:

• Package manager quirks and update cadences
• Init system differences - since Gentoo used OpenRC
• Undocumented dependencies I installed then forgot about

Reproducing a setup meant following notes that were never up to date, or cloning disks and hoping for the best. The “works on my machine” syndrome was real.

The breaking point came when one of my Fedora servers died for some reason. I had backups of data, but not the configuration — services, firewall rules, systemd timers, random packages installed to fix issues, etc. Rebuilding meant relearning all the stuff I had gone through already.

That was the moment I decided enough is enough.

Entering NixOS #

So after that painful rebuild, I finally made the decision to try out NixOS.

NixOS inverts the typical Linux administration model. Instead of running commands that mutate system state, you declare the desired state in a configuration file. The system then drives the steps to reach that state.

A NixOS configuration file, or a set of files, describes:

• Installed packages
• Enabled services and their configurations
• Users and permissions
• Firewall rules
• Kernel parameters
• Bootloader settings

… so, basically almost the whole system.

Rebuilding a machine just becomes one command:

Rollback is just a reboot away, configuration lives in version control, and the entire system state is reproducible.

While that sounds really attractive, that meant I had to go through and write those files to actually make use of them. That was the one restraint blocking me almost two years after hearing about NixOS and trying it out.

The Migration #

I’ll be honest here - the transition was not seamless.

Well, and I expected that to begin with. So this was my approach:

1. Start with new or non-critical machines
2. Desktop/laptop first, server later - I don’t want my servers breaking
3. Incrementally translated existing configs
4. Accepted that some conveniences - AUR - had Nix equivalents or required manual packaging
5. Embraced flakes and home-manager early
6. Separate files more than what seems optimal - even if that meant merging files later on

So the configuration, even to this date, is messy with a ton of files and mistakes here and there. But the payoff was pretty awesome. Adding new services means adding just one more file. Changes across all machines? One file edit.

Pains #

The Nix language itself was the first wall. It’s a whole purely functional language. Understanding how let...in, attribute sets, and function application work took time.

Then came module system subtleties: the difference between pkgs.writeShellScript vs pkgs.writeShellApplication, when to use config, options, and lib - it all accumulates fast.

{ config, pkgs, ... }: {
  services.nginx.enable = true;
  environment.systemPackages = with pkgs; [ vim git ];
}

The documentation, while improving, is still scattered across the NixOS manual, nixpkgs source, and community wikis.

In short: I’d say it was steep, but not at all unclimbable.

Where I am #

I have moved my primary laptop to NixOS, using the unstable branch. I love the updates coming quick and fast, and since this is my main machine I actively maintain it so I haven’t had an issue yet - and I hope that day never comes.

For servers, it’s a mixed bag. I still have most of them running Fedora or whatever is running right now. However I am in the middle of configuring a new system that will be used as a server with NixOS, and success for that machine means me starting the migration for my servers fully - so I am looking forward to that.

While Nix introduces a huge learning curve, I can really see its potential now and am happy committing to it. Writing configurations, while a HUGE time consuming job, is only happening once.

Oh, and for the old LG laptop? That’s still running Gentoo. It just didn’t have enough power to handle NixOS properly. I’ll probably have to let that machine go not faraway from right now, I guess.