I had been using Arch Linux for a while and, while I was comfortable with it, I felt the urge for a change. Arch served me well, but I wanted to give NixOS a try again - without losing any data. Thankfully, I retained my home partition, so I could make the transition to NixOS without any risk of losing my files. Everything stayed intact.

Speaking of personal configurations, I've set up my Emacs environment to be just how I like it. Emacs is the cornerstone of my development setup, so getting it configured perfectly is essential. NixOS makes it easy to package and manage Emacs along with all its extensions and customizations.

I'm not going to show my Emacs config just yet, that's for another day. But I will tell you how to use my custom Emacs build.

{pkgs,...}: 
let
  modifiedEmacs = pkgs.emacs30-pgtk.overrideAttrs (oldAttrs: {
    configureFlags = oldAttrs.configureFlags ++ [
      "--with-gnutls"
      "--without-xwidgets"
      "--with-tree-sitter"
      "--with-png"
      "-with-jpeg"
      "--without-wide-int"
      "-with-sound"
      # "--without-native-compilation"
      # "--with-pgtk" # means lucid won't work
      # "-with-x-toolkit=lucid"
      "--with-libsystemd"
      "-with-dbus"
      "--with-pdumper=yes"
      "--without-pop"
      "-without-mailutils"
    ];
  });
in
modifiedEmacs

This package override will thus smartly rebuild the Emacs package from source whenever the NixOS package gets an update. Is this somewhat like what Portage does on Gentoo? Guess I'll know when I try it out!

I've also added mu4e somewhere in my configuration - I need a decent email client too ;).

• One thing I recommend is modularizing your configuration as early as possible.

It's (obviously) convenient to keep the config in a single file (2 if you consider the autogenerated hardware-configuration.nix file), but this works well only for small configurations. I've had difficulties managing my configuration even when it was split across 7-8 files (yes, skill issue 🤧).

But now I've managed to get a hold of things because I've split the config like this:

Note that the root directory here (i.e ~/.nixos), contains my flake.nix file that automatically imports the appropriate configuration.nix files according to the hosts defined.

I don't have multiple devices for now, so Krypton is the only host in active use (apart from the generic VM config of course). But this setup makes it trivial to add new hosts because common configuration goes into the common/ folder.

NixOS has a steep learning curve, but by breaking your configuration into manageable pieces, you can stay organized and avoid overwhelming yourself.

Each module can be a small, self-contained piece that focuses on a specific task (e.g., configuring the system, managing the package manager, setting up user configurations, etc.).

It's a bit of upfront effort, but it'll save you a lot of headaches down the road.

Of course, NixOS isn't without its challenges. One of the biggest pain points I faced was the issue with arbitrary binaries. I had a lot of trouble running certain binaries last time I tried NixOS, and it was frustrating. However, things have improved. Tools like nix-ld and distrobox have become much more reliable. The NixOS ecosystem has also grown significantly—repositories have expanded from around 80k packages to over 120k as of now. A lot of software is now available, and the number of flakes (the pre-configured, reusable configurations I've mentioned above) has increased as well.

That said, some software may still not be packaged, but that's not a huge deal. When that happens, I just use distrobox to run a containerized version of the software, which has been a solid workaround.

Another important pitfall is that the Nix language isn't very straightforward. The documentation is severely lacking - but this issue permeates across a good part of the Nix ecosystem anyways. For those not used to functional programming, the language might seem like an uglier JSON.

In the end, returning to NixOS has been an exciting experience. It's not perfect, but it's certainly a great option for those who enjoy fine-tuning their system. I'm happy with my decision, and I look forward to exploring NixOS even further.