Custom Options and If-else Statements in Your NixOS Config

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Hello everyone! Merry Christmas! I haven't posted in a while.. I'm back again today with another NixOS video (which I admittedly made a long time ago, but just haven't had a chance to post).

This discussion is about custom options and if-else statements for your NixOS configuration. Thanks for watching! Please subscribe for more NixOS/Linux/FOSS content!

Links referenced:

My configuration (if you're curious):

[MarcLacoursiere]

This video just saved me hours of tinkering... especially the part that explains why a config set must be created when some option declaration exist.

[vaisakh_km]

Best Series on nix ever Period

😭 For fist time in my life, i actually understood nix and declarative....

i have been using nix for 6-8 months having no idea what's going on, today i understood

[NicolasBPierron]

Just a few notes:
- Options are declared in the `options` attribute set, and defined in the `config` attribute set.
- Presenting `if .. then .. else ..` in the context of modules is a recipe for infinite loop as soon as you want to wrap more than a single option definition, which is why `mkIf` got introduced.

Apart from that, this is a nice walk-through on how to add variability to existing`configuration.nix` / `home.nix` modules, which starts to make sense as soon as you want to reuse code with some minor differences.

[RobFisherUK]

Excellent. What I really like about your explanations is that they include *what's really happening*.

So the config/options things and how omitting both is really a shortcut makes everything make sense.

And even the little things, such as : "attribute set containing an attribute set" where others say slightly inaccurate things like "nesting curly braces is a shorthand for the dots".

Btw: how different data types merge would be an interesting thing to go over at some point.

[pldcanfly]

Thank you for your videos. How you explain NixOS really makes it click for me and helps to organize the initial confusion about what the configs job is, what a flake does differently (and especially that it's not a 1:1 replacement for the configuration.nix-file, but rather another way to read it) and where home-manager comes in, and what it does.

[caseyriley]

I liked this video a lot, because you're not only providing useful "in the moment" information, like how to set custom options - But also explaining how that ties into the nix ecosystem... how its interpreted, and WHY/how that changes your configs evaluation, such that everything else has to be wrapped in the config attribute set.

Things like that make a massive difference in adding to my understanding of what's actually going on.

[ibrahimKaraagac]

Very nice series of videos. Thank you for doing this!

[jasonkirkham]

Not a programmer. New to Nix. This series is great!

[DreamsAPI]

Love your videos, you are a great teach ie explaining everything thoroughly and how different components connect to each other.

Would love to see videos going through source code and explaining and teaching and building awesome stuff
😃

[PieterPrinsloo]

You are doing the Lords work here. Thanks for these vids. I am using these as my primary source to setup my Nixos config coming from just having a single home-manager setup

[jylpah]

Maybe one thing you could have mentioned in this video is how to do string concatenation in Nix. But great video again.

[abelgerli]

The context how to use modularity is very important to manage your settings for the settings that are important to you. The context shows how to use the nix programming language in real use cases that can benefit development as well als corporate as home lab environments. 😊
Showing the modularity with NixOs on a rasberry Pi and a x64 architecture could show that the work of modularity pays of big time in heterogenous NixOS environments.
As a proxmox user i would love to see debian replaced as a base distro some day. But right now we should use NixOS to share our configurations without hazzle.

[XoStefan]

Love the content. Helped me understand a lot.

But literally sounds normal at 1.25x 😂

[petrtzurnazarov]

Amaizing, Thank you so much! Questioin: what is the browser you are using in the video when browsing github 11:25 ?

[hitarthpatel]

hello Librephoenix i love to see a video on nixos neovim config as there are many ways configuration nvim on nix but i cant find the a reliable way to do so and there are things like nixvim but dot hove support of lazy . i would love to see how you manger your nvim config, i know you use Emacs and your primary editor .

[mars_]

how did you get qutebrowser top open in the terminal?

[bonfireatnight]

There is one thing that confuses me ever since I've started reading up on NixOS. We write this system configuration file. The file defines a lambda expression. That is, if we would import the file manually, we would have to provide an attribute set with the arguments for the function parameters. As return value we would receive an set whose attributes Nix "understands".

Now, of course this is not what we actually do. We run `nixos-rebuild` based on the content of this file. So, where to the arguments for the parameters come from?

Until watching your videos I thought that the input `config` value comes from the _previous_ system generation. I thought it was there to make aspects of the _coming_ configuration depend on how things previously were. However, after your video I suspect things are much more... circular?!

Take the example where packages are installed based on the Window Manager that is to be used. In `if config.<...>` gets its value from the _output_, doesn't it? I mean, it asks whether _in the configuration we are currently defining_ we will use this or that window manager?

Something about this I find very confusing. I guess it works somehow because of the lazy property of the Nix language. Still, would this mean that I wouldn't be able to produce the output if I removed `config` from the inputs? And would this mean that this wouldn't work because the output couldn't be its own input anymore?

Anyway, thanks very much for your great videos! With every new production things are gradually making more sense.

[FreshSmog]

I honestly couldn't find a list of lib.types besides your blog post. Reading source code isn't very friendly for sure.

[biscotty]

If-then-else in nix is like the ternary operator in scripting languages.

[davidjeters]

How would something like this work if you were using startx and wanted to switch between two window managers such as awesome or xmonad? How would you pass an option to change both the xinitrc and the window managers?