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My First Impressions of Nix

mtlynch.io

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Re: My First Impressions of Nix

#21

Post by FpUser »

I have shell script with bunch of common functions to simplify particular tasks and then main script that when ran installs all needed packages, creates / copies various config files, pulls my C++ code from repo and builds my servers and installs those as daemons. It also installs cron jobs that execute backups / replication. It is smart enough to skip already performed steps and can safely run multiple times. It can run on Debian, Ubuntu, Arch and Mint.

It is fast and reliable and can deploy new infra and or restore state of that from backup. I use it for years without any problems.

Re: My First Impressions of Nix

#22

Post by politelemon »

seqizz wrote: post #17
p-e-w wrote: post #13

I've occasionally encountered projects using Nix, and I've casually browsed the Nix and NixOS websites, but I still don't have a clear idea of what Nix is. Is it a package manager? A build system? An operating system? A container platform? A sandbox? An automation tool? Which widely used, existing software tools is it analogous to?

Afaiu it's trying to become all. Nix is on core, you can get packages from nixpkgs / write your own definitions, use it on OS configurations via NixOS, use its built-in helpers to run your containers with it, make a whole CI and cache it with the help of Hydra etc.

That's confusing because NixOS also seems to be an operating system, looking at the blog post?

Re: My First Impressions of Nix

#23

Post by hamandcheese »

p-e-w wrote: post #13

I've occasionally encountered projects using Nix, and I've casually browsed the Nix and NixOS websites, but I still don't have a clear idea of what Nix is. Is it a package manager? A build system? An operating system? A container platform? A sandbox? An automation tool? Which widely used, existing software tools is it analogous to?

Most of the above.

- Nix is a tool for building and installing software.

- Nix is a language for expressing how to build a package. Nix-the-tool reads expressions defined in Nix-the-language to know what to do. At the end of the day, this translates into normal commands that run in a sandboxed build environment.

- Nixpkgs is a monolithic repository of 80000+ packages, defined literally as one giant expression in the Nix language (this works fine because Nix is an extremely lazy language). This also includes lots of helpers and abstractions for building packages that can be handy in your own projects. It is possible to use Nix-the-tool without Nixpkgs, but nobody does.

- NixOS is a Linux distribution built on these foundations. Everything under /etc is built from nix expressions. You can not directly edit these. Mostly NixOS is about building systemd unit files from Nix expressions - viewed through that lens it's not really all that exotic of an OS. NixOS has modules that make it very easy to configure and run lots of software.

Re: My First Impressions of Nix

#24

Post by microtonal »

hamandcheese wrote: post #8

> Nix, on the other hand, does have a concept of state. If you make a one-line change to a 200-line Nix configuration, it doesn’t have to re-do all the work from the other 199 lines. It can evaluate the state of the system against the configuration file and recognize that it just has to apply the one-line change. And that change usually happens in a few seconds. The author seems to have some misguided ideas about Nix…

Just to elaborate a bit for those not familiar to Nix (slightly simplified to exclude recent support for content addressing). Nix work with derivations, a derivation is basically a data structure that specifies how a package is built. Derivations are normally not created by hand but using a function (eg. stdenv.mkDerivation).

When you ask Nix to build a package, it hashes a normalized form of derivation data structure. This hash is useful in various ways, but one way it is used [1] is to look up whether the derivation is already in the Nix Store. Because if it is, there is no need to build it. So Nix looks up whether

    /nix/
exists. If it exists, the build is done. If it doesn't exist and you have a binary cache configured (which by default is the binary cache provided by the NixOS project), Nix will look up the derivation hash in the binary cache. If it exists in the binary cache, Nix will download the path to the local Nix store. After that

    /nix/
exists in the store and the build is done (without building anything). Only if that fails, Nix will actually build the derivation.

Now, one of the cool things about Nix is that it is derivations all the way down. So, it's not that just what we traditionally think of as packages is a derivation, but people wrap up all kinds of things as derivations, including configuration, etc. Since derivations are usually generated by functions, there are all kinds of useful functions that make derivations for eg.: single configuration files, scripts, etc.

In the end, building a NixOS system generation is just building a derivation. nixos-rebuild switches to a different generation by just setting a bunch of symlinks to an output path in the store containing that system generation (/nix/).

At any rate, when you make a one-line change to a 200-line Nix configuration, Nix does have state to keep track of what it needs to rebuild or not. Nix will just try to build the derivation (and its dependencies), but it hashes the derivations, finds that their output paths are already in the store.

Some might argue that then the store is state. But it's not, at build time you are evaluating a pure function with memoization (the Nix Store).

[1] There is also a package name and version in the store path, but lets keep it simple.

Re: My First Impressions of Nix

#25

Post by mindwok »

p-e-w wrote: post #13

I've occasionally encountered projects using Nix, and I've casually browsed the Nix and NixOS websites, but I still don't have a clear idea of what Nix is. Is it a package manager? A build system? An operating system? A container platform? A sandbox? An automation tool? Which widely used, existing software tools is it analogous to?

It's got elements of all of those things. It's basically a toolchain for building an 'environment', which is roughly analogous to a Linux distribution.

It starts with a language that lets you declare the desired state of your environment, including which packages are present and the configuration of those packages. The packages are installed and managed through the Nix package manager. The end result is an 'environment' that reflects the desired state you expressed. That environment can be a Docker image, an ISO, or it could be a running system you're booted into (in the case of NixOS). Or it can even be an ephemeral environment that exists on the filesystem of whatever distribution you're using (in the case of nix-shell). Each of these options offers different levels of isolation and reproducibility, depending on the requirements of your project or system.

There's lots of clever components that make something like this possible, and they're all wrapped up in the Nix umbrella.

Re: My First Impressions of Nix

#26

Post by CapsAdmin »

I feel a little lost on nixos. Been using it for a while now on my main personal desktop and it's fine, but whenever I want to do something like running a python project (ml based ones for example), or compile software from source, I'm lost because I don't know what I'm doing. Most projects target Ubuntu, so I feel you need to know a lot about how nix really works to get them compiling, which is often not what I'm in the mood for tinkering with when I just want to test something.

So in the end I end up using distrobox with Ubuntu which works surprisingly well, but feels very hacky as I'm supposed to try and use nix. The way I rationalize this is that I'll get rid of distrobox slowly over time as I learn how it works.

Re: My First Impressions of Nix

#27

Post by imagineerschool »

p-e-w wrote: post #13

I've occasionally encountered projects using Nix, and I've casually browsed the Nix and NixOS websites, but I still don't have a clear idea of what Nix is. Is it a package manager? A build system? An operating system? A container platform? A sandbox? An automation tool? Which widely used, existing software tools is it analogous to?

"Yes, it is."

AFAIK It's each of those things, each unfortunately named the same.

Re: My First Impressions of Nix

#28

Post by chpatrick »

politelemon wrote: post #22
seqizz wrote: post #17

Earlier quoted context omitted.

Afaiu it's trying to become all. Nix is on core, you can get packages from nixpkgs / write your own definitions, use it on OS configurations via NixOS, use its built-in helpers to run your containers with it, make a whole CI and cache it with the help of Hydra etc.

That's confusing because NixOS also seems to be an operating system, looking at the blog post?

NixOS is just a super barebones distro where everything is configured with Nix. You can also use Nix on Ubuntu or some other distro.

Re: My First Impressions of Nix

#29

Post by throwawayqqq11 »

wesapien wrote: post #14

Does anyone have any ideas on what the most likely outcome would be for NixOS losing the S3 bucket funding?

You propably have to pull all your sources from github and compile them yourself once, since there is no remote store that provides prebuild artifacts? (I dont know what use the S3 bucket/s is for.)

Re: My First Impressions of Nix

#30

Post by mindwok »

nittanymount wrote: post #6

planning to learn/use ansible, wonder if Nix is ready to use ? have most functions/features ?

If you're planning on using Ansible for your job or to administer Linux systems, then stick with Ansible. Nix is very niche and you aren't going to see much return on investment until adoption is significantly higher, and I'm not sure that will happen in its current state.

That being said if you want to learn Nix for its own sake or because it is awesome, which it is, then have fun!

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