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What Is Nix?

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Re: What Is Nix?

#221

Post by takeda »

enriquto wrote: post #21
throwaway894345 wrote: post #17

Earlier quoted context omitted.

This is because Nix needs to express a lot more so builds are reproducible and incremental. Docker doesn’t care about these things.

Even if Docker doesn't really care about this, the DockerFiles themselves can also describe a reproducible process, and they are certainly "incremental" due to caching (not sure of what you mean by "incremental"). Does nix power merit such a big compromise against simplicity and readability?

Dockerfiles are as reproducible as a bash script (and that's not a hyperbole). Yes, they are incremental but as you pointed out it is per statement.

This requires:

1) that it is on you to specify the correct order 2) you are limited to 42 layers 3) it doesn't work well even if you know what to do and care about it:

- in most setups that I've seen once you trigger build system it still starts from scratch (for example each time, docker images pull all dependencies again and again every build). nix build won't build stuff that was already done, unless you explicitly instruct it with --check option

- typically people use `COPY . .`, because it is less work, but in reality certain files need to be pulled earlier than others, but then you're more likely to run into layer limit, also it's more work, more prone to errors (like typos, forgetting about a file etc). With declarative configuration, nix will only rebuild derivations where input changed. It doesn't matter what order you specify dependencies.

> Does nix power merit such a big compromise against simplicity and readability?

The simplicity causes complexity everywhere else. Is this really that complex? Here's for example everything that's needed to build pgbouncer[1] (you can ignore the meta section, that's informational only). I'm using that since I used it recently.

Nix actually isn't a complicated language, just different. I believe the big problem people are having is just different programming paradigm, but the programming paradigm used by nix is really what is needed to solve the problem correctly (purely functional -> for the same inputs (source code, dependencies, system etc) you always get the same output; lazily evaluated -> build only things you actually depend on). The properties of the language allow to define how to build specific program in a declarative way.

[1] https://github.com/NixOS/nixpkgs/blob/master/pkgs/servers/sq...

Re: What Is Nix?

#222

Post by austinl »

lilyball wrote: post #206
austinl wrote: post #102

We're using Nix where I work as well, and while I can say it was not the most user-friendly to set up, once we got it in place it has reliably worked for the last two years. We used to have a long and flaky shell script which set up the development environment for new engineers and CI machines (for iOS development on macOS, specifically). Now we have a very simple script which just installs nix and runs alls builds t…

By this do you mean developers doing local builds still run their builds at the command-line via nix-shell and don’t ever build from Xcode directly? That sounds very awkward.

Not at all — you can control what commands are actually executed when developers hit the play button or do ⌘+B/⌘+R in Xcode. Xcode is fundamentally just an IDE, even though we forget that sometimes since it's traditionally coupled so tightly with xcodebuild.

Re: What Is Nix?

#223

Post by singron »

mehrdadn wrote: post #114
geofft wrote: post #107

Earlier quoted context omitted.

So, there is no /nix/etc - anything in /nix is immutable. I haven't done this and hopefully someone will correct me if I get the details wrong, but I think the way you'd make this work within nix is you'd make your own package, let's call it "my-sshd-config," and it depends on a certain version of sshd. Then you'd have /nix/store/abcd1234-my-sshd-config-1.0/etc/sshd_config. (where "abcd1234" is a hash of everything i…

Oh dear... so you have to write a Nix package (and learn how the language and package management work) just to modify global config files, instead of just editing them? That sounds like an absolute nightmare for a local machine, though possibly a great tool for automated systems. Also, if there's no /nix/etc... then what is Nix modifying? sshd (or any other more common program; I'm just using sshd as an example to un…

NixOs manages configuration in a really elegant way with modules. Modules are a structured way of combining different sources of configuration.

E.g. you might need to configure a list of users on the system. You might manually configure your user in your top-level module:

  users = [ "dataflow" ];
But if you have postgres enabled, then it might configure a user in it's own module.

  users = [ "postgres" ];
When the modules are evaluated and combined, you can end up with a list that contains both:

  users = [ "postgres" "dataflow" ];
Compare this to conventional distros. If you edit your distro's default config file, and the distro updates the default config file, how will your modified config be updated? E.g. Arch just puts the new config in a .pacnew file, and you will just keep using your old config. pacman prints a line out, but it often scrolls off the top of the screen and it's easy to miss. It's up to you to manually merge those configs now. E.g. my arch system has 22 .pacnew files in /etc, and occasionally things break or don't work as well because updates aren't applied to the configs. Debian has debconf, but that always seemed more like a set of ad-hoc workarounds than a solution.

Re: What Is Nix?

#224

Post by takeda »

prox wrote: post #37
kdtsh wrote: post #5

Earlier quoted context omitted.

Nix is a package manager. NixOS is an OS which includes the Nix package manager. My understanding is that a feature of Nix is you can declare an OS (I.e. declare the collection of configurations and software etc for an OS) which Nix will process to provide you with an OS called NixOS.

So it processes the config file (and thus all needed packages) one time or does it process it every time you boot?

Whenever you run `nixos-rebuild switch` a symlink is created for `/run/current-system` which is the current system. That's what is used on every boot until another change (you also have an option in boot loader to boot into prior versions (it is just a symlink))

Re: What Is Nix?

#225

Post by takeda »

yachtman wrote: post #205

A company I worked at embraced nix. Beforehand I was a big docker fan and had few issues with it (yes there were occasionally caching issues and damn it docker figure out the issue with hyperkit on mac os, but largely its a productive tool). From an outside perspective nix just felt like alot more work, and nearly no one (except the people that set it up) could ever get it to work. So basically the entire build proce…

Out of curiosity, any reason why you didn't want to understand it? You spent time learning docker, why this was different?

Re: What Is Nix?

#226

Post by zelly »

I like the idea of Nix. It's definitely the future of package management and build systems. But it's solving a problem we knew how to solve in the 80s: dependency hell is solved by statically linking everything. In fact in the Windows world it's still like this. If you need OpenSSL, for example, it should be in your source tree and compiled in the same build pipeline as your application.

Re: What Is Nix?

#227

Post by takeda »

downerending wrote: post #91
tomberek wrote: post #86

Nix is a powerful package manager. I can confidently compile and run multiple incompatible versions of software simultaneously. I can build projects from years ago. I can package large projects from different ecosystems (python 2/3, c/c++, go, javascript) and be confident they will not interfere with each other. I can try bleeding edge software with no risk to it interfering with my system. It is faster and less hass…

As an example, what's minimally required to run two different versions of program-x from the command line. Can I do something like this easily? cat-8.22 /etc/passwd | cat-8.3 -A

tomberek gave you example how to do it, although I think in real life you probably won't need to do something like this. Much more common situation is having two programs that depend on conflicting version of a library. You get this often if you start including custom repos into your system, because you need specific version of something. Sometimes you make that application work, but then you break something else.

Docker is often pitched to solve this, you get one application in one docker, and another in another. Since docker isolates and pretends to have 2 different operating systems it kind of allows this to happen, but that's hacky.

Nix solves this correctly. Instead of having some central place listing what libraries are installed on the system, it actually every component listed in an unique path. This way application A can use library X and application B can use library Y even when X and Y are different versions of the same library. What's more, is that the derivations in nix can be extended like objects in OO class. You can easily modify application A to use library Y and B to use library X. And if such build is not available in cache Nix will know how to rebuild it (no need to worry about having compiler and libraries installed).

Re: What Is Nix?

#228

Post by takeda »

Ericson2314 wrote: post #96
genr8 wrote: post #69

Stumbled upon NixOS yesterday and today its frontpage, 1st link. Same thing happened with OpenBSD the day before. Whats tomorrow, Qubes? I wonder what the chances of coincidence are if I investigate one new OS per day. https://www.foxypossibilities.com/2018/02/04/running-matrix-... https://en.wikipedia.org/wiki/NixOS

No tomorrow could be BSD and Nix https://github.com/NixOS/nixpkgs/pull/82131

Oh nice, thanks for doing the work.

Re: What Is Nix?

#229

Post by singron »

mehrdadn wrote: post #94
paul_milovanov wrote: post #81

Earlier quoted context omitted.

Bazel is buggy?! Bazel is not a clone, it's the refactoring of the internal build system, basically. I am 99% certain that Blaze currently has Bazel at the core. And it's pretty damn robust.

Bazel is definitely buggy. One of the silliest ones is this one (and as far as this one goes, I do not understand how this issue exists when Blaze has been used in Google for such a long itme): https://github.com/bazelbuild/bazel/issues/9419 One of the more fundamental bugs is this one: https://github.com/bazelbuild/bazel/issues/4558 I've even had to clean --expunge and clear my disk cache to fix some build errors be…

As far as bazel bugs, it's safe to say that if you stick to the ways that Google uses blaze, then you are unlikely to run into bugs. E.g. Google doesn't run blaze on windows or use system toolchains, so it makes some sense that those are where the issues are. Unfortunately, Google also uses their own rules, so the rule quality for open source rules varies somewhat since they haven't all been battle tested in the same way. blaze and the Google codebase have also co-evolved for like 15 years to work nicely together, whereas anything adopting bazel today might be an awkward 3rd wheel for a while.

Disclosure: Ex-Googler

Re: What Is Nix?

#230

Post by mehrdadn »

singron wrote: post #229
mehrdadn wrote: post #94

Earlier quoted context omitted.

Bazel is definitely buggy. One of the silliest ones is this one (and as far as this one goes, I do not understand how this issue exists when Blaze has been used in Google for such a long itme): https://github.com/bazelbuild/bazel/issues/9419 One of the more fundamental bugs is this one: https://github.com/bazelbuild/bazel/issues/4558 I've even had to clean --expunge and clear my disk cache to fix some build errors be…

As far as bazel bugs, it's safe to say that if you stick to the ways that Google uses blaze, then you are unlikely to run into bugs. E.g. Google doesn't run blaze on windows or use system toolchains, so it makes some sense that those are where the issues are. Unfortunately, Google also uses their own rules, so the rule quality for open source rules varies somewhat since they haven't all been battle tested in the same…

Yeah, I've figured as much in hindsight. It'd have been nice if they were more forthcoming about this than leaving it as a surprise for everyone to figure out (including, now, for the parent to whom I replied).
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