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What Is Nix?

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Re: What Is Nix?

#101

Post by throwaway894345 »

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…

For a long time, Python3 support was advertised and there were lots of Python3 flags, but it was patently broken and there were many tickets that acknowledged as much. Allegedly that has changed now, but my experience was so bad I ran from it.

Re: What Is Nix?

#102

Post by austinl »

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 through the nix-shell. This makes builds on local machines and CI very easily reproducible. It also means that when dependencies change, we just update our nix config, and the new dependencies will automatically be fetched for all of our engineers and CI machines — no need to manually re-run the setup script.

This is my favorite part of Nix — you can do `nix-shell --run ""`, and it will make sure you have all of the correct dependencies (downloading if necessary), then run the command with those exact dependencies. This is especially magical when engineers working on other platforms have conflicting dependencies — a problem we no longer need to worry about.

Re: What Is Nix?

#103

Post by throwaway894345 »

mehrdadn wrote: post #76
throwaway894345 wrote: post #50

Earlier quoted context omitted.

> the DockerFiles themselves can also describe a reproducible process This is true, but Docker does almost nothing to support reproducibility. As soon as you do an apt-get, reproducibility goes out the window. > they are certainly "incremental" due to caching Caching is layer-based. Docker has no awareness of whether or not a particular dependency has changed or what is necessary to rebuild it. Docker only understand…

Great description, thanks. Question: do you know how Nix deals with language package managers (like pip)? If I do sudo pip install (leaving aside the usual debate as to its merits), does that then wreck my Nix install, especially if it happens to contain another version of the same package? And does it instantly make things non-reproducible again (just like the apt-get issue you mentioned)? Or does Nix somehow get ar…

Nix doesn't pay any attention to the rest of your system. It keeps everything it needs (including its own Python interpreter) in its own "nix store" directory, at /nix/store. You can crudely think of it as having its own virtualenv for every distinct Python target you use.

Re: What Is Nix?

#104

Post by takeda »

dataflow wrote: post #2

I'm still confused. What is Nix? Is it an OS, or a package manager? From the looks of it it's a package manager that I should be able to use it on any POSIX system, but I doubt that's the case?

Nix really is a purely functional, lazily evaluated language that is great at expressing dependencies in your project. You can think of it as a make on steroids, but it is much more than that.

Because the language expresses what to build from a known state (i.e. nothing is installed) together with its purely functional properties, means that for the same input (source code, dependencies, configuration options, system architecture etc) it supposed to always generate the same output.

Nix can be think of as package manager, and its nix-env command (which BTW is discouraged from Nix purist to use[1]) behaves like a package manager, but IMO it's more of a build system.

After the author of Nix wrote his thesis he mentioned that the language can describe an entire operating system. That's how NixOS happened. You can have a single configuration file that describes what needs to be installed on your OS how configured etc. The great thing is that you can take such configuration file, and recreate another machine with it configured exactly as you want it. No need for chef/salt/ansible etc. It actually has an edge over these tools, for example if you tell that specific package needs to to be installed, and than later you remove the package from the config, nix will remove that package as well (with chef/salt/ansible, you would need to add a state that's uninstalling the package), another benefit is that all changes are atomic, you either have your changes applied or nothing is changed, there's nothing in between (this makes things like replacing X11 with Wayland, or KDE with Gnome just another change, that you can always revert).

It's a very powerful tool, and the more I use the more amazing it seems. It shows that if you target specific problems the right way a lot of common headaches are eliminated.

[1] it's advisable to never install packages by hand using nix-env, since that adds mutability to your system, instead you should use nix-shell (another great tool) to temporarily make specific application available, use the global configuration.nix to install packages globally on the system, or use home-manager extension which allows you to configure each home directory (that means what dot files do, but also each user can have their individual packages, and goes further, for example you can even control what extensions firefox should have installed)

Re: What Is Nix?

#105

Post by throwaway894345 »

paul_milovanov wrote: post #81
throwaway894345 wrote: post #50

Earlier quoted context omitted.

> the DockerFiles themselves can also describe a reproducible process This is true, but Docker does almost nothing to support reproducibility. As soon as you do an apt-get, reproducibility goes out the window. > they are certainly "incremental" due to caching Caching is layer-based. Docker has no awareness of whether or not a particular dependency has changed or what is necessary to rebuild it. Docker only understand…

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.

It's worth noting that the bugs aren't evenly distributed across language plugins. Bazel might be solid if you're writing Java or something.

Re: What Is Nix?

#106

Post by mzaccari »

WatchDog wrote: post #74
illumin8 wrote: post #70

Earlier quoted context omitted.

I've had the (dis)pleasure of working with several projects that have been built by developers that have religion around Nix. These projects were contract work where the client paid a significant amount of money, and the final product was really poor quality. One of them is a financial application that has strict security requirements, so having a reproducible build system and some of the other qualities of Nix sound…

I haven't used Nix, but I would have thought that builds would be fast, due to how cache-able the dependencies should be.

We've been using Nix for deploying a Rails app for an enterprise customer for quite a few years now. One area where it shines for us is the ability to build it on relatively recent version of Ubuntu and deploy to a (almost EOL) RHEL6 box. Bundling, assets and various other tasks take just a few minutes. We also have ~20 Go services that are also deployed via Nix, and building takes seconds.

However, it can be quite cumbersome to get a Nix expression to the point where it builds reliably for something that takes multiple steps like a Rails app, especially if you're building on macOS and deploying to Linux. It's come a _long_ way in recent years, but with Enterprise customers now embracing containerization we migrated everything to that and haven't looked back.

Re: What Is Nix?

#107

Post by geofft »

mehrdadn wrote: post #85
geofft wrote: post #73

Earlier quoted context omitted.

> Say I happen to install package X via apt and Y via nix, and both of them depend on Z (in apt and nix respectively), and Z needs to bind to a port, then I imagine both will install but one of them will break. When you install a package with apt, rpm, etc., it has the ability to run code at install time, create init scripts/systemd unit files, etc. When you install a package with Nix, it does not have that ability.…

Thank you! Your comments are always great. :) Especially this bit was I think the insight I was looking for: > This does mean that the experience of using Nix is different from using a traditional package manager - you'll need to take care of starting the services you need, etc. I was trying to figure out where exactly the trade-offs would be -- so that's one of them: it seems like (in some sense, to simplify) Nix ta…

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 in your package, including the specific version of ssh you depend on)

If you want to upgrade sshd and the config changes, you'd make my-sshd-config 2.0, and nix would put its files in /nix/store/efgh5678-my-sshd-config-2.0/etc/ssh_config. You could have both of these installed at the same time.

Then, it's up to you to stop the sshd running out of my-sshd-config 1.0 and to start the one running out of my-sshd-config 2.0. Once you're confident of the upgrade, you can then tell Nix to clean up my-sshd-config 1.0, but that's just removing files, since you've already stopped the service.

(We're about to upgrade sshd at work next week and I wish we had something like this, honestly, both so I could distribute the files to machines well before the upgrade and so that it's easy to roll the upgrade back - just stop the new sshd and start the old one. Then there wouldn't be concerns about config drift, forgetting to revert files, etc. The only configuration that I'd have to manage is which one is active.)

Most people who use Nix without NixOS aren't running services like sshd out of it, but NixOS will do basically this for handling service upgrades. Conceptually NixOS gives you one mutable configuration knob, which is "what is all the systemwide stuff for this system." You can depend on some particular sshd and its config, some particular init system and its config, some particular syslogd and its config, etc. If you want to change any config, you make a new package with the changed config, and then flip the one mutable thing to point to it instead. (This does mean that it's easy to roll back your system to an old state if you realize you made a mistake!)

There is a limitation here, which is that Nix can't do a lot about config in your home directory, like ~/.ssh/ssh_config (for the SSH client). You'll have to be careful with that just like you would with upgrades in general. Alternatively, you could make your own Nix packages that include client config, and avoid storing config in your home directory.

Re: What Is Nix?

#108

Post by mehrdadn »

throwaway894345 wrote: post #101
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…

For a long time, Python3 support was advertised and there were lots of Python3 flags, but it was patently broken and there were many tickets that acknowledged as much. Allegedly that has changed now, but my experience was so bad I ran from it.

It's probably better than when you used it now, but it might depend on what you're trying to do (e.g. Cython has more room for improvement).

Re: What Is Nix?

#109

Post by matthewbauer »

_hl_ wrote: post #26
exdsq wrote: post #12

Earlier quoted context omitted.

You can use it on WSL1 and WSL2 but you can't use it natively on Windows. I used it on WSL2 just this afternoon and it was seamless but that makes sense because WSL2 is basically just a Linux VM anyway.

Although I don't see why it wouldn't work on Windows natively. Sure, it would probably need a complete reimplementation to replace all the POSIX stuff with Windows stuff, but fundamentally it ought to be possible?

The biggest issue IIRC is that Bash doesn't play well with Windows. Things like paths are handled different enough to cause lots of breakage. We could rewrite all of the Bash in Perl or Python, which has better cross-platform support, but that's a lot of work.

That said, there have been attempts to get native Windows support:

https://github.com/volth/nix-windows/commits/windows

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