I tried out nixos (the complete distro based on nix) on the weekend -- it's not saying too much that it's a revelation. I can see myself completely switching for my development machines and possibly for servers as well.

The amazing thing is that the whole set up of your linux machine is encaptulated in one declarative text file (that you can put in version control). Give it a try by installing it using VirtualBox: https://nixos.org/wiki/Installing_NixOS_in_a_VirtualBox_gues.... You can log in (demo/demo in the 14.10 vm) and play around, essentially be editing `/etc/nixos/configuration.nix`.

I recommend trying the configuration of an experienced user. Here's the result of a simple search on github:

https://github.com/sitano/configuration.nix

https://github.com/Hinidu/configuration.nix

https://github.com/garbas/nixos-configuration

You can also get started very easily using a ec2 tiny instance (free tier): https://nixos.org/wiki/NixOS_on_Amazon_EC2

Awesome to see this here! I've been using Nix/Nixos (which Guix is heavily based on) on my personal laptop for several months now. I'll never look back from the purely declarative system configuration - I finally feel like I have full control of my machine's state.

It looks like Guix provides a significantly more expressive interface with Scheme than Nixos does with Nix expressions. IIRC, there's also better integration with the system (Nixos auto-generates plenty of bash), which will surely accelerate development / debugging.

Does anyone here have Guix experience to share?

Everyone talks about advantages. Would love to hear about disadvantages. Not obvious ones (like having to learn configuration language semantics or package missing stuff myself), but things that don't lie down in a plain sight right away and only discovered after a few days, weeks or months of usage.

Anyone to share their experiences?

(Migrating from Arch to NixOS at the moment, but thought maybe I'd detour a bit and try Guix.)

Version 0.8.1 of GNU's purely functional package manager Guix has been released.

The project develops, at the same time, GNU GSD (Guix System Distribution), a GNU operating system.

GNU GSD is an avant-garde GNU system utilizing Guix as its package manager, and the similarly Guile/Scheme based dmd as its init system.

Could someone explain in a simple way, why this is better that using, for example, apt-get ?

We are going to use Guix as a package manager on a bioinformatics cluster. Managing various different scientific applications at different versions with very different dependencies for different user groups is something that is incredibly painful with traditional packaging systems. Guix greatly simplifies this whole process and writing package definitions in Scheme is so much nicer than, say, writing RPM spec files.

To try the downloaded USB image in VirtualBox, first decompress the .xz file and then run

    vboxmanage convertfromraw ~/Downloads/gsd-usb-install-0.8.1.i686-linux gsd-install.vdi --format vdi

The resulting VDI file can then be attached to a VirtualBox machine as a primary IDE disk. Be sure to enable PAE/NX in the System settings.

It seems that Guix&Nix have many advantages. Could anyone also elaborate some disadvantages of this system in comparison with traditional package managers like debian's or rpm? [Edit] I'm considering a switch to one of Guix or Nix, and I'd like to know if the pros outweigh the cons.

Nix and Guix begin to have some momentum, it's a joy to see. I'm now wondering if that momentum will revive.. Hurd development. That's right, I said it.

It’s great to see a new release!

From my understanding, the biggest disadvantage to purely functional package management is that you can't just swap out a package in isolation when many others depend on it. If I upgrade a package, I have to upgrade its whole DAG of dependent packages if I want them to use the new version (I could however delay that; they would simply continue to use the old version which hasn't been garbage-collected yet because they still use it).

So lots and lots of compilation (on build farms at least), and lots of bandwidth usage. Though something like ccache can help with the compilation, and binary diffs could help with the bandwidth.

Immutable data structures in FP are probably a good analogy.

Edit: argh, this was supposed to be a reply to the question about the disadvantages of the purely functional package managers specifically, not the OS in general.

    jabberwork-1.2
      jabberwock.core-1.6
      jabberwock.apache.interface-0.3
    
    jabberwock-1.3
      jabberwock.core-1.6
      jabberwock.apache-interface-0.4

The learning curve is pretty steep. It's not just a new config language, it's also letting go of many preconceptions one may have (where stuff lives on the filesystem e.g.).

That's also true for software I'm packaging. Certain ecosystems just really love to load configuration files and write log files relative to the binary path which breaks in nixos because all packages live on a read-only mount (looking at you ruby, cargo from rust will also be fun).

Lastly there's just not the same number of contributors yet so you're going to have more of the small issues that get fixed and reported by the armies of users that e.g. Ubuntu has.

I'm saying all this as an incredibly happy user. I can think of few technologies that have given me as much leverage as nixos in recent years.

A disadvantage is that some services (like dbus) look for service files in a well-known location. When packages are installed they don't place any of their files in a directory outside of their target directory. So, JACK2, for example, won't be able to place its dbus service file in a location that the dbus service natively knows about.

In many cases situations like this can be fixed by setting environment variables, but in some cases more patching is required to make this work properly.

EDIT: I don't consider this a serious disadvantage, though. It is not unusual for packagers to patch software in other distributions. (I dare you to check out spec files for popular RPMs.) It's just something a package maintainer has to think about under some circumstances.

I should also note that I'm surprised at how little patching is required for most software (besides the common shebang patching).

1. There are few packages, compared to dpkg.

2. It creates guix-specific users for building purposes.

There really isn't much bad to say about guix. You can even switch to it without giving up on your old package manager. That way, even point 1. isn't an issue. Of course, 2. isn't really an issue in itself; `cat /etc/passwd` already contains a lot of users whose purpose I know little about.

Guix is based on Nix, so the following applies to both.

apt-get allows at most one version of a package to be installed at a time; if you want two versions, you need to ask the maintainers to split the package into two. Guix doesn't suffer this problem; packages are given an ID based on a hash of their contents and dependencies, so two versions will happily sit side-by-side. An "update" is treated more like installing a separate package.

If two applications depend on two different versions of some library, you can't install both applications. In Guix you can, since each can use the version it needs.

apt-get affects the whole system. All users are affected by a change; if some other user installs/removes/updates a package, you have to just deal with it. In Guix, every user gets a "profile" package, which can depend on anything they like. Installing/removing/updating packages just creates a new version of your profile, with its dependencies added/removed/changed according to what you asked for.

apt-get is stateful: the contents of /usr, /etc, etc. are changed as packages are installed/removed. Guix is immutable: packages live in their own read-only directories, so nothing can break them after installation.

apt-get can't roll back: packages can't be down-graded, all kinds of actions are taken by pre/post install scripts which can't be undone, etc. Since Guix is immutable, "rolling back" just means going back to the old selection of packages; ie. installing the old version of the profile package.

Both Guix and Nixos allow your system to be defined declaratively. This means that the details of reproducing your system state, given a declarative configuration, are fully handled by Guix/Nixos. So, if you like, you can consider the mapping between declarations and systems a pure function (i.e. you always get the same startup state for a given config). It's not hard to see how this could be valuable when deploying many servers (reproducability), getting out of dependency hell / failed upgrades (perfect rollbacks), bug reporting (just append the config that fully describes your system!), etc...

I've also found that the increasing entropy caused by stateful alternatives (e.g. apt-get) eventually becomes impossible to manage. This is entirely due to hidden state that grows in complexity over time. Eventually, things break in a way that nobody on StackOverflow has seen before, and you're SOL. In the declarative world, everything specific to your setup is required to be defined upfront, in one central place. This provides you with a much better chance of understanding your system as it evolves.

(Your account name makes me think you've appreciated functional programming data structures at some point. In not surprisingly, the benefits of immutability and declarative style in programming languages seem to carry over to configuration management.)

Others have explained it, but I like to see it like that:

- apt-get, yum, pacman and "traditional" package managers deal with _transition of your system_: _please install this packet_, _please remove this packet_

- nix and guix deal with _state of your system_: _please make sure that the final state is thus_.

This brings easy reproducibility of a system (if you have the recipe, you can have a another machine be an _exact_ copy) and de-entanglement (no more managing conflicting dependencies, no more dangling files). If I were to draw parallel, it would be like this:

- "traditional" package managers are like jQuery: you pick some DOM node / some package, and modify it / update it. After some time you don't know anymore who modified this DOM node, who needs it, ... things become hard to track

- nix and guix are like React: you specify the state you want in a single place (or rather in a definite place) and React/nix maps that definition into your final product

Here's a long blog post that goes into more detail: https://www.domenkozar.com/2014/03/11/why-puppet-chef-ansibl...

apt-get can not install the same package/software in many different versions, there is always some package conflicts happening and you cant describe the state of your desired system with any "apt-get" language. You must script your desired state manually or use puppet or chef or whatever, which will perform the steps/tasks that you desire on your system using multitude of software and languages.

With guix gsd and nixos, the package manager is the configuration manager. The package manager is not just package manager, its not just apt-get, it is also puppet/chef/salt, and a distribution-maker or manager. I believe with guix you could make your own distribution (software collection) in the same descriptive language as making packages. You cant do that with apt or any debian tools.

Don't know about Guix, it seems to be inspired by/similar to Nix. As far as I understand, the advantage of Nix is that it's a stateless description of the system, so the advantages are:

* you can describe a tree of dependencies using any version of the package you want, and can easily rollback to a previous tree if an update broke it

* because you describe a tree of packages, you're actually describing the complete state of the system, there's no leftovers from previous installations which make it work by chance

* as a result you can easily partially alter (and rollback) or move nix configurations from one machine to the next

Essentially nix (and guix?) merges package management and configuration management in a stateless and declarative, easily audited and customised, manner.

It's better because given the same input you always get the same output. For example, in Gentoo when one builds a package the final result depends on what's been built before. Or (killer feature for configuration management):

Suppose one has a resource for file in Puppet

file "blah" do source "yada" end

if you erase that resource, the file still stays there. With Nix/Guix anything not defined in configuration isn't present at all on system.

Another feature : one can install, for example, different versions of Python/PyPy/etc locally using the same package manager. Local and system-wide package share the same underlying files and don't interfere.

Rollbacks, very easy way to restore system packages/configs to previous working state.

Very interesting your responses. Looks interesting to try it. So it's hard / too problematic to get it working over, a Kubuntu ?