12mo ago

Nix/Silverblue users: How big is the advantage if you already have 100% automated your deployments via Ansible?

There is a similar question on the site which must not be named.

My question still has a little different spin:

It seems to me that one of the biggest selling points of Nix is basically infrastructure as code. (Of course being immutable etc. is nice by itself.)

I wonder now, how big the delta is for people like me: All my desktops/servers are based on Debian stable with heavy customization, but 100% automated via Ansible. It seems to me, that a lot of the vocal Nix user (fans) switched from a pet desktop and discover IaC via Nix, and that they are in the end raving about IaC (which Nix might or might not be a good vehicle for).

When I gave Silverblue a try, I totally loved it, but then to configure it for my needs, I basically would have needed to configure the host system, some containers and overlays to replicate my Debian setup, so for me it seemed like too much effort to arrive nearly at where I started. (And of course I can use distrobox/podman and have containerized environments on Debian w/o trouble.)

Am I missing something?

54 comments

In this comparison, the devil is in the detail.
With Ansible, you have an initial condition onto which you add additional state through automatically executed steps dictated by you until you (hopefully) arrive at a target state. This all happens through modification of one set of state; each step receives the state of the previous step, modifies it and passes the entire state onto the next step. The end result is not only dependant on your declared steps but also the initial state. A failure in any step means you're left in an inconsistent state which is especially critical for the case of updating an existing state which is the most common thing to do to a Linux system.
In NixOS, you describe the desired target state and the NixOS modules then turn that description into compartmentalised bits of independent state. These are then cheaply and generically combined into a "bundle"; wrapping them into one big "generation" that contains your entire target state.
Your running system state is not modified at any point in this process. It is fully independent, no matter what the desired system is supposed to be. It is so independent in fact that you could do this "realisation" of the NixOS system on any other system of the same platform that has Nix installed without any information about the state of the system it's intended to be deployed on.
This "bundle" then contains a generic script which applies the pre-generated state to your actual system in a step that is as close to atomic as possible.
A good example for this are packages in your PATH. Rather than sequentially placing the binaries into the /usr/bin/ directory as a package manager would when instructed by ansible to install a set of packages, NixOS merely replaces the bin symlink with one that points at an entirely new pre-generated directory which contains the desired packages' binaries (well, symlinks to them for efficiency). There cannot possibly be an in-between state where only some of the binaries exist; it's all or nothing. (This concept applies to all parts that make up a Linux system of course, not just binaries in the PATH. I just chose that as an easy to understand example.)
By this property, your root filesystem no longer contains any operating system configuration state. You could wipe it and NixOS would not care. In fact, many NixOS users do that on every boot or even use a tmpfs for /.
(Immutability is a property that NixOS gains almost by accident; that's not its primary goal.)
- Very good explanation. It's an often overlooked property of NixOS and why I often feel like Nix on other systems is an okay way to get packages but you're missing out on all the good stuff you get through the modules, like losing 95% of what makes the concept good.
  I don't think NixOS is the best possible solution to the problem, but it's the only original distribution that even tries to tackle it instead of just working around it.
  
  it’s the only original distribution that even tries to tackle it instead of just working around it.
  Well, apart of GUIX of course ;)
  It's sort of a conceptual fork of Nix but the actual implementation is all original.
- Nice, thank you very much for this great summary!
  In my own words, you describe the difference between declarative vs. imperative configuration and the joy of atomic updates. :-)
  I just want to add one point: Theoretically I totally agree, that one might have a bad state in Ansible and the updated state is spoiled, and of course configuration drift is a theoretical problem via Ansible. In practice I never run into this problems in 10+ years of using Ansible. (Of course I treat servers/desktop as cattle, so every major revision of Debian means a complete/clean new installation.)
  
  If it works for you, that's great.
  I find it a lot more convenient to treat every change about my system as a nearly complete/clean new installation though and NixOS allows you to do so. An upgrade between major versions becomes a walk in the park due to this; it's the M.O. The last one didn't require any modification of the config on my NAS. I remotely rebuilt the system from my MacBook Pro with the new channel, rebooted to get the newer kernel and everything worked just like before.

I would separate NixOS from other immutable distros. NixOS is really about giving you blank slate and letting you fully configure it.
You do that configuration using a static config language that is able to be far more idempotent than Andible. It’s also able to define packages that are well contained and don’t require dynamic linking setup by manually installing other packages.
Immutable distros, on the other hand, really have no advantage to your setup and will probably feel more restrictive. The main use I see for them is for someone new or lazy that wants to get a working system up and running quickly.
- My favorite example of how idempotent NixOS is has to do with the DE. If you've ever looked at switching from gnome to KDE, or the other way around, most distros suggest to just re-install because each DE leaves so much cruft around and it's so hard to remove everything in a safe manner.
  With NixOS, you just change one line in your config, and the DE is cleanly swapped.
  
  Or you can add specialisations, which to be fair might require a reboot (system accounts might change during specialisations switch which will confuse the script trying to reload services for the now non-existent user) but it is how I have multiple DEs installed without their applications flooding the other ones, each with their own login manager (SDDM for plasma, gdm for gnome, greetd for sway).
- Well maybe you youself are too new to recognize some of the appeals ;)
  One large advantage with silverblue is, that the whole composition of the OS does not take place on the target machine. That means that all the issues that could arise will not take place on the target machine, and can be dealt with beforehand. In the simple case this could mean just enjoying vanilla silverblue without having to think about possibly borking the machine. In an advanced usecase this could mean for example building the os images in a GitLab CI/CD pipeline (with well working tooling that exists already for docker etc), then having automatic tests in the pipeline ensure that everything important works as expected. And only if the tests pass, the image will be added to the repositorie's image registry, where the target machines will fetch it from automatically and rebase to it.
  
  No, I fully understand it. But if you build the whole system where every package is isolated, none of the packages interfere with each other, and every package is tested across a wide array of architectures, you can just as safely put together your ideal OS setup and don't have to deal with being locked into very simple and bare system.
  The right place for immutable OSes is if you're using it as a server for container workloads, where you will never customize the base system. Or if you never want to customize your system. Yes, you can customize the system image, but it breaks all the guarantees that the images gives you because the packages themselves are not isolated and by bumping a wrong dependency for a custom packages you can still break the whole system.
- Thanks, that clarified things for me. Only thing I really would love to have are atomic updates, but for this I probably could just use BTRFS snapshots.
  
  Already has that. And if you use flakes, you can fully lock down your package versions that way the install is 100% identical on every machine no matter when you run it.

Everyone here have already explained their various stances very eloquently and convincingly - so I won't argue against that - so instead I'll just put forth my own 2c on why I use Silverblue instead of Nix/Ansible.
The main draw for me in using Silverblue (well, uBlue to be exact) is the no-cost, cloud-based, industry-standard, CI/CD and OCI workflow. Working with these standard technologies also helps me polish up my skills for work, as we've started to make use of containers and gitops workflows, so the skills that I'm gaining at personal level are easily translatable for work (and vice-versa).
With Nix (the declarative way), I'd have to learn the Nix language first and maintain the non-standard Nix config files and, tbh, I don't want to waste so much time on something that no one in the industry actually uses. Declarative Nix won't really help me grow professionally, and whilst I agree it has some very unique advantages and use-cases, it's completely overkill for my personal needs. In saying that, I'm happy with using Nix the imperative way though - I don't need to learn the Nix language, and it's great having access to a vast package repository and access my programs without having to go thru the limitations of containers.
As for Ansible, I'd have to have my own server (and pay for it, if it's in the cloud), and spend time maintaining it too. And although we use Ansible at work as well, so the skills I gain here won't be waste of time, it's unfortunately too inflexible/rigid for my personal needs - my personal systems are constantly evolving, whether it is in the common packages I use, or my choice of DE (my most recent fling is with Wayfire) etc. With an Ansible workflow, I'd be constantly editing yaml files instead of actually making the change I want to see. It's overkill for me, and a waste of time (IMO). You could argue that I'm already editing my configs on Github with uBlue, but it's nowhere as onerous as having to write playbooks for every single thing. And as I mentioned, I like to maintain some flexibility and manual control over my personal machines and Ansible will just get in the way of that.
With the uBlue workflow, I just maintain my own fork on Github with most of my customisations, + a separate repository for specific dotfiles and scripts that I don't want to be part of my image. Pull bot keeps my main uBlue repo in sync with upstream, and I only need to jump in if there's some merge conflicts that cannot be resolved automatically. At the end of it all, I get a working OCI image, with a global CDN and 90 days of image archives, allowing for flexible rollback options - all of this without incurring any costs or wasting too much time on my part. Plus I can easily switch between different DEs and OCI distros, with just a simple rebase - I could go from a Steam-Deck like gaming experience (Bazzite) to a productivity-oriented workstation (Bluefin), or play around with some fancy new opinionated environments like Hyprland and River (Wayblue) - all with just a simple rebase and a reboot, without needing to learn some niche language or waste time writing config files. How cool is that?

Ansible must examine the state of a system, detect that it is not in the desired state and then modify the current state to get it to the desired state. That is inheritently more complex than building a immutable system that is in the desired state by construction and can not get out of the desired state.
It's fine as ,one as you use other people's rules for ansible and just configure those, but it gets tricky fast when you start to write your own. Reliably discovering the state of a running system is surprisingly tricky.

Another aspect I like about Nix compared to what I understand from Ansible (which I used a bit but not much) is that your configuration describes your system without any hidden state. Yes, you only get your dependencies through full evaluation, but what I mean is this: Let's say you install something on a system, i.e. you add it to your list of packages, which you later remove. To my knowledge, Ansible won't remove the package if not explicitly asked. However, if you explicitly tell Ansible to not have it installed, what happens if that package is later introduced as a dependency?
Ansible will always operate on a stateful system, which is kind of the combination of what others have already mentioned – it's (EDIT: it being Nix) idempotent and there's no hidden state that will break something down the way.
- Ansible works on tasks, and to your hypothetical there, if you have a task that calls the package manager to put a package in the state 'absent', but it is another package's dependency, it will have little to do with ansible, and just follow the package manager's behaviour. (Up to some details. Like for 'apt', ansible runs the command with '-y', which has a little different behaviour than just removing the interaction part and assuming yes). If the package manager removes the depending package, and your playbook has first a task that installs it, then a taks that removes the dependency, you will always get 'changed' on both tasks everytime you run the playbook, even if your playbook puts the machine in the same state as before.

I use Fedora Silverblue and in my experience the updates are very stable. But with Debian and Ansible automation I think you are not missing a much, maybe nothing at all.
Would you mind sharing how you automated your setup with Ansible or generally how to use Ansible in that way? I use some bash scripts for my automation and it is a bit hacky, so if I could improve that, it would be nice.
- The thing about ansible is to always remember that it really is just a backup python script that gets copied to your server and executed. Yes it works quite well, but you have to be careful to not have break on you.
  For me the difference to nix is, that my bud expression will actually always produce the same output or tell me it can't. Instead of ansible which will fail after some updates went past.
- Yes, I really love the Silverblue download in the background, reboot and you are up to date updates. So much better than watching the package manager do its thing. :-)
  I don't know about your knowledge about Ansible, and when you are already running Silverblue and are happy with it, it might be more worthwhile for you to explore how to automate Silverblue and the containers you are using... and write a blog post for people like me, how you did it, so I can learn. :-P
  Ansible... basically it allows you to install software with the package managers (apt, dnf, ...), configure/restart etc. services, clone git repositories, run arbitrary commands, configure stuff with dconf.
  Example for my workflow:
  When Debian 12 got into the alpha stage, I simply set up a virtual machine, install git, ansible and vim, and then I start from a known starting place (like Gnome Desktop for desktops, minimal for servers). First, I clone my git repository with my dotfiles, and link all the relevant dotfiles. After that I simply use Ansible to install all packages I will use from that distribution, run dconf to configure Gnome for my needs, configure/download software from 3rd party package repositories or just download tarballs and install them to /opt or ~/opt. Of course also flatpaks can be configured/downloaded via Ansible.
  Once, everything works great in the virtual machine I will work in the VM for a few days or even weeks. If everything works stable I'll just make a clean install of the operating system, add some hardware specific tweaks (change grub config, tweak WIFI drivers power mode) and then I am up and running. Thanks to Debian, my Ansible configs are mostly stable with minor tweaks for around 2 years, and when time is due for Debian 13, I'll repeat the cycle.
  The way I do things with Ansible have grown for a long time and are tailored to my private/professional use cases. I simply like having the same setup on every desktop/server I deploy, because I never have to wonder, if my software is configured in the way I like it, if a hotkey works or if something I use is installed or not. (And if my hardware dies or I do an SSD upgrade, I am up and running within minutes, same is true if I get new hardware.)
  Still, it is a tradeoff. I really like Fedora, but one year of updates is too short for me and my initial investment to setup a new version of Debian. Further, I only use dconf based desktops like Mate or Gnome, because I can simply configure them painless 100% via Ansible. OTOH I have MY Debian desktop setup running on multiple AMD64 and AARCH64 physical and virtual machines. If I want to experiment with software, I just create a VM, start Ansible, get a cup of tea and I have a disposable machine to play around. Further I have my setup 100% documented, if I wonder, what strange power settings tweak I needed in which file to make Debian 11 work on my netbook, I know were to find the 100% correct answer..
  Excuse the wall of text, hope that gave you an idea, don't hesitate to reach out if any questions are left. Obviously, you have to decide for yourself if such a setup is worthwhile for you. In case you use only one Desktop, this would be total overkill. :-P
  
  Reading this, I find myself really, REALLY wanting to replicate that sort of setup, especially the docs part which is something I've been neglecting. I always say to myself, "The next Arch install, I'll document the setup" and it never happens!
  
  Thank you for this in depth answer. It makes me want to explore Ansible and setup automation. Sounds really great!
  and write a blog post for people like me, how you did it, so I can learn.
  I am thinking about that ... 🤔

Silverblue doesn't solve the same problems as Nix, or Ansible for that matter. I built my own in the past and it was non-trivial - although the CI process could pair quite nicely with Ansible. IMHO the primary advantage of Silverblue is that updates are a download, with practically zero work to do after the download has completed (this is a very big deal for RPM-based systems because an update boot can take a long time).
As for Ansible vs Nix, try switching from one program to another across all your machines. It's doable but not fun. Now try switching back across all your machines. Nix makes your system equal a configuration, it does not add configuration.

I switched from a big custom Ansible deployment to NixOS.
The system includes 8 managed machines, multiple VPNs and a custom certificate authority.
Downsides:
rethinking of how to manage Certificates and VPN configs outside of Nix
getting secrets to work took a bit until I found agenix
deployments can take a while with deploy-rs
Still, I can only tell you how much more at ease I feel with the NixOS based system. Its just much easier to refactor, not having to take care of legacy cleanup and polluting the machines over time.
Once you wrap your head around it all more complex system architectures start to become manageable/maintainable.
IaC
You still need sth like Terraform on the side for your actual infrastructure provisioning.
Solutions to bridge this with the Nix ecosystem are evolving in the nix-community repos on Github, but I found it easier to manage that separately for the time being.
All in all I would recommend NixOS based systems for the heavy lifters in your setup. If you want to deploy a fleet of machines you are entering new territory. Exciting, but maybe too much of a time commitment for some.

OP, can you link to your desktop configuration using Ansible? How do you use it?
- Sorry, I have only Ansible files at work which I cannot share and my private Ansible setup is in a private git repository. I elaborated further down in another comment my workflow.
  My suggestion is to forget about best practices (like roles) for private desktop setup, simply start with a task file and a fresh installation of your favorite distro inside a virtual machine. From that starting point, everything you do to configure the VM you do via Ansible. Want to set the hostname? Learn about ansible.builtin.hostname, want do install a package? Use ansible.builtin.apt, ansible.builtin.dnf or similar, want to harden your sshd config? Look at ansible.builtin.lineinfile, ansible.builtin.copy or ansible.builtin.template ... Screwed up your VM? Replace it with a new one, run your Ansible tasks and continue were you left off...
  Hope that helps!
  
  Thanks. I use Ansible myself, but I was more interested in how I would run Ansible on my daily driver, from my daily driver.

I appreciate this is more asking about nicks, but I’ll offer some feedback on my experience with immutable distributions more generally.
I took an adventure into silver blue and micro OS recently and I was completely unimpressed. It’s a novel idea from a good place, but it was the most incoherent and buggy experience I’ve ever had on Linux distribution in the past 10 years. Nothing walked reliably, and everything broke, I also found that trying to use anything other than the default gnome desktop was an exercise in futility.
I need to clarify, I think it’s a great idea. In practice though, Both implementations, silver blue and micro OS, are really over engineered.
I have adapted the ideas into my current install and I achieve the same thing with A/B Snapshots And a script that takes me from a base snapshot to my daily driver. Everything else exists in containers So bootstrapping up only involves half a dozen packages (iwd, node, nvim etc. ).

I think you have arguments about MicroOS (or Silberblue, which I know less about, and possibly Nix, which I know nothing about, and it seems to me it is not in the same group) wrong. Take a look at this https://youtu.be/lKYLF1tA4Ik.
- Here is an alternative Piped link(s):
  https://piped.video/lKYLF1tA4Ik
  Piped is a privacy-respecting open-source alternative frontend to YouTube.
  I'm open-source; check me out at GitHub.

I wonder now, how big the delta is for people like me: All my desktops/servers are based on Debian stable with heavy customization, but 100% automated via Ansible.
Close to none. Immutable solve the same problem that was solved years ago with Ansible and BTRFS/ZFS snapshots, there's an important long-term difference however...
Immutable distros are all about making thing that were easy into complex, “locked down”, “inflexible”, bullshit to justify jobs and payed tech stacks and a soon to be released property solution. We had Ansible, containers, ZFS and BTRFS that provided all the required immutability needed already but someone decided that is is time to transform proven development techniques in the hopes of eventually selling some orchestration and/or other proprietary repository / platform like Docker / Kubernetes does. Docker isn’t totally proprietary and there’s Podman but consider the following: It doesn’t really matter if there are truly open-source and open ecosystems of containerization technologies. In the end people/companies will pick the proprietary / closed option just because “it’s easier to use” or some other specific thing that will be good on the short term and very bad on the long term.
“Oh but there are truly open-source immutable distros” … true, but again this hype is much like Docker and it will invariably and inevitably lead people down a path that will then require some proprietary solution or dependency somewhere (DockerHub) that is only required because the “new” technology itself alone doesn’t deliver as others did in the past. Those people now popularizing immutable distributions clearly haven’t had any experience with it before the current hype. Let me tell you something, immutable systems aren’t a new thing we already had it with MIPS devices (mostly routers and IOTs) and people have been moving to ARM and mutable solutions because it’s better, easier and more reliable.
The RedHat/CentOS fiasco was another great example of this ecosystems and once again all those people who got burned instead of moving to a true open-source distribution like Debian decided to pick Ubuntu - it’s just a matter of time until Canonical decides to do some move.
Nowadays, without Internet and the ecosystems people can’t even do shit anymore. Have a look at the current state of things when it comes to embedded development, in the past people were able to program AVR / PIC / Arduino boards offline and today everyone moved to ESP devices and depends on the PlatformIO + VSCode ecosystem to code and deploy to the devices. Speaking about VSCode it is also open-source until you realize that 1) the language plugins that you require can only compiled and run in official builds of VSCode and 2) Microsoft took over a lot of the popular 3rd party language plugins, repackage them with a different license… making it so if you try to create a fork of VSCode you can’t have any support for any programming language because it won’t be an official VSCode build. MS be like :).
All those things that make development very easy and lowered the bar for newcomers have the dark side of being designed to reconfigure and envelope the way development gets done so someone can profit from it. That is sad and above all set dangerous precedents and creates generations of engineers and developers that don’t have truly open tools like we did.
This is all about commoditizing development - it’s a negative feedback loop that never ends. Yes I say commoditizing development because if you look at it those techs only make it easier for the entry level developer and companies instead of hiring developers for their knowledge and ability to develop they’re just hiring “cheap monkeys” that are able to configure those technologies and cloud platforms to deliver something. At the end of the they the business of those cloud companies is transforming developer knowledge into products/services that companies can buy with a click.
- Who hurt you?
  I mean, you got some points, but went way over board with it and beyond the scope of the question.
  but someone decided that is is time to transform proven development techniques in the hopes of eventually selling some orchestration and/or other proprietary repository / platform like Docker / Kubernetes does.
  So, you really think, that this must be the reason immutable desktops were invented?
  
  So, you really think, that this must be the reason immutable desktops were invented?
  Most likely not, but the people pushing for the / the narrative certainly are for that.
- We had Ansible, containers, ZFS and BTRFS that provided all the required immutability needed already but someone decided that is is time to transform proven development techniques
  Just so you know, NixOS is older than all of these, actually. And for that matter, no less flexible.
- I don’t know of anyone with a modicum of experience with cloud solutions that would pretend it is making anything “simpler” lol
  The only closed parts of Docker are Docker Desktop, which isn’t required at all, and Docker Hub, which is a repo like any other. You can load images from anywhere. It’s hard to take anything you say regarding container technology seriously if you seriously think VMs & Ansible/Chef/Puppet really answers the same problems as lightweight containers.
  MS did take some language servers and relicensed them, yes. Other language servers still exist, and the LSP protocol is still open, and used in many other editors.
  This reads like “Real Programmers Don’t Use Pascal”, minus the tongue in cheek tone…
  
  You just missed the point. There are always alternatives, generally not as good and unlike before all tooling is now hostage of some big provider.
- Sorry, hard disagree from me.
  Immutable distros solve a lot of problems and are IMHO a great idea. I love my SteamDeck with SteamOS, I really like Silverblue and OpenSUSEs MicroOS (Avalon or however it is called right now). For my desktops/servers Debian is the best choice right now, but my Thinkpad from 2012 which runs now happily as an entertainment machine is a perfect example where an immutable distro would be much better and practical.
  Immutable distros are a solution to a real problem, and this problem is not solved by Ansible/BTRFS etc. Hell, I'll happily jump ship sooner than later. Of course, YMMV and I don't say immutable distros solve all problems for everyone, but having this option is great IMHO.
  
  Well I tried Aeon for a month and it has been the least reliable system I’ve used since, well actually probably anything, like maybe vista I guess.
  The thing is a mess and it brings nothing to the table over A/B snapshots.
  The scales must be different for enterprise use because I’d never go near another immutable OS again after this terrible experience.
  Maybe it’s just flatpak that’s unreliable on Aeon, I found moving electron apps into podman containers was a lot better. But on void it was fine, clearly a lot more work to do the flesh it out I goes.
  Tbf SB had far less issues than Aeon.
  
  Immutable distros are a solution to a real problem, and this problem is not solved by Ansible/BTRFS etc.
  Just tell me what that problem is and how it isn't already solved with Ansible/BTRFS.

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