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Could someone summarise what is the advantage of NixOS compared to something like Ansible or Saltstack + any other Linux distribution?

tbenst 7y ago
I used a Ansible for years before switching to NixOS. The problem with ansible is it is an imperative configuration tool that makes efforts to be declarative, but is not fully. Most runs fail to be declarative, eg even something as basic as “apt update” is irreversible. Ultimately, Ansible requires you to write code that is (State, Code) -> New State, whereas NixOS is truly Code -> State
jordanbeiber 7y ago
NixPkgs amongst other things replace rpm/deb packages - and having a package install declared in a git repo is awesome compared to installing a pre-packaged compressed blob. Nixos keeps the entire system state based on a declaration and lets you move back/forward on whole system configurations super quick. Ansible and salt does not really declare a complete system state but rather try to manipulate the underlying system. Ansible keeps no state at all actually. Nixos+pkg is all about declaring and keeping a state of a machine as much as reasonably possible. It has it’s flaws but the end result is still much more coherent and predictable compared to traditional configuration management.
takeda 7y ago
It's similar n some way, but totally rethinking the problem. Ansible or saltstack are essentially programs that configure your system in specific way. Ansible takes more of a list of things what to change and how, while saltstack tries to be declarative. NixOS is essentially a Linux system described using Nix language. Whenever you make change and run nixos-rebuild, as name suggests it actually rebuilds your entire system from scratch, it is just smart enough to not do work that was already done. Benefits of it is that you will always get to the same state no matter what. Another benefit that is quite annoying with saltstack/ansible if you remove specific application/service/whatever once you rebuild the system, it is gone, like it was never there. You also get Nix benefits, nix never leaves anything in half state changes are atomic, either they are applied successfully or not, if a change broke something, you can easily rollback. Things like for example changing KDE to Gnome or replacing Xorg with Wayland is no harder than replacing emacs with vim (or vim with emacs, if I upset you). The way how Nix works allows different packages using even conflicting libraries. For example you can have two applications using different openssl version etc. If you have one application and you need to apply a custom patch to it or maybe even use a different version. In traditional OS good sysadmins would create a custom RPM package an install it. In Nix you just override the definition, and if a cached build is not available, Nix will be smart enough to compile the code (this means no need for artifactory and uploading custom packages there, though to prevent recompiling every time, you should set up a caching server (there's also caching as a service option if you don't want to manage it) or you can even use S3 bucket. Basically Nix and NixOS is rethinking how building/deploying/packaging does it offers many benefits, CMS like ansible/saltstack/chef/puppet/cfengine etc are no longer needed. It can be used for having comon developement environment, can be used for building, ci/cd etc.

tbenst 7y ago

I used a Ansible for years before switching to NixOS. The problem with ansible is it is an imperative configuration tool that makes efforts to be declarative, but is not fully. Most runs fail to be declarative, eg even something as basic as “apt update” is irreversible. Ultimately, Ansible requires you to write code that is (State, Code) -> New State, whereas NixOS is truly Code -> State

jordanbeiber 7y ago

NixPkgs amongst other things replace rpm/deb packages - and having a package install declared in a git repo is awesome compared to installing a pre-packaged compressed blob. Nixos keeps the entire system state based on a declaration and lets you move back/forward on whole system configurations super quick. Ansible and salt does not really declare a complete system state but rather try to manipulate the underlying system. Ansible keeps no state at all actually. Nixos+pkg is all about declaring and keeping a state of a machine as much as reasonably possible. It has it’s flaws but the end result is still much more coherent and predictable compared to traditional configuration management.

takeda 7y ago

It's similar n some way, but totally rethinking the problem. Ansible or saltstack are essentially programs that configure your system in specific way. Ansible takes more of a list of things what to change and how, while saltstack tries to be declarative. NixOS is essentially a Linux system described using Nix language. Whenever you make change and run nixos-rebuild, as name suggests it actually rebuilds your entire system from scratch, it is just smart enough to not do work that was already done. Benefits of it is that you will always get to the same state no matter what. Another benefit that is quite annoying with saltstack/ansible if you remove specific application/service/whatever once you rebuild the system, it is gone, like it was never there. You also get Nix benefits, nix never leaves anything in half state changes are atomic, either they are applied successfully or not, if a change broke something, you can easily rollback. Things like for example changing KDE to Gnome or replacing Xorg with Wayland is no harder than replacing emacs with vim (or vim with emacs, if I upset you). The way how Nix works allows different packages using even conflicting libraries. For example you can have two applications using different openssl version etc. If you have one application and you need to apply a custom patch to it or maybe even use a different version. In traditional OS good sysadmins would create a custom RPM package an install it. In Nix you just override the definition, and if a cached build is not available, Nix will be smart enough to compile the code (this means no need for artifactory and uploading custom packages there, though to prevent recompiling every time, you should set up a caching server (there's also caching as a service option if you don't want to manage it) or you can even use S3 bucket. Basically Nix and NixOS is rethinking how building/deploying/packaging does it offers many benefits, CMS like ansible/saltstack/chef/puppet/cfengine etc are no longer needed. It can be used for having comon developement environment, can be used for building, ci/cd etc.