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{{Expansion|Incomplete (reason: (for now, just converting the Incomplete category to this flag/template))}}
{{Navbox Nix}}
{{Expansion|reason=It needs to be an easy introduction, because its one of the first articles new users read here. Thats why it needs to be simplified a bit and more complex topics should be moved to other articles.}}


[https://nixos.org/ NixOS] is a Linux distribution based on the [[Nix]] package manager and build system. It supports [https://reproducible-builds.org/ reproducible] and [https://en.wikipedia.org/wiki/Declarative_programming declarative] system-wide [https://en.wikipedia.org/wiki/Configuration_management configuration management] as well as [https://en.wikipedia.org/wiki/Atomicity_(database_systems) atomic] upgrades and rollbacks, although it can additionally support [https://en.wikipedia.org/wiki/Imperative_programming imperative] package and user management. In NixOS, all components of the distribution — including the [https://en.wikipedia.org/wiki/Linux_kernel kernel], installed [https://en.wikipedia.org/wiki/Package_manager packages] and system configuration files — are built by [[Nix]] from [[Wikipedia:Pure function|pure functions]] called [[Nix Expression Language|Nix expressions]].
[https://nixos.org/ NixOS] is a Linux distribution based on the [[Nix]] package manager and build system. It supports [https://en.wikipedia.org/wiki/Declarative_programming declarative] system-wide [https://en.wikipedia.org/wiki/Configuration_management configuration management] as well as [https://en.wikipedia.org/wiki/Atomicity_(database_systems) atomic] upgrades and rollbacks, although it can additionally support [https://en.wikipedia.org/wiki/Imperative_programming imperative] package and user management. In NixOS, all components of the distribution — including the [https://en.wikipedia.org/wiki/Linux_kernel kernel], installed [https://en.wikipedia.org/wiki/Package_manager packages] and system configuration files — are built by [[Nix]] from [[Wikipedia:Pure function|pure functions]] called [[Nix Expression Language|Nix expressions]].


Since Nix uses [https://en.wikipedia.org/wiki/Executable binary] caching, this provides a unique compromise between the binary-oriented approach used by distributions such as Debian and the [https://en.wikipedia.org/wiki/Source_code source]-oriented approach used by distributions such as Gentoo. Binaries can be used for standard components, and custom-built packages and modules can be used automatically when a pre-built binary is not available.
Since Nix uses [https://en.wikipedia.org/wiki/Executable binary] caching, this provides a unique compromise between the binary-oriented approach used by distributions such as Debian and the [https://en.wikipedia.org/wiki/Source_code source]-oriented approach used by distributions such as Gentoo. Binaries can be used for standard components, and custom-built packages and modules can be used automatically when a pre-built binary is not available.


Stable NixOS releases are delivered twice a year. NixOS was created by [https://edolstra.github.io/ Eelco Dolstra] and [https://en.wikipedia.org/wiki/Armijn_Hemel Armijn Hemel], and initially released in 2003. It is community developed and maintained under the stewardship of the [https://nixos.org/nixos/foundation.html NixOS Foundation].
Stable NixOS releases are delivered twice a year (around the end of May and the end of November). NixOS was created by [https://edolstra.github.io/ Eelco Dolstra] and [https://en.wikipedia.org/wiki/Armijn_Hemel Armijn Hemel], and initially released in 2003. It is community developed and maintained under the stewardship of the [[Nix_Community#NixOS_Foundation|NixOS Foundation]].


== Installation ==
== Installation ==
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For a full installation guide, see the [https://nixos.org/nixos/manual/index.html#ch-installation Installation chapter of the NixOS manual]. This wiki also includes alternative or supplemental guides, such as [[NixOS as a desktop]].
For a full installation guide, see the [https://nixos.org/nixos/manual/index.html#ch-installation Installation chapter of the NixOS manual]. This wiki also includes alternative or supplemental guides, such as [[NixOS as a desktop]].


Most users will install NixOS via [https://nixos.org/nixos/download.html one of the ISO images.] Both "graphical" and "minimal" ISO variants are available for each supported architecture; the "graphical" images are suitable for users intending to install a desktop environment, and the "minimal" images are suitable for users intending to install NixOS in a server role or desiring a smaller ISO image. The ISO images are hybrid images which can be burnt to optical media or copied raw to a USB drive and booted as-is. See the installation guide for details.
Most users will install NixOS via [https://nixos.org/download/#nixos-iso one of the ISO images.] Both "graphical" and "minimal" ISO variants are available for each supported architecture; the "graphical" images are suitable for users intending to install a desktop environment, and the "minimal" images are suitable for users intending to install NixOS in a server role or desiring a smaller ISO image. The ISO images are hybrid images which can be burnt to optical media or copied raw to a USB drive and booted as-is. See the installation guide for details.


In addition to the ISO images, the [https://nixos.org/nixos/download.html download page] provides a number of alternative methods for installing NixOS. These include:
In addition to the ISO images, the [https://nixos.org/download/#nixos-iso download page] provides a number of alternative methods for installing NixOS. These include:


* Virtual appliances in OVA format (compatible with VirtualBox);
* Virtual appliances in OVA format (compatible with VirtualBox);
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Additionally, many existing Linux installations can be converted into NixOS installations using [https://github.com/elitak/nixos-infect nixos-infect] or [https://github.com/jeaye/nixos-in-place nixos-in-place]; this is particularly useful for installing NixOS on hosting providers which do not natively support NixOS.
Additionally, many existing Linux installations can be converted into NixOS installations using [https://github.com/elitak/nixos-infect nixos-infect] or [https://github.com/jeaye/nixos-in-place nixos-in-place]; this is particularly useful for installing NixOS on hosting providers which do not natively support NixOS.


For information on installing NixOS on various ARM devices, see [[NixOS on ARM]].
=== System architectures ===
NixOS provides out of the box support for most x86_64 devices, and generic ARM64 devices.


== Usage ==
==== 32-bit x86 architectures ====
Support for 32-bit x86 architectures (i.e. <code>i686</code>) has been declining. While most packages should still compile and run, their cache availability is significantly reduced<ref>https://discourse.nixos.org/t/limited-cache-availability-for-i686-32-bits-x86-architecture/37626</ref>. The 32-bit x86 ISO is no longer offered as a ready-built image, but it may still be built manually.


=== Declarative Configuration ===
==== 64-bit x86 architectures ====
Most <code>x86_64</code> devices should run NixOS without issues.


One of NixOS's most distinguishing features is the ability to ''declaratively configure'' the whole system. This is done by specifying a configuration file which specifies the entire system state, including which packages should be installed and all the various system settings and options. This configuration file is normally located at <code>/etc/nixos/configuration.nix</code> (although another location may be specified using the environment variable <code>NIX_PATH</code>); after the configuration file is modified, the new configuration is then made active by running <code>nixos-rebuild switch</code>. The switch is atomic and can be rolled back if necessary. The configuration files under <code>/etc/nixos</code> may even be kept in a version control system such as Git if desired.
==== 32-bit ARM architectures ====
{{Main|NixOS on ARM}}
NixOS isn't officially supported on ARM32 devices (e.g. <code>armv6</code> and <code>armv7l</code>), however, for some of these devices, there may be community support.


Conventional distributions require users to manually modify configuration files, but these changes are not tracked. If distributions change the default contents of configuration files, these changes often have to be manually merged by users if they have previously modified the file, or the distribution modifications may not be integrated at all, leading to undesired configuration drift. Configuration settings and changes are rarely recorded in a version control system. These shortcomings are often rectified after-the-fact if at all by configuration management solutions such as Puppet or Chef. These tools reconcile system configuration with a description of the expected state. However, these tools are not integrated into the operating system design and are simply layered on top, and OS configuration may still vary where an aspect of OS configuration has not been specified in the description of expected state.
==== 64-bit ARM architectures ====
{{Main|NixOS on ARM}}
As long as a device supports the generic systemd boot process, NixOS should run out of the box. However, specific devices with proprietary bootloaders may have issues running it.


By comparison, NixOS's declarative configuration system provides a fully integrated facility for OS configuration management. Failure to specify any given item of configuration results in that item having a well-defined state, rather than being allowed to drift unmonitored. Because the full system configuration is captured in the NixOS configuration system, this also makes NixOS highly suited to the automatic deployment of configuration in environments such as automated server farms; tools such as [[NixOps]] make this easy.
==== MIPS architectures ====
{{Main|NixOS on MIPS}}
There used to be limited support for MIPS architectures in NixOS, and remnants of this support may still be found in Nixpkgs. However, there is no official support.


Here is a simple example of a NixOS system configuration:
== Usage ==


{{file|/etc/nixos/configuration.nix|nix|<nowiki>
=== Declarative Configuration ===
{ config, pkgs, ... }:


{
One of NixOS's defining features is its declarative configuration model, where the entire system state — including installed packages, system services, and settings — is described in configuration files. The primary file is typically located at <code>/etc/nixos/configuration.nix</code>.
    # Import other configuration modules
    # (hardware-configuration.nix is autogenerated upon installation)
    # paths in nix expressions are always relative the file which defines them
    imports =
        [
            ./hardware-configuration.nix
            ./my-dev-tools.nix
            ./my-desktop-env.nix
            ./etc.nix
        ];


    # Name your host machine
Changes to the configuration are applied atomically using <code>nixos-rebuild switch</code>, ensuring reproducibility and the ability to roll back to previous states. Most users track their configuration files in a version control system, enabling consistent and portable system setups. These shortcomings are often rectified after-the-fact if at all by configuration management solutions such as Puppet, Ansible or Chef. These tools reconcile system configuration with a description of the expected state. However, these tools are not integrated into the operating system design and are simply layered on top, and OS configuration may still vary where an aspect of OS configuration has not been specified in the description of expected state.  
    networking.hostName = "mymachine";


    # Set your time zone.
Unlike conventional distributions, where system configuration is often scattered across manually edited files, NixOS integrates configuration management directly into the operating system. This eliminates configuration drift and makes NixOS particularly well-suited for automated, reproducible deployments.
    time.timeZone = "Europe/Utrecht";


    # Enter keyboard layout
For more details and examples on NixOS configurations, see [[NixOS system configuration]].
    services.xserver.layout = "us";
    services.xserver.xkbVariant = "altgr-intl";
 
    # Define user accounts
    users.extraUsers =
        {
            myuser =
            {
                extraGroups = [ "wheel" "networkmanager" ];
                isNormalUser = true;
            };
        };
   
    # Install some packages
    environment.systemPackages =
            with pkgs;
            [
                ddate
                testdisk
                zsh
            ];
    # Enable the OpenSSH daemon
    services.openssh.enable = true;
   
}
</nowiki>}}
 
For inspiration, a variety of NixOS configuration files made by community members can be found in the [[Configuration Collection]].


=== Imperative Operations ===
=== Imperative Operations ===
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==== Channels ====
==== Channels ====


NixOS, as well as Nix packages and NixOS modules are distributed through Nix channels: mechanisms for distributing Nix expressions as well as the associated binary caches for them. These channels are what determine which version of NixOS you are using, and they can be broadly categorized into ''stable'' and ''unstable'' channels, and ''large'' and ''small'' channels. Most users will want the stable/large channel, currently <code>nixos-21.11</code>. For more information on channels and how to choose them, see the [[Nix Channels]] article.
In the [[Nix ecosystem]], [[Channel branches|channels]] are a mechanism for distributing collections of [[Nixpkgs|Nix packages]] and [[NixOS]] module definitions. A channel represents a curated, versioned set of package definitions and system configurations, typically corresponding to a particular release or the latest available development state.
 
Like packages installed via <code>nix-env</code>, channels are managed at user-level. NixOS uses the channels set for the <code>root</code> user to update the system-wide configuration; channels set for other users control only the user environment for that user. If you wish to change the channel used by the system-level configuration (<code>/etc/nixos/configuration.nix</code>), ensure you run the correct <code>nix-channel</code> command as root:


{| class="wikitable"
When using channels, your system or [[User Environment|user environment]] pulls package definitions and options from a URL pointing to a specific snapshot of the Nix Packages collection (Nixpkgs) and associated NixOS modules.
|+ Common nix-channel commands
|-
|Listing current channels
|<code>nix-channel --list</code>
|-
| Adding a primary channel
|<code><nowiki>nix-channel --add https://nixos.org/channels/channel-name nixos</nowiki></code>
|-
| Adding other channels
|<code><nowiki>nix-channel --add https://some.channel/url my-alias</nowiki></code>
|-
| Remove a channel
|<code>nix-channel --remove channel-alias</code>
|-
| Updating a channel
|<code>nix-channel --update channel-alias</code>
|-
| Updating all channels
|<code>nix-channel --update</code>
|-
| Rollback the last update (useful if the last update breaks the <code>nixos-rebuild</code>)
|<code>nix-channel --rollback</code>
|}


Note that updating channels won't cause a rebuild in itself; if you want to update channels and rebuild, you can run <code>nixos-rebuild --upgrade switch</code> to do both in one step.
For more information on using and configuring nix channels, refer to [[channel branches]].


== Internals ==
== Internals ==
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=== Usage of the Nix store ===
=== Usage of the Nix store ===


A lot of confusion for newcomers arises from the fact that configuration is stored in the read-only <code>/nix/store</code> tree along with all the installed packages. This fact makes it impossible to manually edit system configuration; all configuration changes must be performed by editing the <code>/etc/nixos/configuration.nix</code> file and executing <code>nixos-rebuild switch</code>. NixOS provides the [[NixOS Modules System|modules system]] for editing all required configurations. Users should first use [https://search.nixos.org/options the option search tool] to check if the option they need exists before attempting to manually add files or configuration via low-level NixOS features like activation scripts.
A lot of confusion for newcomers arises from the fact that configuration is stored in the read-only <code>/nix/store</code> tree along with all the installed packages. This fact makes it impossible to manually edit system configuration; all configuration changes must be performed by editing the <code>/etc/nixos/configuration.nix</code> file and executing <code>nixos-rebuild switch</code>. NixOS provides the [[NixOS_modules|module system]] for editing all required configurations. Users should first use [https://search.nixos.org/options the option search tool] to check if the option they need exists before attempting to manually add files or configuration via low-level NixOS features like activation scripts.


The system purity makes it possible to keep system configuration in a central place, without the need to edit multiple files. This configuration can be distributed or version controlled as desired. It also provides for determinism; if you provide the same inputs, the same version of Nixpkgs and the same <code>/etc/nixos/configuration.nix</code> you will get the exact same system state.
The system purity makes it possible to keep system configuration in a central place, without the need to edit multiple files. This configuration can be distributed or version controlled as desired. It also provides for determinism; if you provide the same inputs, the same version of Nixpkgs and the same <code>/etc/nixos/configuration.nix</code> you will get the exact same system state.
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=== Modules ===
=== Modules ===


The NixOS module system as defined in  [[Nixpkgs]] provides the means necessary to customize the configuration of the OS. It is used to enable and customize services such as nginx, enable firmware and customize the kernel.
The [[NixOS modules|NixOS module system]] as defined in  [[Nixpkgs]] provides the means necessary to customize the configuration of the OS. It is used to enable and customize services such as nginx, enable firmware and customize the kernel.


All module configuration is generally performed by adding options to <code>/etc/nixos/configuration.nix</code>. Most of the examples in the wiki show how this file can be used to configure the OS.
All module configuration is generally performed by adding options to <code>/etc/nixos/configuration.nix</code>. Most of the examples in the wiki show how this file can be used to configure the OS.
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}
}
</nowiki>}}
</nowiki>}}
{{file|etc/nixos/blog.nix|nix|<nowiki>
{{file|/etc/nixos/blog.nix|nix|<nowiki>
{
{
   services.nginx.virtualHosts."blog.example.com" = {
   services.nginx.virtualHosts."blog.example.com" = {
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</syntaxHighlight>
</syntaxHighlight>


You can configure automatic garbage collection by setting the [https://search.nixos.org/options/?query=nix.gc nix.gc] options in <code>/etc/nixos/configuration.nix</code>. This is recommended, as it keeps the size of the Nix store down.
You can configure automatic garbage collection by setting the [https://search.nixos.org/options?query=nix.gc nix.gc] options in <code>/etc/nixos/configuration.nix</code>. This is recommended, as it keeps the size of the Nix store down.


== See also ==
== See also ==


* [[NixOS modules]], a library for modular [[Overview of the Nix Expression Language#Expressions|Nix expressions]] which powers [[#Declarative Configuration|the declarative configuration of NixOS]].
* [[NixOS modules]], a library for modular [[Overview of the Nix Expression Language#Expressions|Nix expressions]] which powers [[#Declarative Configuration|the declarative configuration of NixOS]].
* [[NixOS Testing library]], a library for creating reproducible infrastructure tests, based on [[Nixpkgs]], [[NixOS]], QEMU and Perl.
* [[NixOS VM tests]], a library for creating reproducible infrastructure tests, based on [[Nixpkgs]], [[NixOS]], QEMU and Perl.
* [https://github.com/ryan4yin/nixos-and-flakes-book NixOS & Flakes Book](Ryan4yin, 2023) - 🛠️ ❤️ An unofficial NixOS & Flakes book for Beginners.  
* [https://github.com/ryan4yin/nixos-and-flakes-book NixOS & Flakes Book] (Ryan4yin, 2023) - 🛠️ ❤️ An unofficial NixOS & Flakes book for beginners.  


[[Category:Pedias]]
[[Category:Pedias]]
[[Category:NixOS]]
[[Category:NixOS]]
[[Category:Nix]]
[[Category:Nix]]
Retrieved from "https://wiki.nixos.org/wiki/NixOS"