Overview of the NixOS Linux distribution: Difference between revisions

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{{Expansion|Incomplete (reason: ~~(for now~~, ~~just converting~~ the ~~Incomplete category~~ to ~~this flag/template~~))}}

{{Expansion|Incomplete (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.

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 ==

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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]].

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);

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=== Declarative Configuration ===

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~~.

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>, or using <code>nixos-rebuild</code>'s <code>-I</code> option to override the <code><nixos></code> [https://nix.dev/manual/nix/latest/language/constructs/lookup-path.html#lookup-path lookup path]); 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. Most users keep the configuration files under <code>/etc/nixos</code> in a version control system such as Git.

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.

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# (hardware-configuration.nix is autogenerated upon installation)

# paths in nix expressions are always relative the file which defines them

imports =

imports = [

[

./hardware-configuration.nix

./my-dev-tools.nix

./my-desktop-env.nix

./etc.nix

];

# Name your host machine

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# Define user accounts

users.~~extraUsers =~~

users.users.myuser = {

{

extraGroups = [ "wheel" "networkmanager" ];

myuser =

isNormalUser = true;

{

};

extraGroups = [ "wheel" "networkmanager" ];

isNormalUser = true;

};

# Install some packages

environment.systemPackages =

environment.systemPackages = with pkgs; [

with pkgs;

ddate

[

testdisk

ddate

];

testdisk

~~zsh~~

];

# Enable the OpenSSH daemon

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==== 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.

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-24.05</code>. For more information on channels and how to choose them, see the [[Channel branches]] article.

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:

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=== 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.

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}

</nowiki>}}

{{file|etc/nixos/blog.nix|nix|<nowiki>

{{file|/etc/nixos/blog.nix|nix|<nowiki>

{

services.nginx.virtualHosts."blog.example.com" = {

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</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 ==

* [[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.

@@ Line 1: / Line 1: @@
-{{Expansion|Incomplete (reason: (for now, just converting the Incomplete category to this flag/template))}}
+{{Expansion|Incomplete (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 &mdash; including the [https://en.wikipedia.org/wiki/Linux_kernel kernel], installed [https://en.wikipedia.org/wiki/Package_manager packages] and system configuration files &mdash; 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 &mdash; including the [https://en.wikipedia.org/wiki/Linux_kernel kernel], installed [https://en.wikipedia.org/wiki/Package_manager packages] and system configuration files &mdash; 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.
-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 ==
@@ Line 11: / Line 11: @@
 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);
@@ Line 26: / Line 26: @@
 === Declarative Configuration ===
-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.
+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>, or using <code>nixos-rebuild</code>'s <code>-I</code> option to override the <code>&lt;nixos&gt;</code> [https://nix.dev/manual/nix/latest/language/constructs/lookup-path.html#lookup-path lookup path]); 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. Most users keep the configuration files under <code>/etc/nixos</code> in a version control system such as Git.
 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.
@@ Line 41: / Line 41: @@
      # (hardware-configuration.nix is autogenerated upon installation)
      # paths in nix expressions are always relative the file which defines them
-     imports =
+     imports = [
-         [
+         ./hardware-configuration.nix
-            ./hardware-configuration.nix
+        ./my-dev-tools.nix
-            ./my-dev-tools.nix
+        ./my-desktop-env.nix
-            ./my-desktop-env.nix
+        ./etc.nix
-            ./etc.nix
+    ];
-        ];
      # Name your host machine
@@ Line 60: / Line 59: @@
      # Define user accounts
-     users.extraUsers =
+     users.users.myuser = {
-        {
+      extraGroups = [ "wheel" "networkmanager" ];
-            myuser =
+      isNormalUser = true;
-            {
+    };
-                extraGroups = [ "wheel" "networkmanager" ];
-                isNormalUser = true;
-            };
-        };
      # Install some packages
-     environment.systemPackages =
+     environment.systemPackages = with pkgs; [
-            with pkgs;
+      ddate
-            [
+      testdisk
-                ddate
+    ];
-                testdisk
-                zsh
-            ];
      # Enable the OpenSSH daemon
@@ Line 96: / Line 88: @@
 ==== 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.
+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-24.05</code>. For more information on channels and how to choose them, see the [[Channel branches]] article.
 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:
@@ Line 145: / Line 137: @@
 === 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.
@@ Line 167: / Line 159: @@
 }
 </nowiki>}}
-{{file|etc/nixos/blog.nix|nix|<nowiki>
+{{file|/etc/nixos/blog.nix|nix|<nowiki>
 {
    services.nginx.virtualHosts."blog.example.com" = {
@@ Line 222: / Line 214: @@
 </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 ==
 * [[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.