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Table of contents
What is NixOS?
History of NixOS
Key Concepts and Features of NixOS
Declarative System Configuration
Atomic Upgrades and Rollbacks
Isolation of Environments
Nix: How It Works?
Key Principles and Mechanisms
Practical Example
Frequently Asked Questions
What is the main advantage of NixOS?
Can I use Nix package manager without NixOS?
How is package isolation achieved in NixOS?
Last Updated: May 18, 2024

Nix Operating System

Author Gunjan Batra
0 upvote


The world of open-source operating systems is filled with various flavors and unique approaches, and among these stands out NixOS, an OS built on top of the Nix package manager. 

Nix Operating System

What is NixOS?

NixOS is a Linux-based operating system that uniquely leverages the Nix package manager. The Nix package manager introduces a declarative approach to package management, allowing for reliable system upgrades, rollbacks, and more. Unlike traditional package managers, Nix allows multiple versions of software to coexist without interfering with each other, thus solving the infamous "dependency hell".

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History of NixOS

NixOS is a Linux distribution that emerged from the creation of the Nix package manager by Eelco Dolstra in 2003 during his PhD research at Utrecht University. Officially released in 2008, NixOS showcased how an entire operating system could be managed using the principles of Nix, allowing for atomic upgrades and rollbacks. As developers and system administrators began to adopt NixOS, its community grew, contributing to its development and documentation.

A key feature of NixOS is its declarative configuration model, where users define the entire system state in a single configuration file, ensuring reproducibility and consistency. Over the years, tools like nixops for deployment and nixos-rebuild for managing system configurations have enhanced its usability. The NixOS ecosystem has expanded to include more software packages and support a wider range of hardware.

Today, NixOS is recognized for its reliability and flexibility, appreciated by users worldwide for creating reproducible and maintainable environments. Driven by a dedicated community, NixOS continues to evolve, adhering to its core principles of declarative configuration and reproducibility.

Key Concepts and Features of NixOS

Declarative System Configuration

NixOS utilizes a declarative model for system configuration. This means you describe your entire system - the software packages, system services, file systems, and other configurations in a single, coherent specification file /etc/nixos/configuration.nix.

For instance, to install the NGINX web server, you would simply add it to your configuration file:

services.nginx.enable = true;

After updating the configuration file, NixOS makes it so by running the nixos-rebuild switch command, aligning the system state with the specified configuration.

Atomic Upgrades and Rollbacks

Thanks to the immutable infrastructure paradigm used by Nix, system upgrades and configuration changes are atomic operations. This means that changes are made all at once or not at all, preventing partial upgrades. If an upgrade fails or the system becomes unstable, you can roll back to the previous configuration seamlessly.

Isolation of Environments

Nix allows for isolated user environments, which means each user on the system or each project can have its own set of packages, separate from the global system packages. This isolation helps prevent conflicts between different package versions required by different software.

Also read - File management in operating system

Nix: How It Works?

Nix is a powerful package manager that emphasizes reproducibility and declarative configuration. It operates based on a few key principles and mechanisms that ensure consistency and reliability in managing software packages and system configurations.

Key Principles and Mechanisms

  • Declarative Configuration: In Nix, the desired state of the system or environment is specified declaratively in configuration files. Users define what software and versions they need, along with their configurations, in .nix files. Nix then ensures that the system matches this specification.
  • Immutable Packages: Nix stores packages in a content-addressable store, typically located at /nix/store. Each package is identified by a unique hash derived from all inputs that went into building the package, including the source code, dependencies, and build instructions. This immutability ensures that once a package is built, it cannot be altered, guaranteeing consistency and preventing "dependency hell."
  • Isolation: Each package in Nix is built in isolation from others, ensuring that builds are reproducible and do not interfere with one another. This is achieved using isolated build environments, often through the use of lightweight virtual machines or sandboxing techniques.
  • Atomic Upgrades and Rollbacks: Nix allows for atomic upgrades and rollbacks of the entire system or individual packages. When a new package or configuration is installed, Nix creates a new generation in the /nix/store without modifying the existing state. Users can switch to new configurations or revert to previous ones seamlessly, without disrupting the system.
  • Garbage Collection: Nix includes garbage collection mechanisms to clean up old or unused packages and configurations. Since each package version is stored separately, users can safely remove outdated or unnecessary files without affecting the current system state.
  • Reproducible Builds: By capturing the exact dependencies and build instructions, Nix ensures that builds are reproducible. This means that the same .nix file will always produce the same output, regardless of the environment where it is built.

Practical Example

Consider a simple .nix file to install a specific version of nginx:

with import <nixpkgs> {};

stdenv.mkDerivation {
  name = "my-nginx";
  version = "1.20.1";
  src = fetchurl {
    url = "";
    sha256 = "0b1e4a6cbdfd0b2d3ad0e4c2db7b0d1b9f0190cd9383c9d6f1b10c5e1b473f4d";
  buildInputs = [ openssl pcre zlib ];

This file specifies the exact version of nginx to be installed, along with its source URL and dependencies. Nix uses this file to build and install nginx in an isolated and reproducible manner.

By adhering to these principles and mechanisms, Nix ensures that software management is reliable, consistent, and free from the typical issues associated with traditional package management systems.

Frequently Asked Questions

What is the main advantage of NixOS?

NixOS allows for reliable system configuration, atomic upgrades, rollbacks, and multiple versions of a package to coexist, leading to a predictable and manageable system.

Can I use Nix package manager without NixOS?

Yes, the Nix package manager can be installed and used on other Linux distributions and macOS.

How is package isolation achieved in NixOS?

NixOS achieves package isolation by storing each package in a unique directory path, preventing different versions from interfering with each other.


In conclusion, NixOS provides a novel approach to managing and configuring your operating system. By leveraging the power of the Nix package manager, it provides a level of reliability and predictability that's hard to match. With atomic upgrades and rollbacks, isolation of package environments, and declarative system configuration, NixOS offers a robust solution for those seeking a more manageable operating system.

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