nixosrebuild

nixosrebuild is a command-line tool used to manage the configuration of NixOS. NixOS is a Linux distribution built on the Nix package manager, which allows for declarative system configuration. NixOS uses a declarative approach, meaning that the desired state of the system is described in configuration files, and nixosrebuild is the tool responsible for applying these descriptions to build and activate new system generations.

When a user modifies their NixOS configuration files, typically located in /etc/nixos/, they run nixosrebuild. This command takes the configuration files as input and uses the Nix package manager to build a new system generation. This build process includes installing all necessary packages, setting up system services, and configuring the operating system according to the declared state. Once the build is complete, nixosrebuild can be instructed to switch to this new generation, making it the active system.

A key feature of nixosrebuild is its atomic upgrades and rollbacks. If a new configuration fails to build or results in an undesirable state, the previous generation remains unaffected and can be easily reverted to. This ensures system stability and provides a safety net for system administration. The tool also manages bootloader entries, allowing users to select which system generation to boot into from the boot menu. Furthermore, nixosrebuild can be used to test configurations without immediately activating them, enabling a safer development workflow.