nix-flake
Build and manage Nix projects using flakes
TLDR
Create a new flake (just the flake.nix file) from the default template, in the current directory
Update all inputs (dependencies) of the flake in the current directory
Update a specific input (dependency) of the flake in the current directory
Show all the outputs of a flake on github
Display help
SYNOPSIS
nix flake
PARAMETERS
archive
Create an archive of the flake.
check
Check the flake for errors.
clone
Clone a flake from a URL.
init
Initialize a new flake in the current directory.
lock
Generate or update the flake's lock file.
metadata
Show the metadata of a flake.
new
Create a new flake from a template.
output
Show the outputs of a flake.
show
Show the flake's definition.
update
Update the flake's dependencies.
DESCRIPTION
nix flake is a powerful feature of the Nix package manager that provides a declarative, reproducible, and composable way to manage system configurations, development environments, and software packages.
Flakes define inputs (dependencies) and outputs (packages, applications, development shells) in a `flake.nix` file. This file acts as a central definition for your project's build process and dependencies, ensuring consistency across different machines and over time.
Using flakes, you can precisely specify versions of dependencies, eliminating dependency conflicts. Flakes also enable isolated development environments, meaning changes made in one project won't affect other projects.
Flakes improve the reproducibility of builds by explicitly declaring dependencies and providing a mechanism for version pinning. They simplify the sharing and collaboration of projects by providing a standardized way to define and build projects.
CAVEATS
Flakes are still considered an experimental feature in Nix. Their syntax and behavior may change in future versions. Requires Nix version 2.0 or higher and `experimental-features = nix-command flakes` enabled in the nix.conf file.
EXAMPLE: BASIC FLAKE.NIX
A basic `flake.nix` file might define a single package:
{
inputs = { nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable"; };
outputs = { self, nixpkgs }: {
defaultPackage.x86_64-linux = nixpkgs.pkgs.hello;
};
}
This example fetches `nixpkgs` and defines a package named `hello`.
ACTIVATING FLAKES
To use flakes, the following line must be enabled in `/etc/nix/nix.conf`:
`experimental-features = nix-command flakes`
Then restart the nix daemon: `sudo systemctl restart nix-daemon`
HISTORY
Flakes were introduced as an experimental feature in Nix to address challenges with reproducibility and dependency management in traditional Nix workflows. They provide a more declarative and structured approach to defining Nix projects. The initial design and implementation were aimed at simplifying project setup, improving consistency, and enabling better collaboration. Since introduction, flakes have been improved over time by Nix community.
