84 lines
3.6 KiB
Markdown
84 lines
3.6 KiB
Markdown
# Nixpkgs
|
|
|
|
`Nixpkgs` is the massive collection of Nix expressions that define essentially *all* software available for Nix. It's the standard library for Nix, containing tens of thousands of packages. When you interact with `nixpkgs` in your Nix expressions, you're using this vast resource.
|
|
|
|
## How to Get Packages from Nixpkgs
|
|
|
|
The simplest way to use a package from Nixpkgs is to import it:
|
|
|
|
```bash
|
|
nix eval --impure --expr 'with import <nixpkgs> {}; pkgs.hello'
|
|
```
|
|
|
|
This evaluates an expression that imports Nixpkgs and makes its contents available as `pkgs`. The result will be a Nix store path for the `hello` package derivation.
|
|
|
|
You can also use `nix build`:
|
|
|
|
```bash
|
|
nix build nixpkgs#hello
|
|
```
|
|
|
|
This will build and symlink `hello` into your current directory as `result`.
|
|
|
|
And `nix run`:
|
|
|
|
```bash
|
|
nix run nixpkgs#hello/bin/hello
|
|
```
|
|
```
|
|
Hello, world!
|
|
```
|
|
|
|
> You could also run `./result/bin/hello`.
|
|
|
|
This command tells Nix to run the `hello` executable from the `hello` package in Nixpkgs.
|
|
|
|
## Searching Nixpkgs
|
|
|
|
You can search for packages directly from your terminal:
|
|
|
|
```bash
|
|
nix search nixpkgs firefox
|
|
```
|
|
|
|
This command will list all packages in your Nixpkgs channel that contain "firefox" in their name or description. You'll likely see results like `firefox` and `firefox-bin`.
|
|
|
|
However, the CLI is slow and not convenient to use. You should use the [Nixpkgs search](https://search.nixos.org/packages?channel=unstable) instead.
|
|
|
|
This is the entry of Firefox in Nixpkgs:
|
|
|
|
|
|
|
|
### How to install *firefox*?
|
|
|
|
You can use Nix as a traditional package manager:
|
|
|
|
```bash
|
|
nix-env -iA nixpkgs.firefox
|
|
```
|
|
|
|
This is **not recommended** as packages installed this way must be updated and maintained by the user in the same way as with a traditional package manager. To temporarily install a package for testing purposes, use `nix-shell` instead:
|
|
|
|
```bash
|
|
nix-shell -p firefox
|
|
```
|
|
|
|
This will spawn a shell with `firefox` available. To permanently install a package with Nix, add it to your NixOS or Home Manager configuration. NixOS and Home Manager will be covered later in this guide.
|
|
|
|
## `pkgs.lib` utility functions
|
|
|
|
The `pkgs` argument (or `nixpkgs` itself) isn't just a list of applications; it also provides a powerful utility library called `pkgs.lib`. This library contains helper functions for working with Nix expressions, strings, lists, and more.
|
|
|
|
Many of these functions are used extensively within Nixpkgs itself to define packages and modules. You can browse the full [`pkgs.lib` documentation online](https://nixos.org/manual/nixpkgs/stable/#sec-functions-library) for more details.
|
|
|
|
## The Nixpkgs GitHub Repository
|
|
|
|
Nixpkgs is an open-source project hosted on GitHub: [github.com/NixOS/nixpkgs](https://github.com/NixOS/nixpkgs). You can explore its source code to see how packages are defined. Every package definition is a Nix expression!
|
|
|
|
For example, you could find the definition for `hello` at `pkgs/by-name/he/hello/package.nix`. It uses `stdenv.mkDerivation` just like our example.
|
|
|
|
## Binary Caches
|
|
|
|
Building everything from source every time can be slow. Nix solves this with **binary caches**. When someone builds a derivation, if that exact derivation (with its exact hash) has already been built and uploaded to a binary cache (like [`cache.nixos.org`](https://cache.nixos.org/)), Nix will simply *download* the pre-built binaries from the cache instead of building it locally.
|
|
|
|
This is possible because of the unique hashing of store paths. If the hash matches, the content *must* be identical, so a downloaded binary is guaranteed to be the same as one built locally. This significantly speeds up package installation and system updates.
|