Criando um canal (Manual de referência do GNU Guix)

6.7 Criando um canal

Let’s say you have a bunch of custom package variants or personal packages that you think would make little sense to contribute to the Guix project, but would like to have these packages transparently available to you at the command line. By creating a channel, you can use and publish such a package collection. This involves the following steps:

A channel lives in a Git repository so the first step, when creating a channel, is to create its repository:
```
mkdir my-channel
cd my-channel
git init
```
The next step is to create files containing package modules (veja Módulos de pacote), each of which will contain one or more package definitions (veja Definindo pacotes). A channel can provide things other than packages, such as build systems or services; we’re using packages as it’s the most common use case.
For example, Alice might want to provide a module called (alice packages greetings) that will provide her favorite “hello world” implementations. To do that Alice will create a directory corresponding to that module name.
```
mkdir -p alice/packages
$EDITOR alice/packages/greetings.scm
git add alice/packages/greetings.scm
```
You can name your package modules however you like; the main constraint to keep in mind is to avoid name clashes with other package collections, which is why our hypothetical Alice wisely chose the (alice packages …) name space.

Note that you can also place modules in a sub-directory of the repository; veja Módulos de pacote em um subdiretório, for more info on that.
With this first module in place, the next step is to test the packages it provides. This can be done with guix build, which needs to be told to look for modules in the Git checkout. For example, assuming (alice packages greetings) provides a package called hi-from-alice, Alice will run this command from the Git checkout:
```
guix build -L. hi-from-alice
```
... where -L. adds the current directory to Guile’s load path (veja Load Paths em GNU Guile Reference Manual).
It might take Alice a few iterations to obtain satisfying package definitions. Eventually Alice will commit this file:
```
git commit
```
As a channel author, consider bundling authentication material with your channel so that users can authenticate it. Veja Autenticação de canal, and Especificando autorizações de canal, for info on how to do it.
To use Alice’s channel, anyone can now add it to their channel file (veja Especificando canais adicionais) and run guix pull (veja Invocando guix pull):
```
$EDITOR ~/.config/guix/channels.scm
guix pull
```
Guix will now behave as if the root directory of that channel’s Git repository had been permanently added to the Guile load path. In this example, (alice packages greetings) will automatically be found by the guix command.

Voilà!

Aviso: Before you publish your channel, we would like to share a few words of caution:

Before publishing a channel, please consider contributing your package definitions to Guix proper (veja Contribuindo). Guix as a project is open to free software of all sorts, and packages in Guix proper are readily available to all Guix users and benefit from the project’s quality assurance process.
Package modules and package definitions are Scheme code that uses various programming interfaces (APIs). We, Guix developers, never change APIs gratuitously, but we do not commit to freezing APIs either. When you maintain package definitions outside Guix, we consider that the compatibility burden is on you.
Corollary: if you’re using an external channel and that channel breaks, please report the issue to the channel authors, not to the Guix project.

You’ve been warned! Having said this, we believe external channels are a practical way to exert your freedom to augment Guix’ package collection and to share your improvements, which are basic tenets of free software. Please email us at guix-devel@gnu.org if you’d like to discuss this.