7.3 Replicación de Guix

The guix describe command shows precisely which commits were used to build the instance of Guix we’re using (see Invocación de guix describe). We can replicate this instance on another machine or at a different point in time by providing a channel specification “pinned” to these commits that looks like this:

;; Despliega unas revisiones específicas de mis canales de interés.
(list (channel
       (name 'guix)
       (url "https://git.savannah.gnu.org/git/guix.git")
       (commit "d894ab8e9bfabcefa6c49d9ba2e834dd5a73a300"))
      (channel
       (name 'paquetes-personalizados)
       (url "https://example.org/paquetes-personalizados.git")
       (branch "dd3df5e2c8818760a8fc0bd699e55d3b69fef2bb")))

To obtain this pinned channel specification, the easiest way is to run guix describe and to save its output in the channels format in a file, like so:

guix describe -f channels > channels.scm

The resulting channels.scm file can be passed to the -C option of guix pull (see Invocación de guix pull) or guix time-machine (see Invocación de guix time-machine), as in this example:

guix time-machine -C channels.scm -- shell python -- python3

Given the channels.scm file, the command above will always fetch the exact same Guix instance, then use that instance to run the exact same Python (see Invoking guix shell). On any machine, at any time, it ends up running the exact same binaries, bit for bit.

Pinned channels address a problem similar to “lock files” as implemented by some deployment tools—they let you pin and reproduce a set of packages. In the case of Guix though, you are effectively pinning the entire package set as defined at the given channel commits; in fact, you are pinning all of Guix, including its core modules and command-line tools. You’re also getting strong guarantees that you are, indeed, obtaining the exact same software.

Esto le proporciona superpoderes, lo que le permite seguir la pista de la procedencia de los artefactos binarios con un grano muy fino, y reproducir entornos de software a su voluntad—un tipo de capacidad de “meta-reproducibilidad”, si lo desea. See Inferiores, para otro modo de tomar ventaja de estos superpoderes.