Guix and its package collection are updated by running guix pull
(see Invoking guix pull). By default guix pull downloads and
deploys Guix itself from the official GNU Guix repository. This can be
customized by defining channels in the
~/.config/guix/channels.scm file. A channel specifies a URL and
branch of a Git repository to be deployed, and guix pull can be
instructed to pull from one or more channels. In other words, channels can
be used to customize and to extend Guix, as we will see
below. Guix is able to take into account security concerns and deal with
authenticated updates.