Guix and its package collection are updated by running guix pull.
By default guix pull downloads and deploys Guix itself from the
official GNU Guix repository. This can be customized by providing a
file specifying the set of channels to pull from (see Invoking guix pull). A channel specifies the 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.