Efraim Flashner <efraim@flashner.co.il> writes:

> * gnu/packages/debian.scm (ubuntu-keyring): New variable.

[...]

> +    (build-system trivial-build-system)
> +    (arguments
> +     `(#:modules ((guix build utils))
> +       #:builder (begin
> +                   (use-modules (guix build utils))
> +                   (let* ((out (assoc-ref %outputs "out"))
> +                          (apt (string-append out "/etc/apt/trusted.gpg.d/"))
> +                          (key (string-append out "/share/keyrings/")))
> +                     (setenv "PATH" (string-append
> +                                      (assoc-ref %build-inputs "gzip") "/bin:"
> +                                      (assoc-ref %build-inputs "tar") "/bin"))
> +                     (invoke "tar" "xvf" (assoc-ref %build-inputs "source"))
> +                     (for-each (lambda (file)
> +                                 (install-file file key)
> +                                 (install-file file apt))
> +                               (find-files "." "\\.gpg$")))
> +                   #t)))

Why is having the same files in out/share/keyrings and
out/etc/apt/trusted.gpg.d necessary?

(this was perhaps the case with the Debian keyring too?)