As of april 2024, the Debian 8 used as a base to the prefapp/debian-formacion is deprecated, and as such, the completion of the activity is no longer possible as stated.
A possible workaround could be editing the sources.list of the container, to have them updated to the deprecated images archive of Debian, but the exercise is doable simply using the latest version of Debian (debian:latest for example).
In the docker formation chapter, https://prefapp.github.io/formacion/cursos/docker/#/./02_docker/09_xestion_de_volumes the steps include using the prefapp/debian-formacion docker image, and to use it to install "curl".
As of april 2024, the Debian 8 used as a base to the prefapp/debian-formacion is deprecated, and as such, the completion of the activity is no longer possible as stated.
A possible workaround could be editing the sources.list of the container, to have them updated to the deprecated images archive of Debian, but the exercise is doable simply using the latest version of Debian (debian:latest for example).