Docker in Docker. The real one

I also used to employ my own building pipeline to deliver docker images and I got to learn that my $5 Digital Ocean machine was getting stuck from time to time, because all of its available disk space was eaten up by generated docker images. The irony was that all of these artefacts were transient and needed for the purpose of building the main artefact only. That was the first time I though how cool it’d be, if I could generate intermediary artefacts and keep them entirely within builder container and, once it stopped, all that garbage gets removed. But that would require launching one docker container inside the other one...