@syncer I could try. I'm just not sure what the motivation/use-case would be? I can think only of very specific cases where someone would want to do mirror thus I'm not sure if it justifies the existence in the docs. Someone may want to have local mirror if they do a lot of reruns of the image build process but that's seems like very much edge-case.

If you can use the APT then you can create mirror as well - the same way APT talks to the repository. There is no need for additional protocols like rsync.