The docs at https://wikitech.wikimedia.org/wiki/Portal:Data_Services/Admin/Quarry describe the 'bare metal' cluster from before @rook's work to deploy and manage the service within a Magnum Kubernetes cluster. There is lore that has been passed back and forth via IRC about how to access and manage parts of the new system. This lore needs to make it to the wiki.
https://github.com/toolforge/quarry/blob/main/README.md will be helpful as well.