DNS caching files not configured

I just installed bind9 on a Debian system and I am trying to understand how it works and what it does.

What is puzzling me is that no cache file is created in the cache. Well, actually, at one level, I perfectly understand. In all configuration files, the file directive names the file starting with "/ etc / bind", that is, the configuration file. There is a root hint file and files for the loopback system. No file is configured without a leading "/" so I'm not surprised. It is also not defined as subordinate to any domain.

So, if I understand correctly, it caches all of its searches in memory, but not in a file as I expected.

Now what I would like to do is make the nameserver more authoritative for my local private network and loopback system, but the filesystem cache is all the other answers. I can see how to do the first, but I cannot see where I would put the file directive so that it would cache all of its iterative responses.

I see that I can make it a slave to the well-known authoritative servers of all top-level domains I can think of, but that seems wrong and fragile in many ways.