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I just rebuilt, restarted, and its the same thing. Mysql container shows its dir, Apache container does not.
I may be on the wrong track here - I’ve only used Docker on Windows and Linux.
But a quick look indicates that on the Mac, using Kitematic or Docker Desktop for Mac, the containers are running in a Linux VM created behind the scenes. This seems similar to using WSL2 on Windows.
You may need to pay closer attention to how to map volumes back to the Mac file system.
In the Windows sort-of-equivalent (WSL2) the path to files on the Windows system as mapped to the Linux containers starts with /c/ instead of C:, for example.
Kitematic is part of Docker Toolbox, which was deprecated in favor of Docker Desktop for Mac/Windows.
Linux is the only plattform where docker is a first class citizen, everywhere else it is run on a virtualisation plattform in a linux vm.