Thanks!
Knowing about the --cidfile arg is helpful.
And knowing that “If you don’t change the hostname, then the default hostname is the short version of the container id.” is very helpful.
Sometimes I have a tiny lag between when a file is written to a mounted directory inside/outside the container and when I can read it from the other side. I worry that (some of the time) my program inside the container would look for the file before it could see it, because of this delay.