 will run with the OS exec: no shell that could interfere with signal handling
- A container starts with a single command, and when that command exits,
  the container exits. So if you define both, docker turns that into one command.
- If you use ENTRYPOINT and CMD together, you want the Json syntax

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# Dockerfile Variables

- `ARG` sets a variable within the Dockerfile, scoped
  - Value overridden with flags on the build command
- `ENV` sets a variable inside the container (image metadata)
- Variables 