Docker - Is volume mounted before running CMD

Question

I have docker compose like

volumes:
      - ./:/app

and dockerfile like

WORKDIR /app
CMD [ "npm", "run", "build"]

It working but i don't know somecase it don't work?. If volume mounted before CMD run, it will working but i don't know is that true?. I don't want copy file in docker file and if volume mounted before CMD run that sound good. Anybody know Is volume mounted before running CMD? (more: is that same with command in composer?) any document refer thanks.

Answer 1

Yes, volume is mounted before CMD is run.

This is covered in the OCI runtime spec with the "mount operations" before the runtime.