Docker: ENTRYPOINT vs CMD

examples/curl-runner/Dockerfile

FROM ubuntu:23.04
RUN apt-get update
RUN apt-get install -y curl

ENTRYPOINT ["curl"]   # fixed part
CMD ["--silent", "https://httpbin.org/get"]  # replacable part

By default if you run a container based on this image, Docker will execute a command which is a combination of the ENTRYPOING + CMD.

However, on the command-line where you call docker run, you can provide a replacement for the CMD part.

Build the image:


$ docker build -t mydocker .

Running container this way will execute curl --silent https://httpbin.org/get


$ docker run --rm  mydocker

The user can replace the CMD part, so if we run this command, docker will execude curl https://szabgab.com/


$ docker run --rm  mydocker https://szabgab.com/

ENTRYPOINT
CMD