FROM ubuntu:trusty CMD ["/bin/ping","localhost"]
$ docker run -d demo 15bfcddb11b5cde0e230246f45ba6eeb1e6f56edb38a91626ab9c478408cb615 $ docker ps -l CONTAINER ID IMAGE COMMAND CREATED 15bfcddb4312 demo:latest "/bin/sh -c 'ping localhost'" 2 seconds ago
RUN apt-get install python3 CMD echo "Hello world" ENTRYPOINT echo "Hello world"