Docker cmd and entrypoint

 Docker - container only exist if the service alive

Example: ubuntu

If run docker run ubuntu and check docker ps -a, you find it stopped.

The reason is the CMD is only bash

To make it live create another dockerfile ubuntu-sleeper

FROM Ubuntu

CMD sleep 5

#docker build -t ubuntu-sleeper .

#docker run ubuntu-sleeper

If you want to change sleep time, you need to run

#docker run ubuntu-sleeper sleep 10

If want to remove sleep in command, you need to change to use ENTRYPOINT

FROM Ubuntu

ENTRYPOINT ["sleep"]

#docker build -t ubuntu-sleeper

#docker run ubuntu-sleeper 10

If you want to setup default value of sleep

FROM Ubuntu

ENTRYPOINT ["sleep"]

CMD ["5"]