CMD vs ENTRYPOINT

if we run simple ubuntu container on the docker, it will start ubuntu container then exit from it immediately.

• sudo docker run ubuntu
• sudo docker ps
• sudo docker ps -a

Examine nginx, mysql and ubuntu docker file and attend the CMD line

when we run the ubuntu image bash command couldnt find to anythink then it stopped the service immediately

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How do you specify a different command to start the container?

• once option is to append a command to the docker run command and that way it overrides the default command

• sudo docker run ubuntu [COMMAND]

• sudo docker run ubuntu sleep 5

• How do you make that change permenantly? We can create docker file and specify CMD

• Dockerfile:

FROM ubuntu
CMD sleep 5

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We can specify command with the JSON file format

• CMD ["command", "param1"]
• CMD ["sleep", "5"]

What if i wish to change the number of seconds it sleeps currently ? We can use append command like sudo docker run sleeper sleep 10 but in this way this commands doesnt look very good. We only want to pass in the number of seconds the container should sleep automatically like this sudo docker run ubuntu-sleeper 10. That is where entry point comes into play.

FROM ubuntu
ENTRYPOINT ["sleep"]

• default entry point parameter

FROM ubuntu
ENTRYPOINT ["sleep"]
CMD ["5"]  ---> defult entry point parameter