Practically, what is the difference between docker run -dit(-itd) vs docker run -d?

Question

I've used docker run -it to launch containers interactively and docker run -d to start them in background. These two options seemed exclusive. However, now I've noticed that docker run -dit (or docker run -itd) is quite common. So what is the difference? When -it is really needed together with -d?

Answer 1

Yes, sometimes, it's necessary to include -it even you -d

1. When the ENTRYPOINT is bash or sh

   docker run -d ubuntu:14.04 will immediately stop, cause bash can't find any pseudo terminal to be allocated. You have to specify -it so that bash or sh can be allocated to a pseudo terminal.

    docker run -dit ubuntu:14.04
   

2. If you want to use nano or vim with any container in the future, you have to specify -it when the image starts. Otherwise you'll get error. For example,

    docker run --name mongodb -d mongo
    docker exec -it mongodb bash
    apt-get update
    apt-get install nano
    nano somefile
   

   It will throw an error

   Error opening terminal: unknown.