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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?

techkuz
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vehsakul
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    `-i` starts an interactive session and `-t` emulates a tty. But `-d` tells Docker to detach and run in the background. They don't really make sense together... – Dan Lowe Jan 29 '17 at 00:47
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    @DanLowe That's why I asked. It is used on [docker site](https://docs.docker.com/engine/reference/commandline/container_update/) and elsewhere. – vehsakul Jan 29 '17 at 00:50
  • Yeah you do have a point. I thought maybe it would change behavior of `docker attach` ... but I don't see any difference. Good question. – Dan Lowe Jan 29 '17 at 01:00

1 Answers1

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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.

Rafaf Tahsin
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