Start Multiple Docker Containers

In this lecture we’re running two containers side-by-side.

Video

This shows the difference between containers and images. We will create two containers (linux1, linux2) based on the same image (ubuntu)


docker run -it -d --rm --name linux1 ubuntu /bin/bash

This command:

creates container named “linux1”
additional flags:
- -d starts the container as “detached”. Use “docker attach” to attach to it later on.
- --rm cleans up the container after stopping. The container will be removed, basically the same as “docker rm container_identifier” after stopping the container. So everything is kept tidy.
- --name will give the container a dedicated name, which makes it easier to address the container later on.

Next we’ll start the second container:


docker run -it -d --rm --name linux2 ubuntu /bin/bash

👆🏻 This creates container “linux2”


docker attach linux1

This 👆🏻 attaches to container linux1

ls

This lists the file system on linux1


mkdir mylinux1

Creates a new directory on container linux1

ls

Shows that “mylinux1” was created


docker attach linux2

Attaches to container linux2

ls

This one does a few things:

Shows that the directory of linux2 is different than linux1, although they are both from the same image “ubuntu”
They are separated, they don’t share their file-system
The bash process is isolated in the container


exit

This will exit the bash and also remove the container because of the —rm command


docker ps -a

Shows only one container which is running, the other one got removed


exit

Exits the only running container linux1 and deletes the container

On any CLI enter


docker ps -a

That should show you nothing anymore. Perfect, cleanup is done, let’s continue!