lesson-2

Spin up a container

Let's run your first container using a simple command:

$ docker container run <image name>

<image name> specifies what image to use to spin up an instance of a container.

An image contains the application to run inside a container.

Let's spin up a container that uses hello-world:latest image:

$ docker container run hello-world:latest

You might notice latest in the image name and wonder what's that. It's called an image tag, which is used to specify a particular version of an image.

If the tag is not specified with the image name, the latest tag is assumed. So if you run the following, the same image will be used:

$ docker container run hello-world

Yay, you just ran your first container!

So, what happened exactly?

So let's see what happened when you ran the following command:

$ docker container run hello-world:latest

The end result of the above command was tu run a container, but internally, it did the following:

• docker command sends the above request to the Docker Daemon, which is running in the background.
• The daemon upon receiving the command, check if the image exists.
• The daemon downloads/pulls the hello-world:latest image from a default registry called Docker Hub.
• The daemon created a container with the specified image.
• The daemon streamed the output to the docker command which is then displayed on your terminal.

List the containers

But let's check:

$ docker container ls

Hmm, nothing showed up?

That's because the hello-world:latest image contains an application which prints out some text and closes immediately. docker container ls only shows currently running containers.

Let's check it again:

$ docker container ls --all

This will show all the containers.

Did you find the one you just created? You'll see a container with EXITED status, that's the one.

Remove a container

Let's remove the container so it looks clean again:

$ docker container rm <container id>

You can get the <container id> from docker container ls --all command.

Protip

Docker developers are nice people. They know you'll be using some commands very frequently, so they created some short commands:

Long command	Short command
docker container run <image name>	docker run <image name>
docker container ls	docker ps
docker container rm <container id>	docker rm <container id>

From now on, we will be using the shorter version of the commands.

The next lesson talks about registry and some operations related to images.