Difficulty: beginner
Estimated Time: 3 minutes

Docker is a computer program that performs operating-system-level virtualization, also known as "containerization". It was first released in 2013 and is developed by Docker, Inc.

In this course you will get familiar with Docker terminology. Starting of by understanding the high-level Architecture.

Docker Architecture

Containers

Docker is used to run software packages called "containers". Containers are isolated from each other and bundle their own application, tools, libraries and configuration files; they can communicate with each other through well-defined channels. All containers are run by a single operating system kernel and are thus more lightweight than virtual machines.

Images

Containers are created from "images" that specify their precise contents.

Registry

Images are often created by combining and modifying standard images downloaded from public repositories or so called docker registries.

Client

In this course you will use a terminal session as client to run docker commands using the Docker Daemon. One of the big advantages of using Katacoda is that it provides environments where Docker is installed for us. Thus no installations are necessary prior to this course. Just start right away by using a terminal session online!

You've completed your first IOVIO Docker Scenario!

What is Docker?

Step 1 of 3

What is a container?

A container is a runtime instance of a docker image.

A Docker container consists of

  • A Docker image
  • An execution environment
  • A standard set of instructions

The concept is borrowed from Shipping Containers, which define a standard to ship goods globally. Docker defines a standard to ship software.

Check docker version

docker version

List docker features

docker

Search for the hello-world image on docker hub

docker search hello-world

Download this image from docker hub

docker pull hello-world

List the downloaded image

docker images

Create and run a container based on the hello-world image

docker run --name name-of-container hello-world

The hello-world image is build to only print information. Once finished the container stops. Later in this course we will run containers that remain active.

List the exited container

docker ps -a

Check what the argument -a does

docker ps --help

Delete the container

docker rm name-of-container

Delete the image

docker rmi hello-world