Goals

Learn about the concept of containers and their applications in development and deployment of software. Use Docker to create and launch containers.

Examples

• Build and run docker containers

Exercises

• Build and publish a container image with a static website server
• Build a Docker compose stack with a counter application

Introduction

What are containers?

Containers and Virtual Machines

Containers are an abstraction at the app layer. A container engine allows to run multiple containers on the same machine. Each container shares the OS kernel with other containers. A container is "just a process".

Virtual Machines are an abstraction of physical hardware. A hypervisor allows to run multiple VMs on a single machine. Each VM includes a full copy of an operating system.

Docker: What is a container?

Example

To start a container we can use the run command. It’s easy to spawn multiple containers and they start instantly:

docker run -ti alpine

Resource Isolation

A major feature of containers is their resource isolation. When you start a container, the container has its own:

To enable containers to cooperate, files, networks and processes can explicitly be shared.

Example

Again, we start a new container:

docker run -ti alpine