Introduction to Docker

August 23, 2015 · docker, devops

Docker is a new open-source project that makes deployment of applications easier. The idea of this technology is very simple : “the application runs inside a software container. This container is acting like a mini Operating System”. Basics are very similar to Virtual machine : An OS is running independently of host’s OS. Networking is working using bridges… Docker is using 2 terms : image and container:

An image is a packaged application that is not running.
A container is an instance of image. It can be a running or stopped application.

In addition, Docker have a lot of advantages. let’s discover them!

Docker {: .center-image }

1. Docker Advantages

Lightweight comparing to normal Virtual machine. You can run many containers in parallel without having memory problems.
Docker can run on most operating systems. Containers running have no dependencies with host’s OS. So it simpifies developer’s tasks by exporting 1 application for all OS instead of 1 application for each specific operating System.
Deployment is easier using docker. Once your Docker image is built, your applications can be exported without any dependenncies. So that , you could gain a lot of time.
Docker have a large community. You can find the answers to all your questions and wonders on : StackOverflow, Github issues …
Docker have a public repository where you can find all applications that you want easily, how to configure it and how the image was built. Per example: you could fine Apache server image, or MySQL Server..
Docker is used today by very well know companies such as : Microsoft (that is a partner of Docker too), eBay, Baidu, Groupon… So that’s why you should have the curiousity about Docker and to give a try.
Scalability : docker offer the possibility to make your application scalable by running many instances1 of the same image.

2. How to Install Docker

For Ubuntu , run this command in your terminal :

curl -sSL https://get.docker.com/ | sh

For other OS , please refer to docker documentation

3. Verify Docker is installed correctly

Run this command in your terminal :

sudo docker run hello-world

4. Run docker as non-sudo user

Docker is used as root normally. But you can still use docker as non-root user. In order to do that, run this command in your terminal :

sudo usermod -aG docker $USER

5. But How to use Docker ?

In my next tutorial, we will manipulate docker containers. and I will show you how we connect a PhpMyAdmin to MySQL Server, both working on different docker containers on the same host.