Docker Guide

From Variscite Wiki
VAR-SOM-MX6 - Docker

1 Docker Introduction

Docker is a software platform that allows the creation, testing and distribution of applications via containers.
Containers let you run your applications in resource-isolated processes. There are some similarities to virtual machines, but containers are more portable, more resource-friendly, and enables faster software delivery cycles.
Often used with docker there's a companion tool known as docker-compose: compose is used for defining and running multi-container Docker applications.

You can check Docker online documentation at:
https://docs.docker.com/get-started/
https://docs.docker.com/compose/
https://training.play-with-docker.com/
https://docker-curriculum.com/

2 Yocto Integration

2.1 Recipe

Before you begin, get familiar with the Varicite Yocto Build Release guide.

Variscite provides a light reference image with Docker, var-image-docker.
This image is based on the core-image bbclass with the addition of a few more packages and features:

  • docker
  • python3-docker-compose
  • ssh-server-dropbear
  • basic command line tools

2.2 Create a Docker-ready Image

$ cd ~/var-fslc-yocto
$ MACHINE=var-som-mx6 DISTRO=fslc-x11 . setup-environment build_x11

Append the following to the conf/local.conf file in your Yocto build directory:

DISTRO_FEATURES_append = " virtualization"
$ bitbake var-image-docker

3 Test Docker

  • Check docker version:
root@var-som-mx6:~# docker --version

3.1 Test hello-world

  • Pull the hello-world image from Docker Hub:
root@var-som-mx6:~# docker pull hello-world
  • List docker images:
root@var-som-mx6:~# docker images
  • Run hello-world container:
root@var-som-mx6:~# docker run hello-world

Hello from Docker!
This message shows that your installation appears to be working correctly. To generate this message, Docker took the following steps:
1. The Docker client contacted the Docker daemon.
2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
3. The Docker daemon created a new container from that image which runs the
executable that produces the output you are currently reading.
4. The Docker daemon streamed that output to the Docker client, which sent it
to your terminal.

3.2 Test Ubuntu

  • Pull the ubuntu image from Docker Hub:
root@var-som-mx6:~# docker pull ubuntu
  • Run ubuntu:
root@var-som-mx6:~# docker run -it ubuntu
root@8637148015f5:/# apt update

root@8637148015f5:/# apt install nodejs

root@8637148015f5:/# node -v

root@8637148015f5:/# exit
root@var-som-mx6:~#

4 Test docker-compose

  • Check the docker-compose version:
root@var-som-mx6:~# docker-compose --version

4.1 Example: a RESTful-based data-logger

This archive provides an example of a RESTful-based data-logger to be deployed on an embedded device acting as an intelligent edge node in large connected networks.
Through a developed web service application based on the Tornado web framework, data can be easily inserted and retrieved from a MongoDB instance by remote devices.

In the tutorial the application is proposed as a Docker-based solution in which each component is run in a separate container.
Docker Compose is used to simplify the build of custom Docker images, their deployment, and configuration.
The application can be easily tested on any device which supports Docker and Docker Compose, be it a PC or an embedded device.