This article provides an introduction to Docker for a non-technical audience.

Why would non-technical people care about docker?

Within my organisation, like many others, we have mixed technical and non technical team members. Within the tech team, we are often using jargon and tech terms. I think it is important to educate and make sure, all staff, no matter tech background, can understand to a basic level, what we are talking about.

Docker as DevEnv

Docker is actually a large and quite complex application and eco system. There are many advanced features. For this particular article, I want to narrow down the focus to a particular use case of docker, which is to help us setup our computers and laptops ready for application testing and development. This particular use case is often referred to as a development environment (DevEnv).

What do I mean by that?

Essentially, what I can going to talk about is how we can use docker to create a virtual machine on your laptop that acts like a server. Docker can help us achieve this in a consistent and efficient manner.

This is a simplified scenario, but typically, if we want to develop an application, we need a server, with two main components, the web service part, and the database part.

Docker DevEnv Components

I am going to use a php laravel example that you can read more about if interested. In this explanation, I am going to concentrate on two main components:

Web service part is so we can www.application.com and get a result.
Database part is so we can store/retrieve information.

I am going to explain with these components using two files. There is a lot more happening here, but for simplicity, I am just going to concentrate on two files. A Dockerfile and a docker-compose.yml file. These are both in yaml format, so are easily readable.

Dockerfile sample

docker-compose.yml sample

Dockerfile

As you can see from the Dockerfile, this describes the basic server setup. This is the virtual server that will be setup on your laptop when starting docker with these files.

Three main parts I want to draw your attention to. Lines 1 and 2.

#Ubuntu 18.04 Base Image - Nginx + MySQL + PHP 7.2 [LEMP]
FROM ubuntu:18.04
...

This described the type of server operating system. This could be CentOS etc, but in this case, it is Ubuntu.

Lines 42 to 50 show certain php libraries being installed. In this case, they are installed as per the latest version for this operating system, Ubuntu 20.04. But, depending on OS, we can specific the version. This would be something we are going to look at in order to replicate our production servers and closely as possible.

...
php-fpm \
php-cli \
php-common \
php-zip \
php-mbstring \
php-bcmath \
php-image-text \
php-gd \
php-mysql \
...

Lines 53 to 55 show the installation of database, in this case, mysql.

...
mysql-server \
mysql-client \
mysql-common \
...

Here is a look at the entire dockerfile in this example.

#Ubuntu 18.04 Base Image - Nginx + MySQL + PHP 7.2 [LEMP]
FROM ubuntu:18.04

#Label
LABEL version="1.0"
LABEL name="ubuntu-base+nginx+mysql+php"

#Set TZ
ENV TZ=Europe/London
RUN ln -snf /usr/share/zoneinfo/$TZ /etc/localtime && echo $TZ > /etc/timezone

#apt update & install
RUN apt-get update && apt-get install -y \
        git \
        curl \
        libpng-dev \
        libonig-dev \
        libxml2-dev \
        libzip-dev \
        zip \
        unzip \
        graphviz \
        npm \
        libxpm4 \
        libxrender1 \
        libgtk2.0-0 \
        libnss3 \
        libgconf-2-4 \
        chromium-browser \
        xvfb \
        gtk2-engines-pixbuf \
        xfonts-cyrillic \
        xfonts-100dpi \
        xfonts-75dpi \
        xfonts-base \
        xfonts-scalable \
        imagemagick x11-apps \
        libwebp-dev \
        libfreetype6-dev \
        libjpeg62-dev \
        libpng-dev libxpm-dev \
        php-fpm \
        php-cli \
        php-common \
        php-zip \
        php-mbstring \
        php-bcmath \
        php-image-text \
        php-gd \
        php-mysql \
        composer \
        nginx \
        mysql-server \
        mysql-client \
        mysql-common \
        php-xml \
        php-curl

docker-compose

A few keys points from the docker-compose file. If you look at the first block, this is essentially starting up the server, using the image as you have just see in previous section dockerfile (it is actually a bit more complicated than that, but, for simplicity).

...
  # LEMP Server from image
  app:
    image: lemp-dev:v2
    container_name: webapp
    env_file:
      - .env
    working_dir: /var/www/html/
    ports:
        - 80:80    
        - 443:443
        - 3306:3306        
    volumes:
      - ../www:/var/www/html/
    networks:
      - lempnet
    tty: true
...

There are some settings that you don’t have to understand for the purposes of our use case in the section.

The second part is starting phpmyadmin from the official image on the docker hub web repository.

...
  # DB access via PHP my admin
  phpmyadmin:
    image: phpmyadmin
    container_name: phpmyadmin
    environment:
      - PMA_ARBITRARY=1
    restart: always
    ports:
    - 8181:80
    networks:
      - lempnet
...

Here is a look at the complete docker-compose file

version: "3.3"

networks:
  # docker internal network
  lempnet:
    driver: bridge

services:

  # LEMP Server from image
  app:
    image: lemp-dev:v2
    container_name: webapp
    env_file:
      - .env
    working_dir: /var/www/html/
    ports:
        - 80:80    
        - 443:443
        - 3306:3306        
    volumes:
      - ../www:/var/www/html/
    networks:
      - lempnet
    tty: true
 
  # DB access via PHP my admin
  phpmyadmin:
    image: phpmyadmin
    container_name: phpmyadmin
    environment:
      - PMA_ARBITRARY=1
    restart: always
    ports:
    - 8181:80
    networks:
      - lempnet

Docker desktop

Here is a look what the docker desktop application looks like on MacOS.

You can read more about how I have used docker in my other projects.