Docker and docker compose

When you hear people talking about Docker and/or Docker Compose, it sounds exciting but it sounds a bit like gibberish because everything is too technical.
The learning curve is not exactly smooth, although thanks to Youtubers like “Pelado Nerd” you can save yourself a lot of headaches.

I love Docker, and the more I know about this type of virtualization so close to the operating system (which has nothing to do with virtualizing machines with VirtualBox and similar), the more things I virtualize.

You can virtualize development environments, cms’s, online stores.
With Docker you can even virtualize applications (at least in Linux), you can find on the web wide world for example, how to virtualize the famous sublime text with docker compose.

And what is Docker?

Docker Images and Containers

When you do a docker build or docker up, the first thing Docker will do is build the images, and then the containers.

If your docker-compose file contains the ingredients for Apache, Nginx, WordPress, and Phpmyadmin, this will automatically build each of those images.

It will then create a container for each of those images.

The container is an instance of the image. As if the image were a template and the container an extension of it.

And if we clone this environment, or create another one that also uses Apache, it will use that same image.

That is, if we have 5 virtualized sites with Docker that use Apache, it will not install 5 Apaches, but it will install only 1 and it will be shared for all containers.

More about Docker

The magic of docker is such that you can run php 5 environments while your machine remains on version 7.2, or simply does not have php.

The way everything works in docker is by forming a network between containers, where they see and understand each other through ports.

For example, you install a mysql specifying port 8090.
You install 3 different cms’s, which are going to need mysql. So you tell them that their mysql is on port 8090. And that's it…

You install a software with a php 4, uuuuuuuuuuuuuuuuuu, for port 9091.
In the browser you will use localhost:9091 and it will look like the software is on your own machine.
You can also enter the container, and work inside and run things in it, which would be the analogue of being in the console of a virtualbox.

And what is docker compose?

Well, if Docker is magic, docker compose is beyond words.
Docker compose is a little file, where you describe the list of images and containers you want to create, and how they interconnect with each other.

It's like a cooking recipe, where you declare what ingredients you use and how you mix them.

This is done with the docker-compose.yml command
And when you are in the folder of said file, you do «docker-compose up».
Then the thermo-mix acts 😀

Example of a wordpress docker-compose:

services: 
  php: 
    image: wordpress 
    restart: 'always' 
    ports: 
      - 0.0.0.0:80:80 
    depends_on: 
      - mysql 
    links:  
      - mysql 
    volumes:  
      - ./data/www:/var/www/html 
 
  mysql: 
    image: mysql 
    restart: 'always' 
    volumes:  
      - ./data/mysql:/var/lib/mysql 
    environment: 
      MYSQL_ROOT_PASSWORD: root 
      MYSQL_DATABASE: my_site 
      MYSQL_USER: root 
      MYSQL_PASSWORD: root

p>Where «volumes» These are volatile data.
Look at mysql, volumes. We are making the mysql data available. in a folder shared with the host. ('host' is our real machine, 'container' is the inside of docker)

So, when we zip the folder where the docker-compose.yml file is located, and take it somewhere else, the new container will 'hook' the mysql data again.

Advantages of dockerizing an environment.

• You can “turn on” or “turn off” those cms’s and robots with a single console command “docker-compose up” and “docker-compose down” (and with it the resources taken up by all those components that you won't need if you turn on your PC to listen to music)
• You can decide which data is volatile (mysql, plugins, images) and place them in a folder on the host
• When you copy and clone a Docker-compose folder and its volatile data, when you recreate the container somewhere else you won't need to configure anything (that's one of the great things about Docker)
• Before doing a risky operation, as I mentioned in the previous point, you copy the entire folder, and voila. You don't have to go through the arduous task of having to export and import databases (if you set it up right, of course)
• You can grab the wordpress from the server, download it to your local, and everything is set up with a «docker-compose up». You'll only need to change the url configuration, and you'll have an identical copy on your local in a few minutes and with almost no effort.
• When a client tells me that something is not working well in their prestashop, and I find it difficult to analyze it on their server, there will be a huge difference between whether their environment is in a Docker or not.
  If it is, bingo! I just have to download it, start it on my local machine, and analyze and debug everything locally.
• You can have your desktop PC, with your personal stuff, your games, multimedia tools, without installing the work environments that you don't like to have on your real machine, which can often cause problems.
  Personally, I don't like having an Apache or an Nginx in my real environment, and having to update or maintain it. Or that when it breaks, it forces you to rack your brains or reinstall the entire operating system because of this.
  Or vice versa, that your system breaks, and when you reinstall it you have to start from scratch, and reinstall Apache, MySQL, Postgres, import all the databases.
  If I have it in Docker, I just have to install Docker, do "docker-compose up" in every place, and it's like the difference between making a cup of coffee and having to paint the house again.

If you've never tried docker-compose, when you do it will be like eating sunflower seeds, you won't want to stop learning and using it more and more.