A Beginner’s Guide to Docker

This is a beginner’s guide to Docker which is a way to isolate and run entire applications. With Docker it doesn’t matter if you are using a Mac, Windows, or Linux computer anymore. The entire development environment is isolated: programming language, software packages, databases, and more.

Linux Containers

Docker is really just Linux containers which are a type of virtualization.Virtualization has its roots at the beginning of computer science when large, expensive mainframe computers were the norm. How could multiple programmers use the same single machine? The answer was virtualization and specifically virtual machines which are complete copies of a computer system from the operating system on up.

let’s create our own image for something more “real.” on django

$ cd ..
$ mkdir djangoapp && cd djangoapp
$ poetry install django==3.0
$ poetry shell```

(djangoapp) $ django-admin startproject example_project .

(djangoapp) $ python manage.py runserver

Dockerized Django

$ touch Dockerfile
$ touch docker-compose.yml

# Dockerfile

# Python version
FROM python:3.7-alpine

# Set environment variables
ENV PYTHONDONTWRITEBYTECODE 1
ENV PYTHONUNBUFFERED 1

# Set work directory
WORKDIR /code

# Install dependencies
COPY Pipfile Pipfile.lock /code/
RUN pip install pipenv && pipenv install --system

# Copy project
COPY . /code/

# docker-compose.yml
version: '3.7'

services:
  web:
    build: .
    command: python /code/manage.py runserver 0.0.0.0:8000
    volumes:
      - .:/code
    ports:
      - 8000:8000

$ docker-compose up --build
Creating network "djangoapp_default" with the default driver
Building webStep 1/6 : FROM python:3.7-alpine
...
Successfully built 047a6d848c5b
Successfully tagged djangoapp_web:latest
Recreating djangoapp_web_1 ... done
Attaching to djangoapp_web_1
web_1  | Performing system checks...
web_1  |
web_1  | Watching for file changes with StatReloader
web_1  | System check identified no issues (0 silenced).
web_1  |
web_1  | You have 17 unapplied migration(s). Your project may not work properly until you apply the migrati
ons for app(s): admin, auth, contenttypes, sessions.
web_1  | Run 'python manage.py migrate' to apply them.
web_1  | January 21, 2020 - 14:49:16
web_1  | Django version 3.0, using settings 'example_project.settings'
web_1  | Starting development server at http://0.0.0.0:8000/
web_1  | Quit the server with CONTROL-C.