1. Introduction

Goal of the Tutorial

This tutorial will guide you on how to build Docker images from a Dockerfile, how to tag these images for better organization, and how to manage images on your system.

What You Will Learn

By the end of this tutorial, you will be able to:
- Understand what Docker images are and how they work
- Build a Docker image from a Dockerfile
- Tag Docker images for better organization
- Manage Docker images on your system

Prerequisites

Before starting with this tutorial, you should have Docker installed on your system. Some basic understanding of Docker would be helpful but is not required.

2. Step-by-Step Guide

Docker Images

Docker images are lightweight, standalone, executable packages that include everything needed to run a piece of software, including the code, runtime, libraries, environment variables, and config files.

Building Docker Images

To build a Docker image, you need to create a Dockerfile. A Dockerfile is a text document that contains all the commands a user could call on the command line to assemble an image.

Here's an example of a simple Dockerfile:

# Use an official Python runtime as a parent image
FROM python:3.7-slim

# Set the working directory in the container to /app
WORKDIR /app

# Add the current directory contents into the container at /app
ADD . /app

# Install any needed packages specified in requirements.txt
RUN pip install --no-cache-dir -r requirements.txt

# Make port 80 available to the world outside this container
EXPOSE 80

# Run app.py when the container launches
CMD ["python", "app.py"]

Then, you can build the image using the docker build command:

docker build -t your-image-name .

The -t flag lets you tag your image so it's easier to find later.

Tagging Docker Images

Tagging Docker images can help you keep your images organized. You can tag an image when building it with the -t option, or you can use the docker tag command to tag an existing image.

Here's an example of how to tag an image:

docker tag your-image-name your-username/your-image-name:tag

Managing Docker Images

You can manage your Docker images using various Docker commands:

• docker images lists all images
• docker rmi Image removes an image
• docker pull Image pulls an image from a registry
• docker image prune removes unused images

3. Code Examples

Building Docker Image

Create a Dockerfile with the following content:

# Use an official Python runtime as a parent image
FROM python:3.7-slim

# Set the working directory in the container to /app
WORKDIR /app

# Add the current directory contents into the container at /app
ADD . /app

# Install any needed packages specified in requirements.txt
RUN pip install --no-cache-dir -r requirements.txt

# Make port 80 available to the world outside this container
EXPOSE 80

# Run app.py when the container launches
CMD ["python", "app.py"]

Then, build the image with the docker build command:

docker build -t my-python-app .

Tagging Docker Image

Let's say you want to tag the image you just built with the version v1.0. You can do this with the docker tag command:

docker tag my-python-app my-username/my-python-app:v1.0

Managing Docker Images

To list all Docker images, you can use the docker images command:

docker images

You can remove an image using the docker rmi command:

docker rmi my-python-app

4. Summary

In this tutorial, we covered the basics of Docker images, including how to build them from a Dockerfile, how to tag them for better organization, and how to manage them on your system. The next step is to learn about Docker containers, which are the running instances of Docker images.

5. Practice Exercises

1. Build a Docker image from a Dockerfile that runs a simple Node.js application.
2. Tag the image with your username and the version v1.0.
3. List all Docker images on your system and remove the image you just built.

Good luck with your Docker journey!