Introduction

In this tutorial, we aim to compare and contrast two key technologies used in deploying applications: Virtual Machines (VMs) and Containers. This tutorial will provide a clear understanding of what VMs and Containers are, their similarities, differences, and their practical use-cases.

By the end of this tutorial, you should be able to:
- Understand what a VM and a Container are
- Know the differences and similarities between VMs and Containers
- Identify use-cases where you might choose to use VMs or Containers

Prerequisites:
- Basic understanding of how applications are deployed
- Basic knowledge of system architecture

Step-by-Step Guide

Virtual Machines

A Virtual Machine (VM) is an emulation of a physical computer system. VMs are based on computer architectures and provide the functionality of a physical computer. They run on a hypervisor which allows multiple VMs to run on a single machine. Each VM includes a full copy of an operating system, the application, necessary binaries and libraries - taking up tens of GBs.

Containers

Containers are an abstraction at the app layer that packages code and dependencies together. They share the OS kernel with other containers, and run as isolated processes in user space on the host operating system. Containers are not tied to any specific infrastructure – they run on any computer, on any infrastructure, and in any cloud.

VMs vs Containers

Use-Cases

• VMs are a better choice for running applications that require all of the operating system's resources and functionality when you need to run multiple applications on servers, or have high-security requirements.
• Containers are better when your goal is to maximize the number of applications using the same operating system and hardware, while isolating the applications from each other.

Code Examples

Here are some simple examples to show how to create a VM and a Container.

Create a VM

On a hypervisor like VirtualBox, creating a VM involves going through a wizard and selecting your options, such as the type of OS, hardware specs, etc.

vboxmanage createvm --name "My_VM" --register
vboxmanage modifyvm "My_VM" --memory 2048 --acpi on --boot1 dvd

In this example, we are creating a VM named "My_VM" and setting the boot order to boot from the virtual DVD drive.

Create a Container

With Docker, you can create a container by using a Dockerfile.

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

# Set working directory to /app
WORKDIR /app

# Copy the current directory contents into the container at /app
COPY . /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"]

This Dockerfile creates a Python container, sets the working directory, copies your local directory into the container, installs any dependencies, exposes a port for the application, and runs the application.

Summary

In this tutorial, we compared and contrasted VMs and Containers. VMs are emulations of a physical computer system, while Containers are an abstraction at the app layer that packages code and dependencies together. VMs have higher system overhead and are slower but are fully isolated. Containers have lower system overhead and are faster but share the OS kernel.

To further your understanding, you might want to look into specific tools and platforms such as Docker (for Containers) and VirtualBox (for VMs).

Practice Exercises

1. Install Docker and VirtualBox on your local machine. Try to create a simple VM and Container and note down your observations.
2. Try to deploy a simple web application in a VM and a Container. Compare the process and note down the differences and similarities.
3. (Advanced) Try to simulate a scenario where multiple applications are running in isolation. Use both VMs and Containers for this scenario and note down your observations.

Remember, practice is the key to mastering any concept. Happy Learning!