Docker vs Virtual Machines

Introduction

Docker containers and Virtual Machines (VMs) are both technologies used to isolate applications and workloads, but they achieve isolation in fundamentally different ways.

The most important distinction is:

A Virtual Machine virtualizes a complete computer system, including a guest operating system, while a Linux container isolates application processes and shares the host Linux kernel.

This difference affects architecture, resource usage, startup behavior, operating-system compatibility, security boundaries, portability, and how applications are deployed.

---

1. Virtual Machine Architecture

A Virtual Machine is a virtualized computer running on physical infrastructure through a hypervisor.

A simplified architecture looks like this:

Each VM has its own guest operating-system environment and kernel.

---

Docker vs Virtual Machines — Comparison

Docker                                                                                  <->    Virtual Machine
Shares the host kernel                                                                        <->     Runs a separate guest
kernel Isolates application processes                                              <->     Virtualizes an entire machine
Generally lower overhead                                                                  <->     Generally higher overhead
Designed primarily for application packaging and isolation       <->     Designed for complete OS and machine virtualization