How is Docker different from a Virtual Machine?

When we speak about efficient utilization and proper allocation of computer resources, both virtual machines, and Docker containers are effective in their own ways. In the past few years, Docker containers have gained tremendous popularity among organizations of all sizes. It is very important to understand the use-cases and purposes that they both serve if you want to decide which of the two is better for your requirements. In this article, let’s discuss the basic differences between Docker containers and virtual machines.

However, before we start the discussion make sure that you have the basic knowledge of what Docker is. You can refer to our tutorial on Docker. So without any further ado, let’s get started.

What is Docker?

Docker is an open-source and freely available platform that offers tools and utilities to create and manage containers. Docker also has its own registry which has tons of free as well as vendor-specific Docker images that are very useful. Some popular images include Nginx, Ubuntu. Python, Mongo, Apache, etc.

We can create isolated and packaged environments to build, test, and deploy applications using Docker. These environments are called containers. Containers essentially perform the same function as Virtual Machines but in a more efficient way. Containers sit on top of the operating system of the underlying host machine. Multiple containers share only the kernel space of the OS. The userspace for each of them is different. Containers use a set of namespaces and control groups to achieve this.

Containerization is not a new concept. The first time containerization was introduced by Linux. And it was known as LXC (Linux Containers). Later, Docker used its own technology called containerd and runc at multiple levels to implement containers. This made containers more portable and flexible.

Docker containers are very light in weight. They are just a few megabytes in size. Hence, it’s very easy to transfer or migrate code. It takes only a few seconds to create and run a container.

What are Virtual Machines?

Virtual Machines can be understood as an emulation of an entire system. It allows you to run multiple copies of a computer system inside a single host. All of them are isolated to one another and the processes of one VM do not affect the others. Each virtual machine has its own operating system and sits on top of the hardware of the underlying OS. They virtualize only the hardware and require their own OS. Hence, they eat up a lot of resources.

Virtual machines use a software called hypervisors that sits in between the hardware and guest VMs. VMs are generally used to carry out those tasks that might possess a risk of a security breach to the host machines. This is so because a VM is completely isolated from the host. Tasks such as working with a virus-infected file, beta testing of OS, etc. are the most commonly performed task on a virtual machine.

The important files running inside a VM are NVRAM, virtual disk, log, and configuration files. They are also popular in server virtualization. They are used to divide a physical server into multiple unique virtual servers and each server has its own virtual hardware, memory, disks, CPU, networks, etc.

There are two types of VMs - Process and System VMs. Some popular virtual machine providers are hyper-v, VirtualBox, Xen, VMWare, etc. Since each virtual machine has its own kernel, libraries, dependencies, file systems, etc., they take up a lot of resources to run, and hence, they are not so efficient. They have huge bootup times. These problems were solved by the inception of containerization.

Virtual Machine Vs Docker

Let’s discuss the highlighting differences between a Virtual Machine and Docker Containers.

Virtual Machine
They sit on top of the hardware of the underlying host.
They sit on top of the OS of the host.
Each VM has its own kernel space.
Containers share the kernel of the host.
They use virtual hard disks to achieve persistent storage.
They used mounted volumes to do so.
They are very huge in size, typically up to a few gigabytes
They are very lightweight and are up to a few megabytes.
Takes quite a lot of time to boot up.
Takes a few seconds to spin up.
Needs the expertise to set up and use virtual machines.
Requires simple Docker commands to set up a container.

Final Thoughts!

Both the Virtual Machines and Docker Containers have their own use cases. Docker Containers are suitable to run small applications and are generally used for testing applications. You can use containers especially when you want to maximize the number of programs to run and minimize the number of nodes. Whereas, Virtual machines are generally used to carry out those tasks that can cause a threat to the security of the underlying host.

In this article, we have discussed the basics of Virtual Machines, Docker containers, and their key differences. We certainly hope that you will now be able to decide which one caters to your requirements.

Updated on: 06-Aug-2021


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