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Containers vs. Virtual Machines: Explaining the Differences [2023]

Containers vs. Virtual Machines
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Are you just getting started with visualization tools? Or hacking your way through the technology conversation on containers and virtual machines.

Virtualization entails the process where singular resources like the RAM, CPU, networking, and disks can be “virtualized” and regarded as multiple resources. The key difference is that containers can only virtualize software layers built above the operating system level. In contrast, virtual machines can virtualize entire machines to the hardware layers.

While there is a clear distinction, there is a list of similarities between containers and virtual machines, including how they improve IT efficiency, avail portability to applications, enhance DevOps, and the software development life cycle (SDLC). More about this later.

This post breaks down containers and virtual machines, dives into the benefits of both, and concludes with a note on choosing the right tool based on your needs. It also assumes you have the prerequisite knowledge of containers and virtual machines. If you haven’t, it is still an excellent place to start.

History of Virtualization

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Before the proliferation of containers, virtual machines were the only solution for isolating environments within a physical infrastructure. But it was not until 2013 that Docker released their first containerization software.

And since then, you may have noticed the spanning interest in containers and how they shape the cloud computing landscape.

Many developers have gained more interest, particularly in the benefits of the agile development offered by containers. However, you should note that containers and virtual machines are built on optimizing resources in existing physical infrastructure.

How Virtualization Works

Virtualization involves using software to create an abstraction layer over computer hardware, allowing the hardware elements, say particularly from one computer, to be divided into multiple computers. Such software is called a hypervisor.

Hypervisor allows various operating systems to run concurrently, sharing common physical computing resources. When used on physical computers or servers in data centers, it will enable physical computers to separate computer operating systems (OSs) and applications from the hardware. Afterward, it can divide itself into multiple “virtual machines.”

What is a Container?


Containers are a lightweight, agile method for handling virtualization. And since they do not need hypervisors, they entitle you to faster resource provision and speedy availability for new applications.  

You can also view containers as software packages containing dependencies required to execute the managed application software application.

The dependencies include system libraries, external (third-party) code packages, and the inclusion of all other operating system-level applications. All dependencies included in a container exists in stack levels higher than the operating systems.

Pros 👍

  1. Iteration Speed – Containers are lightweight and only include high-level software; they are easily adjustable, and you can quickly iterate on them. Containers also offer speedy software delivery due to test-driven development and deployment availability.
  2. Robust Ecosystem – In most cases, container runtime systems provide an already-hosted public repository of premade containers. The repository contains various popular software applications like the database and messaging systems that can be downloaded and deployed, cutting time for development teams.
  3. Scaling – Containers are preferred for their ability to handle large volumes of workload and traffic. Information technology (IT) experts can use containers to manage and provide cloud infrastructure in a resource-efficient facilitating flexible usage.
  4. Microservices – Containers are ideal if you want to deploy multiple microservices. Microservices involve smaller components that are part of your primary application or software. When you package each microservice as a container, you are entitled to seamless deployment, scaling, and management.

Cons 👎

  1. Shared Host Exploits – Since containers share a common underlying hardware system built below the operating system layer, there’s a possibility that an exploit in one container could break and spread out, affecting the underlying hardware. Also, the fact that most containers have public repositories of prebuilt containers introduces a security risk. The risk is realized in cases where a compromised or exploited public image acts as a vulnerability risking cybersecurity attacks.
  2. Runs Only One Operating System – If you are the kind that uses only one operating system, containers allow you to run earlier versions, which is a good thing. However, containers aren’t the best option if you are targeting different operating systems.

Here are some well-known container providers:

  1. DockerDocker is the most world widely adopted container solution. Docker Hub is a large repository for the most popular containerized applications. You can download containers from Docker Hub and deploy a local Docker runtime.
  2. Linux Containers (LXC) – The Linux Containers project is behind the Linux open-source container runtime. LXC isolates operating system processes from each other. If you dig deeper into Docker, you’ll discover that Docker uses LXC in its underlying architecture.

What is a Virtual Machine?


Virtual machines (VMs), on the other hand, are large (heavy) software packages providing complete emulation of low-level hardware equipment like the central processing unit (CPU), disk, and networking devices.

VMs allow you to run multiple machines on different operating systems yet still in a single computer. As mentioned earlier, hypervisors are how VMs interact with physical computers. Hypervisors separate VMs from each other and allocate resources like memory and processors among them.

Pros 👍

  1. Full Isolation Security – Virtual machines operate in isolation as fully standalone systems, immune to exploits and interruptions from other virtual machines. If an attack is launched on an individual virtual machine, it is isolated, making it impossible to contaminate neighboring virtual machines.
  2. Interactive Development – Often, containers are static definitions of expected dependencies and configurations needed to run the container. Virtual machines are dynamic, allowing for interactive development. Once you have specified your hardware needs, consider the virtual machine a bare-bones computer. You can manually install software and use the virtual machine to capture the current state configuration. The virtual machine snapshots can be used as a version control and, if needed, to restore the virtual machine to a specific time software or spin up additional machines with a required configuration.

Cons 👎

  1. Iteration Speed – Virtual machines are full-stack software and thus take time to build. Modifications in a virtual machine snapshot may take time to iterate and validate that the recent updates are behaving as expected.
  2. Storage Size Cost – Drawing from the fact that VMs are full-stack software again, you probably expect them to be significant. Yes, they take up much storage space and grow quickly to gigabytes. The effect is a shortage of space on either the machine hosting the VMs.

Here are a few popular virtual machine vendors:

  1. VirtualboxVirtualbox is one of the most established virtual machine platforms. The Virtualbox ecosystem has additional tools for developing and distributing virtual machine images. It is a free and open-source architecture emulation system owned by Oracle.
  2. VMwareVMware is built on the x86 architecture hardware and is a publicly traded company. This solution comes with a hypervisor to deploy and manage virtual machines. It is preferred for its robust user interface (UI) for managing virtual machines and an efficient enterprise tool offering support features.

Containers vs. Virtual Machines

While virtual machines have been around for as long, they are being replaced by containers for similar purposes. You have seen the pros and cons of both technology stacks. Here are the primary differences.

FeatureContainers Virtual Machines
Large and less portable based on each VM having its operating system. Virtual machines take up large space, measured in gigabytes.
VMs are not portable.
Do not have their own operating system.Have their own operating systems and thus perform extra tasks including; running programs incompatible with the host OS, multiple programs on different operating systems, and executing applications that cannot share operating system resources and functionalities.
Size and portabilitySmall and portable dues to the sharing operating system. Containers take up space measured in megabytes.
Containers can be moved across different computers.
Containers execute faster than virtual machines due to their already-running operating system. It takes seconds to run.
Boot-time speedVMs are slow as they have to boot their own operating systems first. It takes several minutes to boot.The price of VMs is relatively higher—the high need for resources and complexity tiers and a high cost.
Access to resourcesContainers have access to all resources in the Host machine.Virtual machines use the specific resources allocated to them by the hypervisor.
Security Less secure. Containers running on a shared host operating software are vulnerable when the host OS is compromised.Complex deployment; the level of complexity of VMs indicates that they need more time for development. Deployment is no different.
DeploymentEasy deployment; this is because of its nature, “self-contained,” and has slight ease in deploying, moving, or upgrading.The price of VMs is relatively higher. The high need for resources and complexity tiers, along with it, is a high cost.
CostThe price of containers is relatively lower because there are fewer requirements than in the VMs.The price of VMs is relatively higher—the high need for resources and complexity tiers, along with it a high cost.

How to Use Containers and Virtual Machines Simultaneously

If you have been wondering whether or not it is possible to use containers and virtual machines together, the answer is yes. Although, the practical cases are limited. You can create a VM to emulate specific hardware configurations and install an operating system.

Once your VM boots the operating system and is fully functional, you are now equipped with an emulated computation system with specific hardware on which you can install containers.

A good example to illustrate this configuration is experimenting with a system for chip deployments. Some popular methods for on-chip computation devices like BeagleBone development boards and Raspberry Pi can be emulated as virtual machines to experiment with operational (running) containers before testing on actual hardware.

Another advantage of using the union of containers and virtual machines is to increase security. For instance, you can deploy containers in virtual machines. Consider an example where ten containers are deployed on one computer to demonstrate how this is helpful.

If the computer gets compromised, you are at risk of affecting the ten containers. The solution is achieved by distributing the ten containers across ten virtual machines. If one virtual machine gets compromised, the other parts of the system application still usually operate.

Final Words

If you have precise hardware specifications for your project or are developing on one hardware and still targeting another, like Windows vs. MacOS, it would be best to use virtual machines. In other cases where the requirements are “software only,” the best option would be using containers.

In most cases, your needs will be satisfied by either of your choices. To pick the best one, understand your resource needs and the associated trade-offs. The right tool will therefore depend on your project.

If you need fast, efficient deployment, containers are your best choice. If your organization needs to virtualize a complete operating system on hardware, VMs are the best. And if you are looking to maximize security, a combination of both would be best; however, it has an associated cost.

Lastly, both containers and virtual machines are valid solutions. However, your specifications should be the decisive guiding factor. If you still need more guidance and profound understanding, I’d suggest heading to Docker vs. virtual machine.

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