Virtual machine vs container: what’s the difference?


Virtual machines and containers are types of virtualization that allow applications to be deployed in environments isolated from the underlying hardware.

These technologies are often used in large IT projects to reduce costs and facilitate the deployment of programs on different platforms. A virtual machine is also useful for trying out new operating systems.

One problem with these concepts is that they are very similar, which makes it difficult to choose between them.

So what exactly is the difference between a virtual machine and a container?

What is a virtual machine?

A virtual machine is a virtualization of a computer. Virtual machines allow you to use a single computer to run what appear to be multiple computers, each with its own operating system.

Virtual machines are created using hypervisors. It is software that sits between a virtual machine and the underlying hardware. The hypervisor takes the resources of the underlying hardware and partitions them to dedicate them to individual virtual machines.

The result is multiple environments that use the same hardware but behave as if they are completely isolated from each other.

What is a container?

A container is similar to a virtual machine. But instead of virtualizing an entire computer, a container virtualizes only software above the operating system level.

Containers are lighter because they don’t need their own operating systems. To put this in perspective, they are usually measured in megabytes rather than the gigabytes associated with virtual machines.

They also do not need a hypervisor and can be placed directly on top of the host operating system. Each container then shares the kernel of the host operating system.

Although smaller than virtual machines, containers are still designed to include all of the files needed to run an application. They include all dependencies and runtime libraries. This allows an application inside a container to be run anywhere.

What is the difference between a virtual machine and a container?

Virtual machines have been around the longest, but they have been replaced by containers for certain purposes. Each technology, however, has its own advantages and disadvantages. The right tool for the job therefore depends on the specific project. Here are the main differences.

1. Virtual machines provide a separate operating system

Due to their own operating system, virtual machines can perform a number of tasks that are not possible with containers.

  • You can run programs that are not compatible with the host operating system.

  • You can run multiple applications in different operating systems.

  • You can run multiple applications that cannot afford to share operating system features and resources.

2. Containers are smaller and more portable

Sharing an operating system dramatically reduces the amount of code needed to run a container. Containers are therefore significantly smaller than virtual machines, often occupying only a few megabytes.

This potentially makes containers much cheaper, as you can install multiple containers on a single server. It also makes the containers much more portable.

Containers can be easily transferred between computers, IT environments, and the cloud. This makes them especially useful for teams that want to collaborate on a single app while using different environments.

3. Containers start up faster

Containers can be launched much faster because the operating system is already running, unlike launching a virtual machine, which involves starting a new operating system.

This allows containers to start up in seconds, whereas virtual machines typically take a few minutes.

Because containers use fewer resources, they also allow some applications to run faster.

4. Containers have access to all resources

Virtual machines have specific resources allocated to them by the hypervisor. This can be useful for resource-intensive applications, but it can also be inefficient when allocated resources are not being used.

Containers have access to all of the underlying hardware resources and therefore do not pose this problem. Therefore, containers are generally the best choice for applications where the required resources are unknown.

5. Virtual machines are more secure

A virtual machine is completely isolated from everything else on a computer. A container is only isolated at the process level. This makes virtual machines more secure.

If the host operating system is compromised, any containers installed on top of it can also be compromised. In the same scenario, virtual machines would not be affected.

An exploit performed inside a virtual machine cannot affect anything outside of it. An exploit executed inside a container can potentially gain access to the rest of a system.

Should I use a virtual machine or a container?

Virtual machines and containers are very similar to each other, but they are not interchangeable. Therefore, some projects will offer a choice between the two while others will not.

You should use a virtual machine when you want to run applications that specifically require a new operating system. For example, the host operating system may not support the application.

A virtual machine should also be used when isolation and security are a priority.

In most other scenarios, a container will provide a lighter, faster, and more cost effective solution.

Can you use virtual machines and containers together?

If you want the functionality of virtual machines and containers, it is possible to combine the two. In this case, you launch a virtual machine and then deploy containers inside it.

This is particularly useful for security purposes. For example, imagine that you are running ten containers on a single computer. If this computer’s operating system is compromised, all ten containers may be affected.

Now imagine that you spread these ten containers across multiple virtual machines. If any of these virtual machines are compromised, only the containers inside will be affected and the others will function normally.

Are containers replacing virtual machines?

Containers are becoming more and more popular and for very good reasons. They accomplish many of the same goals as virtual machines, but they do so at a fraction of the size and potential cost.

Despite this fact, there are many situations where only a virtual machine will provide the desired functionality, which means that virtual machines, regardless of their size, will always be used to some extent.

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