Before Docker: Prior to Docker, software applications were deployed on bare metal computers or virtual machines (VMs).

Installing on bare metal devices made it very impossible to transfer and upgrade the software. Because of these two restrictions, it was unable to respond quickly to changes in business cases.

VMs were introduced as a solution to the above problem. To meet demand and preserve resources, VMs may be cloned, replicated, transferred, and spun up and down.

However, virtual machines (VMs) are huge (in GiBs) and each one comprises a full operating system. Provisioning a virtual machine still takes some time. Finally, VM portability is restricted.

As a result, bare metal and virtual machines cannot provide the speed, agility, and cost reductions that fast-moving organizations require. Docker entered the market.

Docker that arrived with containerization technology simplified the job of IT engineers. Containers function similarly to virtual machines (VMs), but in a much more specialized and precise way.

VMs run as virtual environments on the same hardware with multiple operating systems and make use of a hypervisor. Docker, on the other hand, runs on virtualizations of the same operating system and uses an execution engine.



DockerVirtual Machine
Docker is a container-based model where containers are software packages used for executing an application on any Operating System.VM use Hypervisor which allows virtualizing the user space along with the kernel space of an Operating System.
Docker container shares host OSVM shares guest OS
Boots in a few secondsThe booting process takes a few minutes
Docker runs on Execution EngineVM runs on Hypervisor
No space is needed to virtualize, hence uses less memory compared to VMRequires entire Operating System to be loaded before starting the surface of Guest OS
Complex usage mechanism consisting of both third-party and docker-managed toolsTools are easy to use and simpler to work with
Prone to adversities as no provision for the isolation systemInterference possibility is minimum because of the efficient isolation mechanism.
Easy and used across all platformsComparatively lengthy as separate instances are responsible for the execution