What is a Docker Container?
Docker is an open source platform designed to build, distribute and run applications inside a container. A container is a virtual box that packages applications with dependent services and components. In comparison to the traditional virtualization functionalities of hypervisors, Docker containers eliminate the need for a separate guest operating system for every new virtual machine.
A Docker container enables rapid deployment with minimum run-time requirements. It also ensures better management and simplified portability while reducing the resource requirements for deploying new containers. This helps developers and system admins in rapid deployment of an application.
Docker Container Architecture
The architecture of a Docker container includes a physical machine with a host operating system. On top of the host operating system, a Docker engine is deployed, which helps create a virtual container for hosting applications. Docker engines create isolated containers on which applications can be deployed. Unlike a typical hypervisor solution, Docker eliminates the requirement of creating a separate VM for each application, as well as the requirement of a guest OS for each VM.
In hypervisor-based application virtualization, a virtualization platform (for example Hyper-V or VMware) is deployed on a physical server with a host OS. On top of the virtualization platform, virtual machines are created, each of which has an independent guest OS. On top of all these layers, the application is deployed. Hosting so many virtual machines, each having an independent guest OS, makes this architecture much more resource-intensive than Docker containers.
In Docker containers, applications are built directly over Docker engines, eliminating the need for a guest OS. This capability helps reduce overall system requirements such as CPU or RAM for hosting multiple guest operating systems. This also reduces deployment costs by reducing the need for compute resources as per application only. Unlike Docker containers, hypervisor-based applications require an additional guest OS along with the other dependencies for the actual application to run.
Docker Container Automation - Docker vs Hyper-V
Docker containers usually provide built-in tools to automate the process of container provisioning by leveraging source code from any existing application container. This takes care of services, dependencies, packaging and more. Docker also provides a broad range of pre-configured Docker images that help organizations in rapid deployment of application containers.
To accomplish this same set of tasks, any hypervisor solution will require a complex procedure involving cloning applications, along with their dependencies and tools, into an isolated package.
Ease of Application Migration - Docker vs Hyper-V
Docker allows distribution or shipment of applications across different environments in a Docker type of container, with all parts bound as a single package. For instance, to move an application from a development environment into testing and then production, the entire container can be packaged and migrated as a single entity; the application remains bound with all the environment configurations. This helps in migrating applications across different departments, between teammates, or through the cloud without any risk of breaking things.
In hypervisor solutions, packaging and migrating applications with all their dependent services and tools always risks environment breakdown.
Docker Isolation and Security - Docker vs Hyper-V
In Docker containers, each application or container is isolated from others, but they use the same root. This provides the advantage of simplified management, although it also leads to a few disadvantages. For instance, if the root is compromised, the host containers could be at risk. Hypervisor solutions, in contrast, provide more or less complete isolation, depending upon the requirements.
Docker containers - Types of Applications
- Applications that need to run on more than one cloud
- Applications that use microservices
- Applications that benefit from DevOps
Docker containers are not unlike other container technologies. However, Docker bundles key application components into a single container, which also makes these containers portable between different platforms and clouds. As a result, Docker is ideal for applications that need to run across various environments.
Developers using a fully encapsulated Docker container can create a more efficient distribution model for microservices-enabled applications. Developers and architects can build applications that run on multiple platforms, as well as both produce and consume microservices.