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Easy To Understand Docker

Throughout this article, we will explain Docker in an easier way. 
 
What is Docker?
 
Open source software platform Docker delivers an environment for creating, deploying, and managing virtualized application containers on a common operating system (OS) with an ecosystem of allied tools. Developers can build lightweight and portable software containers with Docker to simplify application development, testing, and deployment. Using OS-level virtualization, it enables software packages called containers to be delivered over the internet through a set of platform as a service products. A container is isolated from one another and bundles its own software, libraries, and configuration files. It can communicate with other containers through defined channels.
 
What it can do?
 
It is possible for Docker to package an application and its dependencies into a virtual container that runs on Linux, Windows, and macOS computers. It provides the ability to run the application on-premises, in a public cloud, or even in a private cloud. Using Linux’s resource isolation features (cgroups and kernel namespaces) along with a union-aware file system (such as OverlayFS), Docker allows containers to run within a single Linux instance with no overhead associated with starting and maintaining virtual machines. On macOS, Docker uses a Linux virtual machine to run the containers.
A single server or virtual machine can run several Docker containers at the same time thanks to Docker’s lightweight design. An analysis conducted in 2018 found that a typical Docker use case involves running eight containers per host, and a quarter of analyzed organizations run 18 or more containers per host.
By implementing a high-level API, Docker provides lightweight containers, which run processes in isolation. As Docker containers are standard processes, it is possible to use kernel features to monitor their execution, including Interfering with system calls using strace.
 
What is a container?
 
An application container is a standard unit of software that packages up code, as well as its dependencies, so that it can run reliably from one environment to another. In Docker, a container image is a lightweight executable package that contains all the components necessary to run an application, including code, runtimes, system tools, libraries, and settings. A container image becomes a container during runtime, and for Docker containers, images become containers upon execution on Docker Engine. Whether on Linux or Windows, containerized software will always run the same, regardless of the infrastructure. In a container, software is isolated from its environment and is always operational regardless of whether it is development or staging.

TBased on Docker Engine, there are three types of Docker containers:
 
Standard: With Docker, containers became portable anywhere, establishing an industry standard.
 
Lightweight: By sharing the machine’s OS system kernel, containers do not require an OS per application, resulting in higher server efficiency and lower server and licensing costs.
 
Secure: It is safer to run applications in containers and Docker is industry-leading in isolation by default.
 
Components Tools
 
Three components of Docker’s software as a service are:
 
Software: Dockerd, the Docker daemon, is a persistent process that manages Docker containers and manages container objects. Requests are received via the Docker Engine API by the daemon. CLI, the command-line interface provided by the Docker client program, allows users to interact with Docker daemons.
 
Objects: 
1. An application in Docker is composed of various Docker objects. Containers, images, and services are the three most common Docker objects.
2. Docker containers are encapsulated environments designed to run applications. Docker API or Docker CLI are used to manage containers.
3. Docker images are read-only templates used to build containers. In order to store and ship applications, images are needed.
4. Containers can be scaled across multiple Docker daemons using Docker services. The result is a set of cooperating daemons that communicate through the Docker API, called a swarm.
 
Registries: An image repository for Docker is called a Docker registry. Clients of Docker can download (“pull”) images from registries for use, or upload (“push”) their own images. Public and private registries both exist. Docker Hub and Docker Cloud are the two main public registries. A Docker Hub registry is Docker’s default repository for images. In addition to notifications, Docker registries permit the creation of events-based notifications.
 
We hope this article gave you a better understanding of Docker. 
 
That’s it!
 
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