What is Docker and How to use it?

Docker is an open-source containerization platform that can be installed with a simple click. It allows developers to create, deploy, run, and manage applications within its containers. Docker’s software design makes it secure and reliable for its users. The major companies that use the respective tool are Spotify, Twitter, Pinterest, and PayPal. Let’s discuss this in detail.

Table of Contents:

What is Docker?
Why is Docker popular?
Essential Elements of Docker
What are Containers?
Docker Architecture
Docker Commands
When and Why Use Docker?

What is Docker?

Docker is a Platform as a service product (PaaS) for developing, packing, and running applications in containers.

Containers are lightweight, portable, and isolated units that store everything required to run an application, including the code, runtime, libraries, and system tools. It is one of the many tools that is used in DevOps to make the work of users a lot easier.

The issue that the development team commonly faces is that the project is completely functional in one’s system but when deployed to other systems it fails to give the expected output.

Here’s where Docker enters the picture; it gives the users space where they can code, create, and run a project without worrying about the configuration, system compatibility, and other constraints that are usually faced by the developers when they try to share their work with one or more systems.

It is the software that resolves the issue of an unsuitable environment for applications, sites, and products so that it can perform its task platform independently, irrespective of system compatibility.

Kindly go through our explanation video to get a better understanding!

Why is Docker popular?

Docker’s contribution to software development and deployment contributed to its rise in popularity. Some of the primary causes of Docker’s rise in popularity are as follows:

Portability: Docker allows developers to package their applications, including all dependencies, into a single lightweight container. It makes it simpler to ensure consistent performance across a range of computing environments.

Reproducibility: Software installs in development, testing, and production environments are guaranteed to be consistent when applications and their dependencies are contained within a container.

Efficiency: Docker uses a container-based architecture to make the most use of available resources. It allows the developers to execute multiple distinct apps on the same host machine.

Essential Elements of Docker

Among the essential elements of Docker are the following:

Docker Engine: This essential component of Docker manages container formation and administration.

Docker Image: The application code and dependencies are contained in the Docker Image, a read-only template used to create containers.

Docker Hub: A cloud-based repository called Docker Hub is used to locate and distribute container images.

Dockerfile: A script that includes instructions for creating a Docker image is called a Dockerfile.

Docker Registry: A storage distribution method for Docker images, the Docker Registry allows you to store the images in both private and public modes.

What are Containers?

A container is a unit that packages up the code, process, networking, OS, and all of its attributes, dependencies, and configuration.
One can create files and save them in a container. It is a place where the live application runs.
It is portable; now we can send this container to any system in which the docker is installed. It can be run, started, stopped, and deleted.
The container will work the same as it was working before shifting from one system to another.
Once a container is destroyed the data will be lost.

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Docker Architecture

Docker is built around the client-server architecture. With the help of Docker, we can manage containers, Docker images, data volume, and networks.

It is a monolithic application, which means one package will contain almost everything. Docker has components that have specific tasks to do:

1. Docker Client

It is a way of interacting with the docker.
The user sends the request in the form of commands; these commands can be used to build, run, pull, and maybe remove.
A Command Line Interface is responsible for the execution of the request that is made by users.

2. Docker Host

A Docker Host is a physical or virtual machine on which Docker is installed and used to run Docker containers. It serves as the foundation for containerization.

Operating System Compatibility: Docker Hosts can run on various operating systems, including Linux, Windows, and macOS. This compatibility ensures flexibility in choosing the host environment.
Docker Engine: The Docker Host requires the Docker Engine, which is responsible for managing containers. It facilitates the execution of containerized applications by handling container creation, networking, and storage management.
Resource Management: Docker Hosts allocate resources such as CPU, memory, and storage to containers, ensuring they run efficiently. You can configure resource limits for each container to prevent one container from monopolizing resources.
Networking: Docker Hosts provide networking capabilities for containers, allowing them to communicate with each other and external networks. Hosts can be configured to create custom networks, enabling different containers to connect securely or remain isolated.
Isolation: Containers on a Docker Host are isolated from each other, preventing interference between applications. This isolation ensures that applications within containers do not conflict or negatively impact one another.
Scalability: Docker Hosts can be part of a Docker Swarm or Kubernetes cluster to manage and scale containers across multiple hosts. This is essential for applications that require horizontal scaling to handle increased workloads.

3. Docker Image

The set of read-only files is known as Docker Image. Once created, it cannot be modified, it is used to build the Docker Containers.
It contains a small part of the operating system, which is required to run a docker container.
We obtain containers as an output when we use the docker run command to run the docker image.
An existing image, referred to as a base image, can be used to produce a new docker image.
Docker images are the blueprint of a container. One image can create multiple containers.
Examples of docker images are Ubuntu images, MySQL images, Java images, and images for applications, built in Node.js and using MongoDB.

4. Docker Registry

Docker Registry is like an online library for Docker containers. It’s a place where people store and share the software they’ve packaged into containers. Here’s why it’s important:

Image Storage: Think of Docker containers as packages of software. The Docker Registry stores these packages, making it easy for anyone to download and use them. It’s like a huge digital warehouse for all kinds of software.
Central Repository: It’s like a central hub for Docker images. You can find official images, which are like well-known books, and user-created images, which are like personal notes in this library. It’s the place to go when you’re looking for software in the Docker world.
Version Control: Just like you can get different editions of a book, Docker Registry keeps track of different versions of software. This way, you can choose the exact version you want, just like selecting a specific print of a book.
Security: It has security measures in place. You can’t just walk into this library and take any book. You need the right permissions, like a library card. It ensures that only authorized people can access the software.
Global Access: This library is accessible from anywhere, which is great for sharing and collaborating with people all over the world. It’s like a library that’s open 24/7, no matter where you are.

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5. Dockerfile

The Dockerfile offers instructions to create a Docker image using DSL (Domain Specific Language). Dockerfile specifies how to generate an image fast. Because the Docker daemon executes all of the instructions from top to bottom, you should generate a Dockerfile while you are building your application.

The background service that controls Docker containers on a system is called the Docker daemon, or just “Docker.”

It is a text document that includes the commands and instructions needed to assemble a Docker image when executed.

A Dockerfile is used to construct a Docker image.

6. Docker Hub

Docker Hub is a cloud-based repository service that allows users to upload and retrieve Docker Container Images from the Docker Hub at any time and from any location over the internet. In general, it facilitates finding and reusing photos. Among its advantages is the ability to store and distribute Docker images as well as deploy your images as a private or public registry.

The Docker Hub is mostly used by the DevOps people. For all operating systems, it is a free and open-source program. It functions similarly to storage, where we keep the pictures and retrieve them as needed. One should be aware of this when attempting to push or pull images from the Docker Hub.

Docker Commands

The world of technology has included Docker on a fundamental level. Let’s go over some fundamental commands to get you familiar with Docker:

docker search: This command can be used to search the Docker hub for images that are freely accessible. It will output the image’s name and description.
docker pull: To extract the named image, we use the pull command.
docker image: To find out which images are there in our local machine we write docker images as a command.
docker run: Suppose you have collected some images and now you have to create a container, then this command will come to work.
docker rm: used to remove a container.
docker logs: Helps to debug the docker container.
docker rename: It is used to change the existing name of the docker.
docker ps: Current running containers will be listed with the help of the docker ps command.
docker stop: To stop a working container, a docker stop command with the name of a container that is needed to stop is used.
docker restart: If you want to restart your already stopped container then this command will be used.

The above-mentioned command will help you to understand the workings of docker more clearly. Let’s further understand why we need docker.

When and Why Use Docker?

Using docker it makes the task easy in the technical field where you have to develop a site and also put configurations into it.
Docker lets you ship faster, flawlessly move code and also save resources because of its optimality.
Docker provides a robust environment for the application that is to be built.
It provides the application with an environment that is robust enough to build.
Containers are easy to deploy; if an error occurs, it will be easy to identify, and rolling back to the previous state can be done.

To create a website that utilizes advanced and diverse technologies, it is advised to use Docker.

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Conclusion

Docker is used for its simplicity and accessibility, making it a valuable resource for developers of all levels. Whether you’re new to Docker or an experienced user, its capabilities empower you to navigate the ever-evolving surroundings of software development.

As we’ve explored Docker’s world, with topics like Docker images, containers, Dockerfiles, Docker Hub, Docker Compose, and Docker Registry, we’ve uncovered a super useful tool.

If you’re interested in learning more about Docker, consider delving into our DevOps course.