Docker: Introduction step-by-step guide for beginners DevOps Engineers.
Tags: docker, devops, awschallenge
Published: 2024-06-24 16:58:56

**What is a Docker?**
Docker is a popular open-source project written in Go and developed by Dot Cloud (A PaaS Company). It is a container engine that uses Linux Kernel features like namespaces and control groups to create containers on top of an operating system.

Docker is a Container management service. Is an Open Platform for developing, shipping & Running applications.

You can separate your applications from your infrastructure and treat your infrastructure like a managed application.

Docker combines kernel containerization features with workflow & tooling that helps you manage & deploy your application.


![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/flajhoowou7q8f3r5qic.png)

**Why Use Docker?**
With Docker, you can:

🔧 Build Once, Run Anywhere: Docker containers ensure your application behaves the same way in every environment, from your laptop to production servers.

🏭 Faster Deployment: Say goodbye to time-consuming setup processes. Docker's lightweight containers launch in a snap!

🚀 Scalability: With Docker, scaling your applications becomes as simple as hoisting the sails. 🎉

**Docker Architecture:-**


![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/fq6o4etshf0ick8b648s.png)

Docker uses a client-server architecture. The Docker client talks to the Docker daemon, which does the heavy lifting of building, running, and distributing your Docker containers.

The Docker client and daemon can run on the same system, or you can connect a Docker client to a remote Docker daemon.

The Docker client and daemon communicate using a REST API, over UNIX sockets or a network interface.

Another Docker client is Docker Compose, which lets you work with applications consisting of a set of containers

**Key Features of Docker**
**Containerization and Isolation:**

Docker allows you to create isolated environments called containers, ensuring that applications and their dependencies are encapsulated, reducing conflicts and promoting consistency.
**Portability:**

Containers built with Docker are highly portable, meaning you can run them on any platform that supports Docker, from local development machines to cloud servers.

**Version Control:**

Docker makes it easy to version and share containers, enabling collaboration between developers and streamlining the continuous integration and deployment (CI/CD) pipeline.

**Efficiency and Performance:**

With its lightweight architecture, Docker minimizes the overhead of virtualization, resulting in faster application start times and better resource utilization.

**Scalability:**

Docker's design allows for effortless scaling of applications, both horizontally and vertically, to handle changing workloads and demand spikes.

**Integration and Ecosystem:**

Docker integrates seamlessly with various tools and platforms, making it an essential part of the DevOps ecosystem.

**What is a Container?**

In the above image, two applications are running on the same machine. These applications are run in a container and any changes made on this container do not affect the other container. Each of them can have a different Operating System running on the same physical machine.

Containers are instances of Docker images that can be run using the Docker run command.

The basic purpose of Docker is to run containers.

You can create, start, stop, move, or delete a container using the Docker API or CLI. You can connect a container to one or more networks, attach storage to it, or even create a new image based on its current state.

A Docker container is an isolated, Secured shipping box produced or created when the docker image is run.

A container packages up the code and all its dependencies so the application runs quickly and reliably from one computing environment to another.

**What is a Docker Image**

A Docker Image is a read-only file with a bunch of instructions. When these instructions are executed, it creates a Docker container.

Docker Image is a read-only template, composed of the layered file system, needed to build a running docker container, basically the running instance of the image.

**What is a Dockerfile**
Dockerfile is a simple text file that consists of instructions to build Docker images.

**Why should you use docker?**
Containers allow a developer to package up an application with all of the parts it needs, such as libraries and other dependencies, and deploy it as one package.

Previously for developing purposes, we are using monolithic Architecture, but nowadays we are using microservices architecture, monolithic architecture is built as one large system and usually on a code base.

To overcome this we used Docker. built as a small independent module based on business functionality.

**Before –**
Monolithic application

Long development cycles

Single environment

Slowly scaling up

**Now -**
Decoupled services

Fast and iterative improvement

Multiple environments

Quickly scaling out.