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What is Docker Container? A Comprehensive Guide

what is Docker Container

A container is a common unit of software that packages up code and all its dependencies so the application operates fast and reliably from one computing domain to another. A Docker container image is a lightweight, standalone, executable package of software that contains everything needed to run an application: code, runtime, system tools, system libraries and settings.

Docker (both the technology and the company) started as a public PaaS offering called dotCloud. PaaS solutions were helped by container technology, which got new capabilities, such as live migrations and updates without hindrance. In 2013, dotCloud open-sourced its underlying container technology and called it the Docker Project. Increasing support for the Docker Project generated a large community of container adopters. Soon after, dotCloud became Docker, Inc., which in addition to donating to the Docker container technology, started to create its management platform.

Docker plays a key role in the DevOps lifecycle. It bridges the gap between development and operations by ensuring consistency across environments, speeding up deployments, and upgrading infrastructure as code.

What is a Container?

A container is an isolated environment for your code. This indicates that a container has no understanding of your operating system or your files. It runs on the atmosphere delivered to you by Docker Desktop. Containers have everything that your code must be to run, down to a base operating system.

Docker Containers vs Virtual Machines

The comparison between Docker (a containerization platform) and Virtual Machines (VMs) spins around the methods they employ to deliver virtualized environments for running applications. Understanding their differences is crucial for making informed decisions in software deployment and infrastructure management. Here’s a detailed comparison:

 Docker (Containerization)

  1. Architecture:

Docker utilises containerization technology. Containers package the application and its reliances together but use the same operating system (OS) kernel as the host system.

Lightweight, as they don’t need a full OS to run each application.

  1. Performance:

Increased performance and efficiency, as there’s no guest OS overhead. Containers communicate the host system’s kernel.

 Quicker start-up times compared to VMs.

3 Resource Utilization:

More efficient resource utilization as numerous containers can run on the same host without the requirement for multiple OS models.

Ideal for high-density environments and microservices architecture.

  1. Isolation:

Containers are separated from each other but transfer the host OS’s kernel, which may expose them to certain security exposures.

Eligible for scenarios where total separateness is not a critical condition.

  1. Portability:

Very portable as containers encapsulate all dependencies.

Easy to move across various environments (development, testing, production).

  1. Use Cases:

Ideal for continued integration and continuous deployment (CI/CD), microservices, and scalable cloud applications.

Virtual Machines (VMs)

  1. Architecture:

VMs run on hypervisors and simulate real computers, each with its own OS.

More serious due to the requirement to conduct a full OS for each model.

  1. Performance:

Slower performance compared to containers due to the overhead of operating different OS instances.

More extended start-up times for VMs.

  1. Resource Utilization:

Each VM needs a considerable amount of system resources (CPU, memory) due to the full OS.

Not as resource-efficient, particularly in high-density environments.

  1. Isolation:

Delivers strong seclusion as each VM is entirely different from the host and other VMs.

More secure in scenarios where full isolation of environments is essential.

  1. Portability:

VMs are less portable compared to containers. Driving them across environments can be more difficult.

The entire VM, including the OS, must be relocated.

  1. Use Cases:

Fit for running applications that need full isolation, and comprehensive protection, or are heavily dependent on distinct OS environments.

Comprehending these distinctions helps in choosing the right technology for your exact use case, whether it be for growth, testing, or production environments.

What are the Core Components of Docker?

There are the core components of docker:

  1. Docker Engine: Docker Engine is an open-source containerization technology for building and containerizing your applications. Docker Engine functions as a client-server application with A server with a long-running daemon process docked. APIs which identify interfaces that programs can use to speak to and lead the Docker daemon
  2. Docker Images: A Docker image is a file utilised to run code in a Docker container. Docker images act as a set of instructions to create a Docker container, like a template. Docker images also act as the starting point when using Docker. An image is similar to a print in virtual machine (VM) environments.
  3. Docker Containers: A container is an isolated environment for your code. This means that a container has no understanding of your operating system or your files. It operates on the environment provided to you by Docker Desktop. Containers have everything that your code must run in order, down to a base operating system.
  4. Docker Hub: Docker Hub is a container registry made for developers and open-source contributors to discover, utilise, and communicate their container images. With Hub, developers can host public repos that can be used for free or private repos for teams and enterprises.

How Docker Containers Work?

Docker containers are a strong tool for building, deploying, and operating applications by using containerization technology. Here’s a simplified explanation of how Docker containers work:

  1. Docker Engine:

Foundation: At the core of Docker is the Docker Engine, a lightweight runtime and toolkit that contains containers. The engine is what makes and runs containers based on Docker images.

  1. Docker Images:

Blueprints: Docker containers are created from Docker images. These images are the blueprints of the container. They have the application code, libraries, dependencies, tools, and other files required for an application to run.

Firm and Lightweight: Once an image is made, it does not alter. It evolves the immutable basis for a container. Images are generally very lightweight, which contributes to the efficiency of Docker containers.

  1. Building a Container:

Instantiation: When you run a Docker image, the Docker Engine makes a container from that image. This container is a runnable example of the image.

Isolation: Each container runs in separateness, having its own filesystem, networking, and isolated process tree separate from the host.

  1. The Container Runtime:

Execution: When the container forms, it runs the application or process specified in the Docker image. The Docker Engine assigns resources (CPU, memory, disk I/O, network, etc.) to the container as required.

Layered Filesystem: Docker operates a union filesystem to deliver a layered architecture. When a container is created, it adds a writable layer on top of the inflexible layers of the image. This layer is where all changes (like file creation, modification, and deletion) are written.

  1. Networking and Communication:

Network Isolation: Containers have their own network interfaces and IP addresses. Docker delivers network isolation between containers and between containers and the host.

Port Mapping: Docker helps you map network ports from the container to the host, letting external access to the services running in a container.

  1. Storage:

Continuous Data: While containers themselves are transient (temporary), Docker supplies methods to store data persistently using volumes and tie mounts, providing that crucial data can be maintained and transmitted across containers.

  1. Lifecycle Management:

Control and Automation: You can begin, prevent, transfer, and delete containers easily. Docker delivers commands to control the lifecycle of containers.

  1. Ecosystem and Integration:

Docker Hub and Registries: Docker combines with Docker Hub and other container registries where you can keep and transfer Docker images.

Orchestration Tools: For handling multiple containers across various hosts, Docker is used with orchestration tools like Kubernetes or Docker Swarm.

What are the Advantages of Using Docker Containers?

Here are the advantages of using Docker containers:

  1. Isolation and Safety: Containers deliver high isolation between applications and their dependencies. Each container operates in its environment, with its file system, network pile, and procedures. This makes running numerous applications on the exact host easy without stressing about competition or dependencies.
  2. Portability Across Different Environments: One of the main benefits of using containers is that they are completely transferable. Containers are created to be platform-independent and can be operated on any system that keeps the container runtime. This makes it comfortable to move applications between various environments, from development to test to production, without reconfiguring the setting.
  3. Resource Efficiency: Containers are lightweight, as discussed above and transfer the host system’s resources. This means numerous containers can operate on the same host without destroying many resources. This makes driving more applications on the same hardware potential, lowering costs.
  4. D. Scalability and Flexibility: Containers are fast, so they can be easily rotated up or down as required. Relying on the market, rising applications up or down are available. Container orchestration tools, such as Kubernetes, make it effortless to handle large numbers of containers and automate the scaling process.
  5. Consistency and Reproducibility: Containers provide a constant runtime environment for applications, regardless of the underlying system. This means developers can be sure that their code will operate similarly on any system keeping the container runtime.

What are the Common Use Cases for Docker Containers?

  1. Simplifying Configuration: Docker streamlines the operating and testing environment process which makes the task easier.
  2. Application Isolation: The control and design of isolated, lightweight containers are allowed by docker. These containers encapsulate the reliances of an application and make sure that it is compatible across numerous environments. 
  3. Microservices Architecture: Due to docker, the applications are segregated into shorter, effortless elements. The deployment and development of microservices-based architectures are handled by docker. 
  4. Continuous Integration/Continuous Deployment (CI/CD): One can complete ongoing delivery and integration due to docker. This is because the automated and rapid deployment of applications is facilitated by docker. 
  5. Development and Testing Environments: The developer tests their applications in reproducible, isolated containers. The process of operating and laying out testing environments is simplified by docker.

How to Get Started with Docker?

Follow these steps to get started, with Docker: 

  • First, we must Install Docker. 
  • Create the Docker Project
  • Edit the Python file 
  • Edit the Docker file 
  • Work on building your first Docker image.
  • Run the Docker Image
  • Deploy Your First Container

What are the Challenges and Considerations in the Docker Containers?

Docker container security is difficult because a typical Docker environment has many more moving parts that require security. Those parts include:

  •  You likely have multiple Docker container images, each hosting personal microservices. You probably also have multiple examples of each image operating at a given time. Each of those images and models ought to be connected and scanned separately.
  • The Docker daemon needs to be protected to maintain the containers it hosts safe.
  • The host server could be bare metal or a virtual machine.
  • If you host your containers in the cloud using a service like ECS, that is another layer to ensure.
  • Overlay networks and APIs that enable communication between containers.
  • Data volumes or other storage systems that are present externally from your containers.

The Future of Docker Containers

The future of Docker Developers is very encouraging. Docker is growing rapidly. Technology is extensive and the need for Docker software developers and programmers is also high in the market. Docker methodologies are changing with new tools and technologies coming in. It’s a huge and fast-growing area. Docker is highly paid but you need to be a master in Docker. It’s populated recently and demand for Docker is high in the market in comparison to other jobs. There are so many options available to choose as a career path in software development. Companies are currently moving towards a programmatic approach to application security, Docker development, and Containerization automation that embeds security in the early stages of the software development lifecycle.

What are the modules you will learn in Docker and Kubernetes?

You will learn modules like:

  • Container Basics
  • Docker images and public registry
  • Docker private registry
  • Docker networking
  • Docker storage
  • Building Docker image
  • Docker compose
  • Container orchestration and management
  • Kubernetes basics
  • Kubernetes architecture
  • Deploying highly available and scalable application
  • Kubernetes networking
  • Kubernetes storage
  • Advanced Kubernetes scheduling
  • Kubernetes administration and maintenance
  • Kubernetes troubleshooting
  • Kubernetes security

What are the exam details of Docker and Kubernetes?

Here are the exam details of Docker and Kubernetes:

  1. Docker Certified Associate (DCA):

The details of the DCA exam are as follows:

Exam Name

DCA (Docker Certified Associate)

Exam Cost 

195 USD

Exam Format

Multiple-choice questions

Total Questions

55 questions

Passing Score

65% or higher

Exam Duration

90 minutes


English, Japanese

Testing Center

Pearson VUE

Certification validity

2 years

  1. Kubernetes Certified Administrator (CKA):

The details of the CKA exam are as follows:

Exam Name

Kubernetes Certified Administrator (CKA)

Exam Cost

300 USD

Exam Format

Performance-based exam (live Kubernetes cluster)

Total Questions

15-20 tasks

Passing Score

74% or higher

Exam Duration

3 hours


English, Japanese

Testing Center

Pearson VUE

Certification validity

3 years

What is the eligibility of the Docker and Kubernetes?

Here is the eligibility for the Docker and Kubernetes training:

  • Graduation
  • Basic understanding of the IT industry
  • Basic understanding of installing and configuring applications
  • Understanding Virtualization and Linux
  • Fundamental knowledge of Cloud management 

Where to pursue the Docker and Kubernetes Course?

You can pursue Docker and Kubernetes courses from Network Kings:

  • 24/7 free access to the largest virtual labs in the world to practice all the concepts hands-on.
  • World-class instructor-led courses covering all the industry-relevant skills.
  • Free access to all recorded sessions as well as earlier batch sessions.
  • Exclusive doubt sessions with the Docker and Kubernetes engineers.
  • Free demo sessions to get a feel for the program.
  • Access to the online portal where you can monitor your academic progress.
  • Tips and tricks to crack job interviews.

What are the job opportunities after the Docker and Kubernetes course?

You can apply for several job opportunities in the DevOps and cloud computing space after completing the Docker and Kubernetes courses. These are:

  • Kubernetes Administrator
  • Docker Administrator
  • DevOps Engineer
  • Cloud Engineer
  • Site Reliability Engineer (SRE)
  • Infrastructure Engineer
  • Kubernetes Developer
  • Docker Developer
  • Microservices Developer
  • Cloud Operations Engineer
  • Cloud Solutions Architect
  • Kubernetes Consultant
  • Containerization Architect
  • Docker Consultant
  • Cloud Security Engineer
  • Continuous Integration and Deployment (CI/CD) Engineer
  • Systems Administrator
  • Cloud Migration Specialist
  • Cloud Automation Engineer
  • Cloud Platform Engineer

What are the salary prospects after the Docker and Kubernetes courses?

The salaries of Docker and Kubernetes Certified Administrators can vary widely depending on the country and the organization they work for. Here are some approximate salary ranges for these roles in various countries:

  • India: INR 6-15 lakhs per annum
  • China: CNY 150k-300k per annum
  • USA: USD 80k-150k per annum
  • UK: GBP 35k-70k per annum
  • Japan: JPY 6-12 million per annum
  • France: EUR 35k-70k per annum
  • Germany: EUR 40k-80k per annum
  • South Africa: ZAR 240k-600k per annum
  • Netherlands: EUR 45k-90k per annum
  • Singapore: SGD 50k-120k per annum
  • Australia: AUD 70k-140k per annum
  • Brazil: BRL 60k-120k per annum
  • Switzerland: CHF 80k-160k per annum


In conclusion, Docker containers convey a transformative technology in the landscape of software development and deployment. By encapsulating applications in lightweight, transportable, and self-sufficient environments. Docker not only facilitates the intricacies associated with software delivery but also improves the scalability, efficiency, and consistency across various computing environments.