Understand Docker Containers With TheSecMaster

Some of our readers have requested information about Docker and container technology. We have decided to publish an article on Docker Containers to help many users understand the technical aspects of Docker and containers. In this blog post, we will clarify the concept of containers and their different types, explain what Docker is, explore the relationship between Docker and containers, discuss the appropriate use cases for Docker, delve into the problems Docker solves in development, address whether Docker replaces virtualization, explain the differences between Docker containers and virtual machines, and answer a few more questions that will aid in understanding Docker.

Before we delve directly into Docker, let’s begin by exploring containers, as it will make it easier to comprehend Docker if you are familiar with containers.

What is a Container?

A container is a lightweight and isolated environment that allows you to package and run an application and its dependencies. It encapsulates the software and all its dependencies into a single, self-contained unit that can run consistently across different computing environments.

Containers provide a consistent and reliable runtime environment, ensuring that an application will run the same way regardless of the host system. They achieve this by leveraging operating system-level virtualization, which allows multiple containers to run on the same host while remaining isolated from one another.

Each container includes the necessary libraries, binaries, and configuration files needed for the application to run successfully. This eliminates the common issue of “it works on my machine” by ensuring that the application’s runtime environment is consistent across different development, testing, and production environments.

The history and development of containers can be traced back to the early 2000s, although the concept of process isolation and virtualization dates back even further. Let’s explore the key milestones in the evolution of containers: The history and development of containers can be traced back to the early 2000s, although the concept of process isolation and virtualization dates back even further. Let’s explore the key milestones in the evolution of containers:

Since then, containers have gained widespread adoption and have become a fundamental building block in modern application development and deployment. They have revolutionized software delivery pipelines, enabling faster development cycles, improved resource utilization, and simplified deployment across diverse computing environments. The container ecosystem continues to evolve, with ongoing advancements in container runtimes, management tools, and security measures.

Types of Containers:

There are various container technologies available, each with its own unique features and use cases. And most of them were built on Linux Kernel. Here are some of the different types of containers:

These are just a few examples of container technologies available in the ecosystem. Each technology has its own strengths and use cases, and the choice depends on factors such as specific requirements, familiarity, and compatibility with existing infrastructure.

Containers can be further divided by their application. Let’s see the different types of containers from the application dimension.

What is Docker?

Docker is an open-source platform that enables developers to automate the deployment and management of applications within containers. It provides a standardized and efficient way to package applications and their dependencies into portable, self-contained units called container images.

If you read out previous sections, you could have learned the basic idea of the Docker.  To say in one sentence, Docker is a facade of Containers. Docker provides user interfaces to create, configure, and manage Containers. By the way, Docker uses LXC (Linux Containers). In essence, a docker is a high-level tool that provides several functionalities to operate Containers.

At its core, Docker utilizes containerization technology to create isolated environments where applications can run consistently across different computing environments. Containers created with Docker are lightweight, fast to start, and share the host system’s operating system kernel, while still maintaining process isolation from one another.

Docker introduced the concept of container images, which are built from a set of instructions called a Dockerfile. These images encapsulate everything needed to run an application, including the code, runtime, libraries, and system tools. They provide a consistent environment, ensuring that an application behaves the same way regardless of where it is deployed.

With Docker, developers can easily package their applications along with their dependencies into container images and distribute them to any environment where Docker is installed. Docker provides a robust ecosystem of tools and services, such as Docker Compose for managing multi-container applications and Docker Swarm for orchestrating container clusters.

The benefits of using Docker include improved application portability, scalability, and efficiency. It allows developers to build, test, and deploy applications in a reproducible manner, speeding up the development process and reducing the “it works on my machine” problem. Docker also simplifies the management of complex distributed systems and enables seamless deployment across various environments, including local development machines, on-premises servers, and cloud platforms.

Relationship between Docker and Container

To better understand, let’s see how Docker and Container are interrelated. We hope this section will help you feel better about concepts. Docker and containers have a closely intertwined relationship. Docker is a platform that facilitates the creation, distribution, and management of containers. It builds upon containerization technology and provides a user-friendly interface and toolset to work with containers effectively.

Containers, on the other hand, are lightweight and isolated environments that encapsulate applications and their dependencies. They provide a consistent runtime environment for applications, ensuring that they run consistently across different computing environments. Containers achieve this by utilizing operating system-level virtualization and leveraging features like namespaces and cgroups.

Components of Docker

Docker leverages the underlying containerization technology to create and manage containers. It introduces several key components that simplify working with containers, including:

Docker simplifies the process of working with containers by providing an abstraction layer and a comprehensive toolset. It streamlines container creation, distribution, and management, making it accessible to a wider audience. While Docker is a prominent container platform, it is important to note that there are other containerization technologies and platforms available, each with its own features and benefits.

How Does Docker Work?

As you know, Containers, much like virtual machines, offer fully isolated environments where processes, services, network interfaces, and mounts can operate independently. However, the key distinction is that containers share the same operating system (OS) kernel. This sharing of the kernel ensures efficient resource utilization while maintaining isolation. Let’s explore this in more detail.

Docker Containers on Linux:

To grasp the significance of containerization, it’s essential to revisit fundamental concepts of operating systems. Operating systems like Ubuntu, Fedora, Suse, or Centos consist of two primary components: the OS kernel and a set of software.

The OS kernel acts as an intermediary between the hardware and software layers. In the case of Linux-based systems, the kernel remains the same across various distributions. It is the software layer above the kernel that distinguishes different operating systems, encompassing aspects such as user interfaces, drivers, compilers, file managers, and developer tools.

Suppose we have a system with Ubuntu as the underlying OS and Docker installed. Docker enables the execution of containers based on different OS distributions as long as they share the same Linux kernel.

For example, if the host OS is Ubuntu, Docker can run containers based on distributions like Debian, Fedora, Suse, or Centos. Each Docker container contains only the additional software that distinguishes the respective operating systems. The underlying kernel of the Docker host seamlessly interacts with all the supported OS distributions.

Docker Containers on Windows:

You don’t see any difficulties to run Linux Containers on a Linux Docker, that’s because Linux-based distributions share a common kernel. However, there are operating systems that do not have the same kernel as Linux, such as Windows. In the context of containerization, running Windows-based containers on a Docker host with a Linux kernel is not possible. To deploy Windows containers, a Docker installation on a Windows server is required.

It’s not uncommon for people to question the notion that Linux containers can run on a Windows environment. Some may even install Docker on Windows, run a Linux container, and claim that it works. However, the reality is that running a Linux container on Windows involves an underlying mechanism.

When Docker is installed on Windows and a Linux container is executed, it is not truly running on Windows. Instead, Windows operates a Linux container within a Linux virtual machine. In essence, it is a Linux container running on a Linux virtual machine within the Windows environment.

While it may seem like a disadvantage that Docker does not enable running different operating systems and kernels on the same hardware, it is essential to understand Docker’s primary purpose and its unique advantages.

Docker is not designed as a hypervisor to virtualize and execute diverse operating systems and kernels simultaneously. Instead, its core objective is to package and containerize applications, facilitating their seamless deployment and execution across various environments.

The true strength of Docker lies in its ability to encapsulate an application, along with its dependencies and configurations, into a container. This container can then be transported and executed anywhere, anytime, and in any quantity.

Containers vs Virtual Machines

People from Virtualization backgrounds may often end up in confusion. The problem is not with them, the problem lies in some similarities between both technologies. Containers and virtual machines (VMs) are both technologies used for the isolation and deployment of applications, but they differ in their approach and resource utilization. Let’s do a comparison between containers and virtual machines:

Containers:

Virtual Machines:

When and Why to Use Docker Containers?

Both Virtualization and Containers are powerful technologies, we should compare them with each other. They have their own pros and cons. It is good to utilize both in combine to reap the maximum output. Well, since this post is dedicated to Docker Container technology, let’s see when and why to use Docker Containers.

Docker containers are widely used in various scenarios and offer several benefits that make them a popular choice for application deployment. Here are some situations where using Docker containers is advantageous:

We hope this article helps Understand Docker Containers. We are going to end this post for now, we will cover more details in the upcoming sessions. Please keep visiting thesecmaster.com for more such technical information. Visit our social media page on Facebook, Instagram,  LinkedIn, Twitter, Telegram, Tumblr, & Medium and subscribe to receive information like this.