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Containers and virtualization have changed the way we think about running applications. They've made things faster, more efficient, and much easier to manage—especially as environments grow more complex. In this chapter, we'll take a closer look at what containerization is, how it compares to virtualization, and why it's become such a big deal in the world of modern infrastructure.Containerization is a lightweight way to package and run software consistently across environments—from a laptop to production. Unlike virtual machines, which each run a full operating system, containers share the host's kernel, making them faster and more efficient.While both containers and VMs allow multiple apps on one machine, they use different approaches. That distinction affects performance, resource use, and deployment speed—topics we'll break down with clear examples. It's also worth noting...

Technical requirements

In this chapter, you will need:

• Internet Access
• Shell Terminal and SSH Client
• Running CentOS 9:
• Based on Type 2 Hypervisor – VMWare Fusion or VirtualBox
• Based in Private or Public Cloud
• Firefox or another modern Web-browser

Benefits of Containerization

Containerization has reshaped the way we build, run, and manage applications. With tools like Docker, it's now easy to package an app—along with everything it needs—into a compact, portable container that runs anywhere.In the sections that follow, we'll look at the key benefits that have made containers such a vital part of modern software development.

• Consistency and Portability: Inconsistencies between dev, test, and production are common and often cause problems. Containers solve this by packaging everything the app needs, so it runs the same everywhere—on your laptop, on-prem, or in the cloud. With Docker images, you build it once and run it anywhere with confidence.
• Agility and Speed: Containers start fast and use less space because they share the host's operating system, unlike virtual machines that run a full OS. This makes development quicker, deployments faster, and updates easier.
• Resource Efficiency and Density...

Containerization vs virtualization

While both containerization and virtualization aim to optimize resource utilization and easy application development and deployment, they operate at fundamentally different levels and have distinct use cases. Let's clarify the differences.

Containers and microservices

Containerization took off alongside the move to microservices. Instead of building one big, all-in-one app, microservices break things down into smaller units that can be built, deployed, and updated on their own. Containers make this much easier — they're a great way to package and run each service separately. This setup comes with a bunch of advantages, like:

• Granular Isolation and Deployment: Each microservice, with its specific dependencies, can reside within a dedicated container. This promotes isolated environments, preventing conflicts and allowing independent updates without impacting other components of an application.
• Scalability by Design: Microservices work best when you need to scale specific functions of an application under load. Containers facilitate rapid scaling by quickly replicating instances of the microservice in question. Orchestration platforms like Kubernetes (on which OpenShift 4 is built) excel at managing these containerized...

Lab Environment

There's a saying "One good test is worth a thousand expert opinions". We follow the same principle in this book and whatever we talk we try to verify in the lab and urge you to follow the same advice. Trust but verify.In Chapters 1 and 2, we mainly use a single Instance of CentOS 9. In later chapters, we are going to utilize a mix of OpenShift Local and OpenShift 4 UPI (User Provided Infrastructure) multinode cluster built in a VMware vSphere environment. You don't need a dedicated server with a lot of resources to follow the labs in this book and can complete most of the tasks on your laptop that have enough CPU and RAM, but we encourage you to have your own dedicated servers to be able to run a full OpenShift 4 installation.

Podman overview

Containers are transforming software development. They package applications and their dependencies into portable units, ensuring they run the same way on any compatible system - be it your laptop or a massive cloud-based cluster. This streamlines deployment, promotes consistency, and empowers microservice architectures. Podman offers a unique way to harness the power of containers.

Podman vs Docker

The world of containerization often centers around Docker, the tool that brought containers into the mainstream. Podman, however, provides a good alternative that meets the demands of developers and administrators. Let's look at their core differences, advantages, and when to choose one over the other.

• Docker's Daemon: In contrary to Podman, Docker relies on a central, long-running daemon process (dockerd). This daemon handles image management, launching containers, networking, and most interactions with the Docker command-line tool (docker).
• Podman's Liberation: Podman eschews the daemon. Instead, it uses the fork/exec model: it spawns child processes when necessary for running containers and managing images.

Security plays a huge role in the world of containers and while docker came as first comer, it couldn't address all the issues and demands of the real world needs as it evolved, this is where podman comes into...

Summary

In this chapter, we quickly went through what containerization is how it benefits the modern world by itself and it lives together and differs to virtualization.Most importantly we discussed how containers are working in OpenShift 4 as it is going to be the main product we are using in this book. This book is full of practical exercises, so we need to build multiple lab environments where one of the most simple and accessible ones is to run on the local laptop as a VM. You should have brought up a Linux VM and completed several practical tasks with Podman basics. We went over essential concepts such as Images, Containers and Pods and how they work together. From there we compared root vs rootless containers, their different implementation scenarios and outcomes.Finally, we did a comprehensive comparison of Docker vs Podman from different angles including architecture, security, development points of view.In the next Chapter, we will go into brief history of Kubernetes, how it...

References

• [1] VMware ESX Installation and Setup - https://techdocs.broadcom.com/us/en/vmware-cis/vsphere/vsphere/9-0/esx-installation-and-setup.html
• [2] Broadcom Support Documents and Downloads - https://docs.broadcom.com/
• [3] Enabling virtualization on AMD64 and Intel 64 - https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/9/html/configuring_and_managing_virtualization/assembly_enabling-virtualization-in-rhel-9_configuring-and-managing-virtualization#proc_enabling-virtualization-in-rhel-9_assembly_enabling-virtualization-in-rhel-9
• [4] Windows Server 2025 and FREE Hyper-V Dream - https://www.starwindsoftware.com/blog/windows-server-2025-and-free-hyper-v-dream/
• [5] Install Hyper-V - https://learn.microsoft.com/en-us/virtualization/hyper-v-on-windows/quick-start/enable-hyper-v
• [6] Oracle VirtualBox: User Guide for Release 7.1 | Chapter 2. Installation Details - https://www.virtualbox.org/manual/ch02.html
• [7] Download CentOS Stream - https://www.CentOS.org/download/
• [8]...

Quiz

Test your understanding of Podman with this quick quiz. Remember, some questions may have more than one correct answer!

1. Which of these statements accurately describe Podman's architecture?
   1. It relies on a long-running daemon process like Docker does.
   2. It utilizes a fork/exec model for managing containers and images.
   3. It requires root privileges for all container operations.
2. If you are already familiar with Docker commands, you'll feel right at home with most of Podman's basic usage.
   1. True
   2. False
3. Which of these tasks can Podman help you with? (Select all that apply)
   1. Building container images
   2. Inspecting container images stored in remote registries
   3. Orchestrating large-scale, multi-container applications across a cluster
   4. Running a containerized database server
4. In a Podman context, what is a pod?
   1. A standalone container with its own network and storage resources.
   2. A group of closely related containers sharing a network namespace and potentially storage.
   3. A set of commands...

Answers

1. B. Unlike Docker, which operates on a client-server basis, Podman launches a child process using fork() system call and then uses exec() to replace it with a container process, eliminating the need for a server and improving security.
2. A. Most Podman's commands maintain backward compatibility with Docker, easing transition.
3. A, B, and D. To manage a complex application that consists of many interacting microservices running in containers, you will need an orchestrating engine, like Kubernetes, or its derivatives (OpenShift being one of them).
4. B. Each pod contains one or more containers that share Linux kernel namespaces, for example network, which means that processes inside the same pod can communicate with each other through local network (localhost).
5. A. Due to its daemonless architecture and non-reliance on root access, Podman is a better choice when a better security posture is desired.