INTRODUCTION
The concept of containerization technology dates back to 1979 with the introduction of the Unix version 7 and the chroot system. The chroot system was designed to limit an application’s access to a specific directory and marked the first step towards isolated processes that later evolved into today’s popular containerization technologies such as Docker, Podman, LXC, Rkt (Rocket), Containerd, and Buildah. We will see what containerization is, where we can use it, pros and cons of containers. From the below image, we can get a glimpse of containerization evolution.
What are containers?
In simple words, it’s a form of virtualization where applications run in isolated user spaces called containers. So instantly thoughts come to mind that what makes containers different from VMs (Virtual Machines). So, when we talk about containers, we use containerization software or engines like docker, podman, etc. We install this software on OS to avail containerization.
When we talk about VMs, we use a hypervisor. A hypervisor sits on top of an operating system. But we can also have hypervisors that are installed directly on the hardware. Hypervisors take physical resources and divide them up so that virtual environments can use them.
What is the difference between VMs and Containers?
For understanding this, let’s consider you have one system/computer running on Windows OS. You want to run VMs of ubuntu, Amazon Linux, and redhat. So, when you configure VMs you allocate specific hardware resources like CPU core, RAM, etc. When you start your VMs, the hypervisor allocates specified resources to that VMs. Here is one catch when you start VMs it will reserve computer resources that cannot be used by host applications i.e., windows applications. That means a host cannot use unutilized resources even if VMs are using fewer resources. That means resources are blocked for the period VMs are running.
On the other hand, we install a containerization engine on the OS level such as Docker desktop on windows. So, when you start the Docker desktop application and run a container, it will allocate the resources as per the container’s need. If a container requires few or more resources, it will allocate dynamically. This optimal utilization of resources gives the Base OS edge to allocate unutilized resources to other applications when needed or to perform other tasks.
Now we have a good understanding of the working of VMs and Containers.
What are the advantages and benefits of containerization?
1. Portability: Running containers creates a portable software package that is independent of the host operating system, ensuring uniform and consistent operation across all platforms and clouds.
2. Speed: compared to VMs, containers are faster. It takes less time to boot up the container.
3. Size: Containers are smaller in size, and the repository contains many options to choose from as per our needs. Like we can use alpine images for work that are small in size as compared to the original image.
4. Cost: Most containerization tools are open-source and can be used for free, making it easy to get started with just a simple installation.
5. Scalability: Containers are highly scalable. An application container can handle increased workloads by reconfiguring the existing architecture to enable resources using a service-oriented app design.
6. Fault Isolation: The container operates independently which ensures that even if one container is failed it won’t affect others. This assures that failed container will not cause downtime for another container that shares the same host.
7. Security: Containers provide security by isolating applications, and preventing the spread of malicious code. Fine-tuned security permissions can also be set to block unauthorized access and limit inter-container communications.
8. Ease of Management: There are tools like Kubernetes which help in orchestrating containers. These tools have capabilities like self-healing, failover, implementation of deployment strategies, scaling, monitoring, logging, and debugging, etc.
What are the disadvantages of containers?
1. Complexity: Containerization tools, such as Docker and Kubernetes, can be complex to set up and manage, especially for organizations that are new to containerization.
2. Lack of standardization: There are many different containerization tools available, and they may have different features, capabilities, and learning curves. This can make it difficult to choose the right tool for a particular use case.
3. Limited interoperability: Different containerization tools may not work together seamlessly, making it difficult to manage a multi-cloud or hybrid environment.
It’s worth noting that different containerization tools have different strengths & weaknesses and that the cons might not be an issue depending on the specific use case. Additionally, the community is actively working on these cons through the development of new features and better integration with other technologies.
Why are organizations shifting to containers?
Before the introduction of containerization, one of the main problems developers and operations teams faced was the difficulty of consistently reproducing a particular environment. Applications often had specific dependencies and configurations that needed to be met in order to run correctly, and it was difficult to ensure that these dependencies and configurations were met consistently across different environments. This led to issues such as “works on my machine” where an application would run correctly on a developer’s machine but not on a production server. Containerization allows developers to create, build and deploy apps faster and more securely.
Additionally, it was difficult to manage and scale applications effectively. Deploying new versions of an application often required significant manual effort and scaling an application to handle increased load could be a time-consuming and error-prone process.
The use of virtual machines (VMs) as the primary method of virtualization had the problem of over-allocation of resources. Each VM had its own operating system, leading to the wastage of resources and increased storage and memory footprint.
Containerization tools were designed to address these problems by providing a consistent and isolated environment for applications to run in, making it easier to manage and scale applications, and allowing for the efficient use of resources.
When we see the above advantages for containers, we can understand why organizations are rapidly adapting containerization technologies over virtualization. Developers can convert monolith applications to loosely coupled applications which helps in resolving dependencies. Which in turn helps to make applications more secure and agile.