What is Containerization?

Containerization enables developers to create and deploy applications more efficiently and securely. Traditional methods often lead to bugs and errors when transferring code between different environments, such as from a desktop to a virtual machine or between operating systems like Linux and Windows. Containerization addresses this issue by packaging the application code, configuration files, libraries, and dependencies into a single, self-contained unit called a container. This container operates independently of the host operating system, making it portable and able to run on any platform or cloud environment without issues.

While containerization and process isolation have existed for decades, the introduction of Docker in 2013 significantly accelerated their adoption. Docker’s open-source platform provided simple developer tools and a universal packaging method, establishing an industry standard for containers. Today, organizations use containerization extensively to develop new applications and modernize existing ones for the cloud, improving their agility and operational efficiency.

According to the 2023 CNCF annual survey, over 90% of organizations are either using containers or actively evaluating them. Additionally, more than 90% of organizations that focus heavily on cloud-native app development and deployment rely on containers for their operations.

This article will explain how containerization works, discuss its benefits, and touch on its applications across different industries.

What is containerization?

Containerization is a technology that enables developers to package applications and their dependencies into a single, executable unit. This unit, known as a container, includes all necessary files, libraries, configurations, and binaries, allowing the application to run consistently across different environments.

Containers operate in isolated environments but rely on the host OS kernel, with containerization platforms like Docker mediating between the application and the OS kernel. This approach ensures that applications run seamlessly, regardless of the underlying infrastructure.

Advantages of containerization

Developers use containerization to build and deploy modern applications because of the following advantages.

1. Abstraction of the host system away from the containerized application

Containers are meant to be completely standardized. This means the container connects to the host and anything outside the container using defined interfaces. A containerized application should not rely on or be concerned with details about the underlying host’s resources or architecture over multiple operating systems. This simplifies development assumptions about the operating environment. Likewise, to the host, every container is a black box. It does not care about the details of the application inside.

2. Easy scalability

One of the benefits of containerization is that scaling can be simple given the correct application design. Service-oriented design and containerized applications provide the groundwork for easy scalability.

A developer may run a few containers on their workstation, while this system may be scaled horizontally in a staging or testing area. When the containers go into production, they can scale out again.

3. Simple dependency management and application versioning

Containers allow a developer to bundle an application or an application component along with all of its dependencies as a unit. The host system does not have to be concerned with the dependencies needed to run a specific application. As long as it can run Docker, it should be able to run all Docker containers.

This makes dependency management easy and simplifies application version management. Host systems and operations teams are no longer responsible for managing an application’s dependency needs because, apart from reliance on related containers, they should all be contained within the container itself.

4. Enhanced fault tolerance

Containers enable the development of fault-tolerant applications by running multiple microservices independently. In the event of a failure, the issue is confined to the affected container, preventing it from impacting other containers. This isolation boosts the overall resilience and availability of the application.

5. Improved security

Containerization improves security by isolating applications and preventing malicious code within one container from affecting others or the host system. Security permissions can be configured to restrict access, block unauthorized components, and limit container communication. This isolation also facilitates safe feature sharing with external teams without exposing sensitive information.

6. Efficient resource utilization through shared layering

Containers are built-in layers, allowing them to share common base layers without duplication. This layer-sharing mechanism reduces disk space usage, as multiple containers can leverage the same underlying layers.

7. Consistency and predictability

Developers can use Docker files to define the precise steps to create a container image. This approach allows the execution environment to be treated as code, enabling it to be version-controlled. Building the same Docker file in the same environment will consistently produce an identical container image, ensuring predictable and repeatable deployments.

How does containerization work?

Containers are executable software packages that run on a host OS, with a single host supporting numerous containers simultaneously. This is possible because containers run minimal, resource-isolated processes that are inaccessible to each other.

Imagine containerized applications as layers of a multi-tier system:

• The base layer is the hardware, including CPU, storage, and network interfaces.

• Above this hardware layer sits the host OS and its kernel, which mediates between the software and hardware.

• Next is the container engine, specific to the containerization technology, running on the host OS.

• At the top are the containers containing the necessary binaries, libraries, and applications, each operating in its isolated user space.

Containerization evolved from Linux groups, which isolate and control resource usage, and Linux containers (LXC), which provide namespace isolation. LXC containers include application-specific binaries and libraries but do not package the OS kernel, making them lightweight and capable of running in large numbers on limited hardware.

Docker, built on LXC, popularized container management and contributed to the Open Container Initiative (OCI) specifications, which standardized container image formats and runtimes. This standardization ensures a consistent experience across different computing environments, supporting cross-platform compatibility essential for modern digital workspaces.

Containerization vs. virtualization

Both virtualization and containerization enhance IT resource management but function at different levels and serve distinct purposes. Understanding these differences is key to choosing the right solution.

Virtualization operates at the hardware level. A hypervisor creates virtual machines (VMs) on a physical server, each VM containing a complete operating system, applications, libraries, and hardware stack. This allows multiple diverse operating systems to run on a single physical machine.

Containerization, however, works at the OS level. Containers share the host OS kernel and package only the application and its dependencies, making them much more lightweight and faster to start than VMs. Often, VMs host containerization software, enabling multiple containers to run within a single VM, combining the benefits of both technologies for scalable and manageable solutions.

Containers vs virtual machines

Containers differ from virtual machines in isolating individual applications instead of replicating an entire computer system. They are more lightweight and resource-efficient. As a result, more containers can operate on a single physical hardware unit compared to virtual machines of similar application complexity.

In contrast, virtual machines can support multiple applications simultaneously. A key distinction is that containers share a single kernel on a physical machine, whereas each virtual machine includes its kernel.

Key components in containerization

Understanding containerization involves recognizing several key components that form its architecture:

1. Container image

This is the foundational unit in containerization. It’s a lightweight, self-contained package with application code, necessary dependencies (like libraries and binaries), and a minimal operating system layer. This standardization ensures the application runs consistently across various environments.

2. Container registry

The container registry stores and manages container images as a centralized repository. Developers can upload their built images to the registry, and other systems can pull them for deployment. Common registries include Docker Hub, Amazon ECR, and Azure Container Registry.

3. Container runtime engine

This software, often called a container engine, handles the lifecycle management of containers. It takes a container image, creates a running instance, and allocates the necessary resources for execution. Docker Engine and Containerd are well-known container runtime engines.

4. Container orchestrator

Unlike container engines that manage single containers, orchestrators like Kubernetes oversee clusters of containers. They automate deployment, scaling, and networking tasks, ensuring efficient resource use and high availability for containerized applications.

5. Networking

Effective communication within containerized applications and with external services requires robust networking solutions. Docker overlay networks and Kubernetes CNI plugins enable flexible and secure network configurations.

6. Storage solutions

Data persistence is critical in containerized environments. While containers are ephemeral by default, integrating storage solutions with container orchestration platforms allows for managing data volumes and ensuring data continuity across container lifecycles.

Use cases in containerization

Containers are widely utilized in cloud computing for their lightweight, portable, and manageable nature. Here are several prominent use cases for container architecture:

1. Microservices deployment

Containers are ideal for implementing microservices architecture. They provide isolated environments for each service, enabling independent scaling, deployment, and management. This approach enhances agility and simplifies the deployment process.

2. CI/CD pipeline optimization

Containers improve Continuous Integration and Continuous Deployment (CI/CD) by creating consistent environments across development, testing, and production stages. This consistency reduces environment-specific issues and accelerates deployment cycles.

3. Application modernization

Containers facilitate the modernization of legacy applications by making them easier to deploy and manage in cloud-native environments. They also support the gradual adoption of microservices and serverless architectures.

4. Development and testing environments

Containers enable the creation of reproducible development and testing environments that mirror production settings. This ensures consistency in configuration, libraries, and dependencies, minimizing environment-related challenges.

5. Edge computing deployment

Containers can be deployed on edge devices like IoT or servers to run applications closer to the data source. This reduces latency, enhances performance and supports real-time processing for IoT and edge computing applications.

6. Batch and data processing

Containers are effective for running batch and data processing workloads, allowing horizontal scaling based on demand. This capability supports efficiently executing large-scale data tasks, such as data transformation and machine learning training.

7. Platform-as-a-Service (PaaS) solutions

Containers underpin many PaaS offerings, enabling developers to build, deploy, and manage applications without dealing with underlying infrastructure complexities. This abstraction simplifies application development and accelerates time-to-market.

Leverage DigitalOcean Managed Kubernetes for effective container management

DigitalOcean Kubernetes (DOKS) offers a developer-friendly managed Kubernetes service designed to help startups, ISVs, and digital businesses efficiently build, scale, and optimize workloads.

• Simplified operations with a managed control plane. DOKS manages the Kubernetes control plane, enabling you to focus on your applications and business logic. DigitalOcean ensures continuous monitoring, maintenance, and uptime, providing a high-availability control plane at $40 to minimize downtime. The DigitalOcean API, CLI, and UI streamline infrastructure automation and software delivery without complex Kubernetes configurations.

• Maximize uptime. DOKS enhances application availability with advanced high availability, fault tolerance, and traffic management features. It offers a 99.95% uptime SLA for the high-availability control plane, ensuring reliable operations. DigitalOcean Load Balancers distribute traffic efficiently across your infrastructure, ensuring optimal application availability and a high-quality user experience.

• Accelerate innovation with auto-scaling. The DigitalOcean Cluster Autoscaler allows startups to auto-scale clusters based on demand. SnapShooter disaster recovery is available for backups, allowing you to concentrate on developing innovative applications.

• Efficient image management with Container Registry. DigitalOcean Container Registry (DOCR) provides secure, private storage for container images and integrates seamlessly with Kubernetes and Docker. This ensures efficient image management, allowing you to store and manage container images effectively within your infrastructure.

• Cost optimization with usage-based pricing. DigitalOcean Kubernetes helps manage costs with no charge for internal traffic between Droplets. Its transparent usage-based pricing model ensures you pay only for the resources you use, avoiding the pitfalls of fixed-cost alternatives.

Effectively managing containerized applications requires robust tools, and DigitalOcean offers a comprehensive suite designed to streamline development workflows and enhance scalability, security, and performance.

Sign up for DigitalOcean today.