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Containers 101 Part 2 - Containers Core Concepts

containers Feb 04, 2024


Welcome to the second part of our Containers 101 series. In this post, we'll delve into the core concepts of container technology, demystifying how containers work and why they've become a cornerstone in modern software development and deployment. You can read Part 1 at parts of this series are also captured in the Containers 101 YouTube video, which is available on the Trainso YouTube Channel.

Introduction to Containers

Containers offer a lightweight, efficient alternative to traditional virtual machines (VMs) for many use cases. Unlike VMs, which run a complete operating system including its own kernel, containers share the host's kernel. This makes containers more resource-efficient and faster to start. Containers encapsulate applications along with their dependencies in a portable format, managed by a container engine rather than a hypervisor. This architecture not only resolves the infamous "It works on my machine" problem but also facilitates the implementation of architectural patterns such as microservices.

Core Concepts of Containers

  • Container Images: These are immutable templates that include everything needed to run an application—code, runtime, system tools, libraries, and settings. Modifications to an image add new layers on top of existing ones, ensuring that the base image remains unchanged.
  • Containers: When a container image is run, it becomes a container. Containers are instances of images and provide the runtime environment for the encapsulated application.
  • Container Registries: These are storage and distribution systems for container images. Examples include DockerHub, a popular public registry, and cloud provider offerings like Google Container Registry (GCR), Amazon Elastic Container Registry (ECR), and Azure Container Registry (ACR).
  • Container Engines vs. Container Runtimes: Container engines, such as the Docker container engine, provide high-level management of images and containers, abstracting away the operating system. Container runtimes, on the other hand, manage the lifecycle of containers at a lower level. They handle the execution of containers by leveraging Linux kernel features but are not involved in higher-level management tasks. Popular container runtimes include runc, crun, and containerd.

Containers and Linux

Containers are deeply intertwined with Linux, relying on kernel features like namespaces for isolation and cgroups for resource allocation. While containers are typically run on Linux platforms, they can also operate on Windows and Mac through virtualization layers that provide a Linux environment. Some containers even utilize minimal Linux distributions, such as CoreOS and Fedora Atomic, to maintain a lightweight footprint.

The Importance of Container Technology

Container technology has revolutionized how applications are developed, deployed, and scaled. By abstracting the complexities of the underlying infrastructure, containers enable developers to focus on building and deploying applications more efficiently. The portability of containers simplifies the deployment process across different environments, from development to production, thereby enhancing consistency and reliability. Additionally, with the rise of Container as a Service (CaaS) offerings, organizations can automatically scale their applications in the cloud, reducing the operational overhead associated with traditional infrastructure management.


Containers provide a powerful, efficient, and consistent way to package and run applications, facilitating modern architectural patterns and enabling seamless scalability. As we continue our Containers 101 series, we'll explore more advanced topics, including container orchestration, security practices, and how to optimize container deployments for production environments. Stay tuned for more insights as we further unravel the world of container technology, empowering you to harness its full potential in your projects.

See also

Read part 3 of this series at

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