# How to Build a Docker-like Container From Scratch Explore the working principles of container filesystems. - **Source:** [programming](https://brifing.si/source/21f413d8-a401-41ca-83b1-904b87bb8257) - **Published:** 2026-07-22 - **Topic:** [Software & Engineering](https://brifing.si/c/engineering) - **Original article:** - **On Brifing:** https://brifing.si/s/405081be-3d82-4cb9-93cb-b98f4d082368 ## Introduction to Container Technology Containers are lightweight virtualization solutions used to run applications in isolated environments. Tools like Docker popularized this technology. In this article, we'll learn how the filesystem, one of the core components of a container, actually works. ## Filesystem Layers Container filesystems have a layered structure. Each layer builds upon the previous one and is read-only. The top writable layer holds changes made while the container runs. This architecture ensures resource efficiency and enables image sharing. ## Union File System Concept Union File System (UnionFS) presents multiple filesystems as a single unified view. Modern implementations like OverlayFS and AUFS allow containers to merge different layers. This makes images lightweight and shareable across environments. ## Using Namespaces and Chroot Linux namespaces enable containers to have an isolated filesystem view. The chroot command temporarily changes the root directory to create a virtual environment. When combined, these techniques provide strong isolation for containerized applications. ## Building a Container from Scratch To create a basic container, first establish a filesystem hierarchy. Then implement isolation using namespaces and chroot. Finally, build the layered structure with UnionFS. These steps are ideal for understanding the mechanisms powering Docker in the background. ## The Importance of Container Technology Containers revolutionized modern software development and deployment processes. They've become indispensable due to their resource efficiency, portability, and consistent environments. Understanding their core principles enables more effective use of this transformative technology. ## Sources covering this story - https://www.reddit.com/r/programming/comments/1v3rmzu/how_container_filesystem_works_building_a/ — --- _Summary written by Brifing from the original reporting. Copyright in the original article belongs to its publisher; read the full piece at the link above._