Union Filesystems

Lesson in the Docker Roadmap · Stage 2: Underlying Technologies

Last updated 14 September 2026

What is Union Filesystems?

Union filesystems (UnionFS) create virtual, layered file structures by overlaying multiple directories without modifying originals. Docker uses this to manage storage efficiently by minimizing duplication and reducing image sizes through layered filesystem approach that keeps directory contents separate while mounted together.

Study this in the interactive course See the whole Docker roadmap

Free resources to learn Union Filesystems

ArticleAUFS (Advanced Multi-Layered Unification Filesystem)
ArticleOverlayFS (Overlay Filesystem)
ArticleBtrfs (B-Tree Filesystem)
ArticleZFS (Z File System)

Union Filesystems: common questions

Can I learn Union Filesystems in Hindi?

This lesson is written in English. Once you sign in, open it in the interactive course and ask the AI tutor to explain Union Filesystems in Hindi or Hinglish. The tutor answers from this lesson’s own text, so it stays on the syllabus, and it runs on your own Google, OpenAI or Anthropic key.

Is this Union Filesystems tutorial for beginners?

It is lesson 9 of 56 in the free Docker roadmap, in stage 2, Underlying Technologies. If you are new to Docker, start from stage 1 and come back here in order; if you already know the earlier stages, this lesson stands on its own.