DevOps Articles

Deep Dive into Docker Internals — Union Filesystem

Behind this simple interface hides a lot of cool technologies and in this article we will explore one of them - the union filesystem - the underlying filesystem behind all the container and image layers...

Example of this would be bunch of users’ /home directories from remote NFS servers all unioned into single directory or merging split ISO image into single complete one.

In the previous section we mentioned some reason why this type of a filesystem might be useful, but why is it a good choice for Docker and containers in general?

We talked a bunch about how union mount works in general, but how does it all relate to Docker and its containers?

And this is really what the whole OverlayFS in Docker boils down to — a single mount command across many stacked layers.