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Container filesystem

The container filesystem, used for every Docker image, is represented as a list of read-only layers stacked on top of each other. These layers eventually form a base root filesystem for a container. In order to make it happen, different storage drivers are being used. All the changes to the filesystem of a running container are done to the top level image layer of a container. This layer is called a Container layer. What it basically means is that several containers may share access to the same underlying level of a Docker image, but write the changes locally and uniquely to each other. This process is shown in the following diagram:

Docker layers