As can be seen from the figure above, the underlying file functions we often operate call the underlying kernel functions to manage different underlying file systems through VFS virtual file system, so we don't need to know what the file systems we operate are.

Virtual file system is a software layer in Linux kernel. It abstracts the file system internally, allows different file systems to coexist, and provides a unified file system interface for external applications.

In order to support different file systems, VFS defines basic and abstract interfaces and data structures that all file systems support.

The actual file system implements the abstract interface and data structure defined by VFS, keeps its own concepts such as file and directory consistent with the definition of VFS in form, and hides the specific implementation details under the unified interface and data structure.