How Samba interacts/works with File Systems through VFS?
Samba interacts with file systems internally through its Virtual File System (VFS) layer.
This VFS layer makes it easier for Samba to work with different types of file systems by hiding their specific details. It gives Samba a uniform way to handle things like opening, reading, writing, and closing files, no matter what kind of file system it's dealing with.
Let's understand in detail how VFS, Samba and different file systems work together:
When a client (such as a computer running Windows, macOS, or Linux operating system) wants to access files shared by Samba from a server, client first establishes a connection with the Samba server over the network using the SMB/CIFS (Server Message Block / Common Internet File System) protocol, which is a set of rules governing how data is transmitted and how clients interact with servers in a file sharing environment connected through network.
Samba then parses the incoming SMB/CIFS requests from the client to understand the client's file access intentions. These requests could include operations like opening files, reading or writing data, creating directories, listing directory contents, and more.
Samba's VFS layer plays a main role at this stage! Instead of directly interacting with the underlying file system, Samba passes these file system requests through its VFS layer. The VFS layer provides a set of abstract functions for performing file operations, such as open, read, write, close, mkdir, rmdir, etc.
It is worthwhile to note that Samba's VFS layer can be easily extended to handle different file system operations in different desired ways.
Example: vfs_ceph, vfs_gluster, vfs_gpfs, vfs_btrfs
Once the file system requests pass through the VFS layer, they are translated into actual file system operations appropriate for the underlying filesystem. For example, if Samba is working with CephFS, the requests are translated to be appropriate for Ceph file system. This is done using libcephfs. We can explore the source code here After performing the necessary file system operations, Samba recieves an appropriate response from the server i.e from the underlying file system in the server to send back to the client.
Samba then sends the response back to the client over the network using the SMB/CIFS protocol.
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