NuttX File System

Overview. NuttX includes an optional, scalable file system. This file-system may be omitted altogether; NuttX does not depend on the presence of any file system.

Pseudo Root File System. A simple in-memory, pseudo file system can be enabled by default. This is an in-memory file system because it does not require any storage medium or block driver support. Rather, file system contents are generated on-the-fly as referenced via standard file system operations (open, close, read, write, etc.). In this sense, the file system is pseudo file system (in the same sense that the Linux /proc file system is also referred to as a pseudo file system).

Any user supplied data or logic can be accessed via the pseudo-file system. Built in support is provided for character and block drivers in the /dev pseudo file system directory.

Mounted File Systems The simple in-memory file system can be extended my mounting block devices that provide access to true file systems backed up via some mass storage device. NuttX supports the standard mount() command that allows a block driver to be bound to a mountpoint within the pseudo file system and to a file system. At present, NuttX supports the standard VFAT and ROMFS file systems, a special, wear-leveling NuttX FLASH File System (NXFFS), as well as a Network File System client (NFS version 3, UDP).

Comparison to Linux From a programming perspective, the NuttX file system appears very similar to a Linux file system. However, there is a fundamental difference: The NuttX root file system is a pseudo file system and true file systems may be mounted in the pseudo file system. In the typical Linux installation by comparison, the Linux root file system is a true file system and pseudo file systems may be mounted in the true, root file system. The approach selected by NuttX is intended to support greater scalability from the very tiny platform to the moderate platform.