EXT2 File System

Abstract

This chapter covers EXT2 file system. The goal of this chapter is to lead the reader to implement a complete EXT2 file system that is totally Linux compatible. The premise is that if the reader understands one file system well, it should be easy to adapt to any other file systems. It first describes the historic role of EXT2 file system in Linux and the current status of EXT3/EXT4 file systems. It uses programming examples to show the various EXT2 data structures and how to traverse the EXT2 files system tree. Then it shows how to implement an EXT2 file system which supports all file operations as in the Linux kernel. It shows how to build a base file system by mount_root from a virtual disk. Then it divides the file system implementation into 3 levels. Level-1 expands the base file system to implement the file system tree. Level-2 implements read/write operations of file contents. Level-3 implements mount/umount of file systems and file protection. In each level, it describes the algorithms of the file system functions and demonstrates their implementations by programming examples. Each level is cumulated by a programming project. The final project is to integrate all the programming examples and exercises into a fully functional file system.