Chapter 9. File Systems

In this chapter

• Linux File System Concepts page 214

• ext2 page 216

• ext3 page 221

• ReiserFS page 224

• JFFS2 page 225

• cramfs page 228

• Network File System page 230

• Pseudo File Systems page 234

• Other File Systems page 240

• Building a Simple File System page 242

• Chapter Summary page 243

Perhaps one of the most important decisions an embedded developer makes is which file system(s) to deploy. Some file systems optimize for performance, whereas others optimize for size. Still others optimize for data recovery after device or power failure. This chapter introduces the major file systems in use on Linux systems and examines the characteristics of each as they apply to embedded designs. It is not the intent of this chapter to examine the internal technical details of each file system. Instead, this chapter examines the operational characteristics and development issues related to each file system presented. References in Section 9.11.1, "Suggestions for Additional Reading," are provided at the end of the chapter for the interested reader.

Starting with the most popular file system in use on earlier Linux desktop distributions, we introduce concepts using the Second Extended File System (ext2) to lay some foundation for further discussion. Next we look at its successor, the Third Extended File System (ext3), which is the default file system for many popular desktop Linux distributions being shipped today.

After introducing some fundamentals, we examine a variety of specialized file systems, including those optimized for data recovery and for storage space, and those designed for use on Flash memory devices. The Network File System (NFS) is presented, followed by a discussion of the more important Pseudo File Systems, including the proc file system and sysfs.