Chapter 14: File Systems

In Chapters 4, 5, and 13, we looked at file I/O, with a particular focus on regular (i.e., disk) files. In this and the following chapters, we go into detail on a range of file-related topics:

• This chapter looks at file systems.
• Chapter 15 describes various attributes associated with a file, including the file timestamps, ownership, and permissions.
• Chapters 16 and 17 consider two new features of Linux 2.6: extended attributes and access control lists (ACLs). Extended attributes are a method of associating arbitrary metadata with a file. ACLs are an extension of the traditional Unix file permission model.
• Chapter 18 looks at directories and links.

The majority of this chapter is concerned with file systems, which are organized collections of files and directories. We explain a range of file system concepts, sometimes using the traditional Linux ext2 file system as a specific example. We also briefly describe some of the journaling file systems available on Linux.

We conclude the chapter with a discussion of the system calls used to mount and unmount a file system, and the library functions used to obtain information about mounted file systems.

14 File Systems
14.1 Device Special Files (Devices)
14.2 Disks and Partitions
14.3 File Systems
14.4 I-nodes
14.5 The Virtual File System (VFS)
14.6 Journaling File Systems
14.7 Single Directory Hierarchy and Mount Points
14.8 Mounting and Unmounting File Systems
14.8.1 Mounting a File System: mount()
14.8.2 Unmounting a File System: umount() and umount2()
14.9 Advanced Mount Features
14.9.1 Mounting a File System at Multiple Mount Points
14.9.2 Stacking Multiple Mounts on the Same Mount Point
14.9.3 Mount Flags That Are Per-mount Options
14.9.4 Bind Mounts
14.9.5 Recursive Bind Mounts
14.10 A Virtual Memory File System: tmpfs
14.11 Obtaining Information about a File System: statvfs()
14.12 Summary
14.13 Exercises