Chapter Summary

Filesystems hold directories of files. These structures store user data and system data that are the basis of users' work on the system and the system's existence. Linux supports many types of files including ordinary files, directories, links, and special files. Special files provide access to operating system features. The kernel uses major and minor device numbers to identify classes of devices and specific devices within each class. Character and block devices represent I/O devices such as hard disks and printers. Inodes, which are identified by inode numbers, are stored on disk and define a file's existence.

When the system comes up, the /etc/fstab file controls which filesystems are mounted and how they are mounted (readonly, read write, and so on). After a system crash, filesystems are automatically verified and repaired if necessary by fsck. You can use tune2fs to force the system to run fsck on a filesystem periodically when the system boots.