LPI Linux Certification in a Nutshell, 2nd Edition

Objective 3: Control Filesystem Mounting and Unmounting

As discussed in See Objective 1: Create Partitions and Filesystems.," the Linux directory hierarchy is usually made up of multiple partitions, each joined to the root filesystem. Filesystems on removable media, such as CD-ROMs, Zip disks, and floppy disks, are joined in the same way, but usually on a temporary basis. Each of these separate filesystems is mounted to the parent filesystem as a directory (or mount point) in the unified hierarchy.

Directories intended as mount points usually don't contain files or other directories. Instead, they're just empty directories created solely to mount a filesystem. If a directory that already contains files is used as a mount point, its files are obscured and unavailable until the filesystem is unmounted. Typical mount points include the directories /usr, /home, /var, and others.

Managing the Filesystem Table

Since the Linux filesystem hierarchy is spread across separate partitions and/or multiple drives, it is necessary to automatically mount those filesystems at boot time. In addition, removable media and filesystems on remote NFS servers may be used regularly with recurring mount properties. All of this information is recorded in the /etc/fstab file. Filesystems defined in this file are checked and mounted when the system boots. Entries in this file are consulted for default information when users wish to mount removable media.

The /etc/fstab file (see Example 6-1) is plain text ...