/        The root directory, the top-level directory in the FHS. All other directories are subdirectories of root, which is always mounted on some partition. All directories that are not mounted on a separate partition are included in the root directory’s partition.

/bin   Essential command line utilities. Should not be mounted separately; otherwise, it could be difficult to get to these utilities when using a rescue disk.

/boot Includes Linux startup files, including the Linux kernel. Can be small; 16MB is usually adequate for a typical modular kernel. If you use multiple kernels, such as for testing a kernel upgrade, increase the size of this partition accordingly.

/etc   Most basic configuration files.

/dev  Hardware and software device drivers for everything from floppy drives to terminals. Do not mount this directory on a separate partition.

/home         Home directories for almost every user.

/lib    Program libraries for the kernel and various command line utilities. Do not mount this directory on a separate partition.

/mnt The mount point for removable media, including floppy drives, CD-ROMs, and Zip disks.

/opt   Applications such as WordPerfect or StarOffice.

/proc Currently running kernel-related processes, including device assignments such as IRQ ports, I/O addresses, and DMA channels.

/root The home directory of the root user.

/sbin System administration commands. Don't mount this directory separately.

/tmp Temporary files. By default, Red Hat Linux deletes all files in this directory periodically.

/usr   Small programs accessible to all users. Includes many system administration commands and utilities.

/var   Variable data, including log files and printer spools.