Linux File System

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The purpose of the recommended Linux file system hierarchy standard by FHS - File Hierarchy Standard

This standard recomendations enable:

• Software to predict the location of installed files and directories

• Users to predict the location of installed files and directories

This is done by:

• Specifying guiding principles for each area of the filesystem,

• Specifying the minimum files and directories required,

• Enumerating exceptions to the principles

• Enumerating specific cases where there has been historical conflict.

The FHS document can be useful to:

• Independent software suppliers to create applications which are FHS compliant, and work with

distributions which are FHS compliant

• OS creators to provide systems which are FHS compliant

• Users to understand and maintain the FHS compliance of a system

The limited scope of the FHS recommendations:

• Local placement of local files is a local issue, so FHS does not attempt to usurp system administrators.

• FHS addresses issues where file placements need to be coordinated between multiple parties such as

local sites, distributions, applications, documentation, etc...

This standard assumes that the operating system underlying an FHS-compliant file system supports the

same basic security features found in most UNIX filesystems.

It is possible to define two independent distinctions among files. In general, files that differ in either of these respects should be located in different directories. This makes it easy to store files with different usage characteristics on different file-systems:

- shareable : Files that can be stored on one host and used on others

- unshareable : files that are not shareable. For example, the files in user home directories are shareable whereas device lock

files are not

- Static : "Static" files include binaries, libraries, documentation files and other files that do not change without

system administrator intervention

- variable : "Variable" files are files that are not static

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/ - Root

/bin - Essential command binaries, that could be used by all users

Purpose

/bin contains commands that may be used by both the system administrator and by users, but which are

required when no other file-systems are mounted (e.g. in single user mode). It may also contain commands which are used indirectly by scripts.

Requirements

There must be no subdirectories in /bin.

The following commands, or symbolic links to commands, are required in /bin:

Command Description

cat Utility to concatenate files to standard output

chgrp Utility to change file group ownership

chmod Utility to change file access permissions

chown Utility to change file owner and group

cp Utility to copy files and directories

date Utility to print or set the system data and time

dd Utility to convert and copy a file

df Utility to report filesystem disk space usage

dmesg Utility to print or control the kernel message buffer

echo Utility to display a line of text

false Utility to do nothing, unsuccessfully

hostname Utility to show or set the system's host name

kill Utility to send signals to processes

ln Utility to make links between files

login Utility to begin a session on the system

ls Utility to list directory contents

mkdir Utility to make directories

mknod Utility to make block or character special files

more Utility to page through text

mount Utility to mount a filesystem

mv Utility to move/rename files

ps Utility to report process status

pwd Utility to print name of current working directory

rm Utility to remove files or directories

rmdir Utility to remove empty directories

sed The `sed' stream editor

sh POSIX compatible command shell

stty Utility to change and print terminal line settings

su Utility to change user ID

sync Utility to flush filesystem buffers

true Utility to do nothing, successfully

umount Utility to unmount file systems

uname Utility to print system information

Optionallly

csh The C shell (optional)

ed The `ed' editor (optional)

tar The tar archiving utility (optional)

cpio The cpio archiving utility (optional)

gzip The GNU compression utility (optional)

gunzip The GNU uncompression utility (optional)

zcat The GNU uncompression utility (optional)

netstat The network statistics utility (optional)

ping The ICMP network test utility (optional)

/bin/csh may be a symbolic link to /bin/tcsh or /usr/bin/tcsh.

Rationale:

The tar, gzip and cpio commands have been added to make restoration of a system possible

(provided that / is intact).

/boot (Static & Unsharable) - Static files of the boot loader

Purpose

This directory contains everything required for the boot process except configuration files not needed at

boot time and the map installer. Thus /boot stores data that is used before the kernel begins executing

user-mode programs. This may include saved master boot sectors and sector map files.

Programs necessary to arrange for the boot loader to be able to boot a file must be placed in /sbin.

Configuration files for boot loaders that are not required at boot time must be placed in /etc.

Optionally

The operating system kernel must be located in either / or /boot.

Certain architectures may have other requirements for /boot related to limitations or expectations

specific to that architecture. These requirements are not enumerated here; distributions are allowed to add

requirements as needed to enable system startup on these architectures.

/dev - Device files

Purpose

The /dev directory is the location of special or device files.

Optionally

If it is possible that devices in /dev will need to be manually created, /dev must contain a command

named MAKEDEV, which can create devices as needed. It may also contain a MAKEDEV.local for any

local devices.

If required, MAKEDEV must have provisions for creating any device that may be found on the system, not

just those that a particular distribution installs.

/etc - (Static & Unsharable) Host−specific system configuration

/lib - Essential shared libraries and kernel modules

/media - Mount point for removeable media

/mnt - Mount point for mounting a filesystem temporarily

/opt (Static & Shareable) Add−on application software packages

/run - Data relevant to running processes

/sbin - Essential system binaries

/srv - Data for services provided by this system

/tmp - Temporary files

/usr (Static & Shareable) - Secondary hierarchy

/var - Variable data

- Optionals that could be included in Root Directory:

/home - User home directories (optional)

/lib - Alternate format essential shared libraries (optional)

/root- Home directory for the root user (optional)

The Linux FileSystem Standard Hierarchy - FHS

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The Linux FileSystem Standard Hierarchy - FHS

The PURPOSE of the recommended Linux Filesystem Hierarchy Standard

This standard recomendations enable:

• Software to predict the location of installed files and directories

• Users to predict the location of installed files and directories

This is done by:

• Specifying guiding principles for each area of the filesystem,

• Specifying the minimum files and directories required,

• Enumerating exceptions to the principles

• Enumerating specific cases where there has been historical conflict.

The FHS document can be useful to:

• Independent software suppliers to create applications which are FHS compliant, and work with

distributions which are FHS compliant

• OS creators to provide systems which are FHS compliant

• Users to understand and maintain the FHS compliance of a system

The limited scope of the FHS recommendations:

• Local placement of local files is a local issue, so FHS does not attempt to usurp system administrators.

• FHS addresses issues where file placements need to be coordinated between multiple parties such as

local sites, distributions, applications, documentation, etc...