3.2. Overview of File System Hierarchy Standard (FHS)
Red Hat is committed to the Filesystem Hierarchy
Standard (FHS), a collaborative
document that defines the names and locations of many files and
The FHS document is the authoritative reference to any FHS-compliant
file system, but the standard leaves many areas undefined or
extensible. This section is an overview of the standard and a
description of the parts of the file system not covered by the standard.
Compliance with the standard means many things, but the two most
important are compatibility with other compliant systems and the ability
to mount a /usr/ partition as read-only because it
contains common executables and should not be changed by users.
Since the /usr/ directory is mounted read-only, it
can be mounted from the CD-ROM or from another machine via a read-only
3.2.1. FHS Organization
The directories and files noted here are a small subset of those
specified by the FHS document. Refer to the latest FHS document for
the most complete information.
184.108.40.206. The /dev/ Directory
The /dev/ directory contains file system entries
which represent devices that are attached to the system. These files
are essential for the system to function properly.
220.127.116.11. The /etc/ Directory
The /etc/ directory is reserved for
configuration files that are local to the machine. No binaries are
to be put in /etc/. Any binaries that were
once located in /etc/ should be placed into
/sbin/ or possibly /bin/.
The X11/ and skel/
directories are subdirectories of the /etc/
The /etc/X11/ directory is for X11
configuration files such as XF86Config. The
/etc/skel/ directory is for "skeleton" user
files, which are used to populate a home directory when a user is
18.104.22.168. The /lib/ Directory
The /lib/ directory should contain only those
libraries that are needed to execute the binaries in
/bin/ and /sbin/. These
shared library images are particularly important for booting the
system and executing commands within the root file system.
22.214.171.124. The /mnt/ Directory
The /mnt/ directory is for temporarily mounted
file systems, such as CD-ROMs and floppy disks.
126.96.36.199. The /opt/ Directory
The /opt/ directory provides storage for large,
static application software packages.
A package placing files in the /opt/ directory
creates a directory bearing the same name as the package. This
directory in turn holds files that otherwise would be scattered
throughout the file system, giving the system administrator an easy
way to determine the role of each file within a particular package.
For example, if sample is the name of a
particular software package located within the
/opt/ directory, then all of its files could be
placed within directories inside the
/opt/sample/ directory, such as
/opt/sample/bin/ for binaries and
/opt/sample/man/ for manual pages.
Large packages that encompass many different sub-packages, each of
which accomplish a particular task, also go within the
/opt/ directory, giving that large package a
standardized way to organize itself. In this way, our
sample package may have different tools that
each go in their own sub-directories, such as
/opt/sample/tool2/, each of which can have
their own bin/, man/, and
other similar directories.
188.8.131.52. The /proc/ Directory
The /proc/ directory contains special files
that either extract information from or send information to the
Due to the great variety of data available within
/proc/ and the many ways this directory can be
used to communicate with the kernel, an entire chapter has been
devoted to the subject. For more information, please refer to Chapter 5 The proc File System.
184.108.40.206. The /sbin/ Directory
The /sbin/ directory is for executables used
only by the root user. The executables in
/sbin/ are only used to boot and mount
/usr/ and perform system recovery operations.
The FHS says:
"/sbin typically contains files essential
for booting the system in addition to the binaries in
/bin. Anything executed after
/usr is known to be mounted (when there are
no problems) should be placed in /usr/sbin.
Local-only system administration binaries should be placed into
At a minimum, the following programs should be in
The /usr/ directory is for files that can be
shared across a whole site. The /usr/ directory
usually has its own partition, and it should be mountable read-only.
At minimum, the following directories should be subdirectories of
The bin/ directory contains executables,
dict/ contains non-FHS compliant documentation
pages, etc/ contains system-wide configuration
files, games is for games,
include/ contains C header files,
kerberos/ contains binaries and much more for
Kerberos, and lib/ contains object files and
libraries that are not designed to be directly utilized by users or
shell scripts. The libexec/ directory contains
small helper programs called by other programs,
sbin/ is for system administration binaries
(those that do not belong in the /sbin/ directory),
share/ contains files that are not
architecture-specific, src/ is for source code,
and X11R6/ is for the X Window System
(XFree86 on Red Hat Linux).
220.127.116.11. The /usr/local/ Directory
The FHS says:
"The /usr/local hierarchy is for use by the
system administrator when installing software locally. It needs
to be safe from being overwritten when the system software is
updated. It may be used for programs and data that are
shareable among a group of hosts, but not found in
The /usr/local/ directory is similar in
structure to the /usr/ directory. It has the
following subdirectories, which are similar in purpose to those in
the /usr/ directory:
System log files such as messages/ and
lastlog/ go in the
/var/log/ directory. The
/var/lib/rpm/ directory also contains the RPM
system databases. Lock files go in the
usually in directories particular for the program using the file.
The /var/spool/ directory has subdirectories for
various systems that need to store data files.
3.2.2. /usr/local/ in Red Hat Linux
In Red Hat Linux, the intended use for the /usr/local/
directory is slightly different from that specified by the FHS. The
FHS says that /usr/local/ should be where
software that is to remain safe from system software upgrades is
stored. Since system upgrades from under Red Hat Linux performed safely with
the rpm command and graphical
Package Management Tool application, it is not
necessary to protect files by putting them in
/usr/local/. Instead, the
/usr/local/ directory is used for software that
is local to the machine.
For instance, if the /usr/ directory is mounted
as a read-only NFS share from a remote host, it is still possible to
install a package or program under the