Chapter 1 Filesystem Structure; Why Share A Common Structure; Overview Of Filesystem Hierarchy Standard (Fhs) - Red Hat LINUX 7.2 Reference Manual

Section 1.2:Overview of Filesystem Hierarchy Standard (FHS)
1 Filesystem Structure

1.1 Why Share a Common Structure?

An operating system's filesystem structure is its most basic level of organization. Almost all of the
ways an operating system interacts with its users, applications, and security model are dependent upon
the way it stores its files on a primary storage device (normally a hard disk drive). It is crucial for a
variety of reasons that users, as well as programs at the time of installation and beyond, be able to
refer to a common guideline to know where to read and write their binary, configuration, log, and
other necessary files.
A filesystem can be seen in terms of two different logical categories of files:
• Shareable vs. unshareable files
• Variable vs. static files
Shareable files are those that can be accessed by various hosts; unshareable files are not available
to any other hosts. Variable files can change at any time without system administrator intervention
(whether active or passive); static files, such as documentation and binaries, do not change without an
action from the system administrator or an agent that the system administrator has placed in motion
to accomplish that task.
The reason for looking at files in this way has to do with the type of permissions given to the directory
that holds them. The way in which the operating system and its users need to utilize the files deter-
mines the directory where those files should be placed, whether the directory is mounted read-only or
read-write, and the level of access allowed on each file. The top level of this organization is crucial,
as the access to the underlying directories can be restricted or security problems may manifest them-
selves if the top level is left disorganized or without a widely-utilized structure.
However, simply having a structure does not mean very much unless it is a standard. Competing
structures can actually cause more problems than they fix. Because of this, Red Hat has chosen the
the most widely-used filesystem structure and extended it only slightly to accommodate special files
used within Red Hat Linux.

1.2 Overview of Filesystem 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 directories. We will continue to track and follow
the standard to keep Red Hat Linux FHS-compliant.
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