Linux uses a logical file system hierarchy standard to organize files across multiple directories and file systems. The root directory is at the top level and is represented by a forward slash. Key directories include /bin for executable commands, /lib for shared libraries, /etc for configuration files, and /var for dynamic data. Common file systems in Linux include ext2, ext3, ReiserFS, tmpfs, and proc.

2.  Linux files are organized in a logical fashion for ease of
administration.
 This logical division of files is maintained in hundreds
of directories that are located in larger containers
called file system.
 RED HAT LINUX follows the FILE SYSTEM Hierarchy
standard(FHS) for file organization.

3. FILE SYSTEM
 Disk Based:
 DISK-based file systems are created on
physical media such as a hard disk.
 Memory- Based:
 Memory- based file systems, also called virtual
file system, are created at system boot up and
destroyed at shut down.

4. FILE SYSTEM TREE
 The Linux file system structure is like an inverted tree
with the root of the tree at the top and branches and
leaves at bottom.
 The top level is referred to as root and represented by
forward slash(/) character.
 Two file systems -/ and /boot- are created, by default,
when RHEL is installed.
 The custom installation procedure provided later in this,
also creates /var, /usr,/tmp,/opt and /home file systems
in addition to / and /boot.

5. FILE SYSTEM TREE
• These directories hold Static and Dynamic(or variable)
information.
 The Static refers to file contents that are not usually modified.
 Static dir normally contain cmds, lib routines, kernel files,
devices files, etc.
 The Dynamic or variable data refers to file contents that are
modified as required.
 DD hold log files, status files, configuration files, temporary
files, etc.
 RHEL provides a graphical file manager called nautilus
that can be used to view and navigate within the directory
structure.

6. Linux Directory Hierarchy

7.  The Binary directory (/bin):
 The binary directory contains crucial user executable
commands.
 This directory holds static data files.
 The library directory (/lib):
 The library directory contains shared library files required by
programs.
 It contains sub-directories that hold static data files.
 The System Binary Directory (/sbin):
 Most commands required at system up are located in the
system binary directory.
 In addition, most cmds requiring root privileges to run are
also located here.
 The /sbin dir holds static data files.

8.  The etcetera directory(/etc):
 The etcetera directory holds most configuration files.
 The /etc dir contains dynamic data files.
 The lost+ found dir(/lost+found):
 This directory is used to hold files that become orphan after
system crash.
 An orphan file is a file that has lost its name and it holds
dynamic data.
 /root:
 This is default home directory location for the root user.
 /srv:
 This dir holds server data associated with database, website,
etc.

9.  /boot:
 It contains linux kernels, boot loader and boot configuration
files in addition to other files required to boot RHEL.
 The /boot file system contains static data files.
 /var:
 /var contains data that frequently change while the system is
up and running.
 UNIX system Resoucres file system(/usr):
 Disk based, this file system contains general files related to
the system.

10. ext2
 The ext2 or second extended filesystem is a file system
for the Linux kernel.
 It was initially designed by Rémy Card as a replacement for
the extended file system (ext).
 ext2 was the default filesystem in several Linux
distributions.
 ext2 is still the filesystem of choice for flash-based storage
media (such as SD cards, and USB flash drives), since its
lack of a journal minimizes the number of writes.

11. ext3
 ext3, or third extended filesystem, is a journaled file
system that is commonly used by the Linux kernel.
 It is the default file system for many popular Linux
distributions.
 Its main advantage over ext2 is journaling, which
improves reliability and eliminates the need to check
the file system after an unclean shutdown.
 Its successor is ext4.

12. Journaling
 A journaling is a file system that keeps track of the
changes that will be made in a journal (usually a
circular log in a dedicated area of the file system)
before committing them to the main file system.
 In the event of a system crash or power failure, such
file systems are quicker to bring back online (stable
state)and less likely to become corrupted.
 Journaling provides for fast and effective recovery in
case of disk crashes, instead of using e2fsck or fsck.

13. ReiserFS
 The Reiser file system is a journaling FS designed for
fast server performance, especially in directories
containing thousands of files.
 It is more space efficient than most other file system,
because it does not take up a minimum of one block
per file.
 If we want to write a bunch of really small files to disk,
ReiserFS squeezes them all into one block instead of
writing one small file to one block file.

15.  Cramfs: it is designed to cram a file system onto a
small flash memory device.
 It is small, simple and able to compress things well.
 The largest file sizes is 16 MB, and the largest FS size is
256MB.
 To update cramfs mkcramfs tool is used.

16.  tmpfs is a common name for a temporary file storage
facility on many Unix-like operating systems.
 It is intended to appear as a mounted file system, but
stored in volatile memory instead of a persistent
storage device.
 A similar construction is a RAM disk, which appears as
a virtual disk drive and hosts a disk file system.

17.  ramfs: It is basically cramfs without the compression.
 romfs: This is a read-only file system that is mostly used
for the initial RAM disks of installation disks.
 It was designed to take up very little space, so it can fit
a kernel and some useful code into a small boot disk.
 The romfs file system is created with a program called
genromfs.
 It is very useful as an initial ROM holding kernel
modules that can be loaded later as needed.

18.  PROC:
 proc is a virtual file system that acts as an interface to
the kernel’s internal data structures.
 proc can be used to get detailed information about a
system’s hardware and to change kernel parameters at
run time.
 Even the process listing command, ps, gets its
information from the proc file system.
 The kernel parameters can be changed with the sysctl
command.