LINUX DIRECTORY STRUCTURE

Presented By :-

JITU MISTRY

INTRODUCTION

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What is Directory?

It’s bunch of system files and also data files.

What is Directory in LINUX?

It’s same meaning in LINUX but in the LINUX there is

only one root.

How the LINUX Directory differ from that of familiar

Windows?

In windows every drive has it’s own root , opposite to it

, in linux only single drive and single root.

Example

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Root

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Root is ambiguous in one respect.

1. It can refer to the top of the file structure.

2. It can also be the name of the Administrator type

account in Linux.

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Difference between ‘/’ and ‘/Root’

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1. /

‘/’ is called as a root.

It’s Root directory.

Root of the all file systems of linux.

Every directory is “under” root ultimately.

2. /root

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Root is the user with God-like powers over the system. !!!

It’s administrative(root) user’s home directory.

/boot

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Contains the boot loader , Grub and linux kernel

Contains everything required for the boot process except

for configuration files not needed at boot time.

Stores data that is used before the kernel begins

executing user-mode programs.

/boot is static and unsharable directory.

If /boot is lost , then we can’t boot os .

Some command for /Boot

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/Root

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Home directory of root user.

Root is the name of system Admin.

/Root = system admin or Super User directory.

Why not in '/home'?

Because '/home' is often located on a different

partition or even on another system and would thus

be inaccessible to 'root' when - for some reason -

only '/' is mounted.

/bin

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Stands for binary

Need for system startup

Used by everyone in terminal

Shells like bash, csh

No subdirectories in /bin

Basic commands for

Navigating in filesystem

File management

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bin

bash bzip2 cat gzip ls mv rm...

/sbin

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binary files usually for system administration.

Only root can access.

System configuration programs

Format hard disk

Manage hardware

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sbin

fsck mkfs mount adduser poweroff...

/bin vs /sbin

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/bin directory contains executable programs which

are needed in single user mode and to bring the

system up or repair it.

/sbin Like /bin, holds commands needed to boot the

sys-tem, but which are usually not executed by normal

users.

/opt

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“optional” software

/opt/bin, /opt/doc, /opt/include, /opt/info,

/opt/lib, and /opt/man

installed under either /opt/ or /opt/ sub-

directory.

/srv

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srv stands for service.

site-specific data

Contains server specific services related data.

For example, /srv/cvs contains CVS related

data.

/tmp

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Contains file that are required temporarily

Directory is cleared out at boot or at shutdown.

/lib

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All essential libraries which are needed for

system startup

Windows equivalent to a shared library would

be a DLL (dynamically linked library) file

Also in this directory are kernel modules

/lib (conti..)

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Other library locations for other programs include

/usr/lib and /usr/local/lib

Generally these correspond to where the binary is

installed, i.e. a binary in /usr/bin would put a library

in /usr/lib, and a binary in /usr/local/bin would put

a library in usr/local/lib

/dev

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• Stands for devices.

• Linux filesystem : everything is a file or a directory.

• So device is treated as file. Usually It is the location

of device files

• C:\Windows\System in Windows Contains a file describing every device,and these files can send data to each device.

• It is equivalent to a mashup of the Device Manager.

• A device and a file both can be read from and written to. So config a device is same with edit a file.

/dev

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EX: sending data to /dev/ttyS0 that means you are

sending data to a communication device, such as a

modem.

/dev/dsp : speaker device

/dev/dsp is speaker configuration file means it is for

sound card.

cat /etc/lilo.conf > /dev/dsp

The sound you will hear is the sound of

your /etc/lilo.conf file

/dev

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●/dev/ttyS0

●/dev/psaux

●/dev/lp0

●/dev/dsp

●/dev/usb

●/dev/sda

●/dev/scd

●/dev/cdrom

●/dev/fd0

●/dev/had

→Device connected to Com1 (Modem, mouse,..)

→PS/2 mouse connection

→First parallel port

→Sound card (digital signal processor)

→USB device nodes.

→First SCSI device

→First SCSI CD-ROM device

→CD-ROM drive

→floppy drive

→The partition on primary hdd

/etc

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• Contains all system related configuration files.

• Those files must be static and cannot be an executable binary.

• These files are generally text files andcan be edited using any

text editor:emacs or vi on the command line, or whatever

graphical equivalent (e.g. gedit, kate) your desktop offers.

• /etc/rc.d directory contains the system startup scripts.

/etc

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• Fstab : Static information about filesystems.

• Group : User group file.

• Passwd : This is the password file, but it contains more: user

name, user password, userID, group ID, home directory, and

shell. It can optionally contain the user's “real name”.

• /etc/sgml : Configuration files for SGML

• /etc/xml : Configuration files for XML

• /etc/hostname : Contains the hostname of your machine

• /etc/hosts : This file is used to define a system name and

domain combination with a specific IP address

/etc

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• /etc/inittab:

• /etc/fstab: system what drive to access, and where

to mount it in your System.

• /etc/x11: Configuration directory for x11, which is

the display system for graphical interfaces in Linux.

• /etc/x11/xorg.conf : specify the resolutions your

monitor and graphics card can display, for instance.

/home

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• Linux is a multi-user environment so each user is also

assigned a specific directory which is accessible only

to them and the system administrator.

• containing saved files, personal settings, etc. Contains

the user’s personal configuration files and their name

start with “.” (hidden file).

• Quite large to be used as User’s Documents Space

/mnt

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Mounting is the process by which you make a

filesystem available to the system.

On older Linux systems, the /mnt directory contains

mount.

points for removable devices that have been mounted

manually.

Mount point for temporary mounted file system.

/media

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On modern Linux systems the /media directory will

contain the mount points for removable media such as,

-USB drives,

-CD-ROMs, etc.

that are mounted automatically at insertion.

/proc

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Pseudo file system residing in the virtual memory.It is

virtual file system maintained by the Linux kernel. The

“files” it contains are peepholes into the kernel itself.

The files are readable and will give you a picture of

how the kernel sees your computer.

Maintains highly dynamic data on the state of your

operating system.

A new /proc file system is created every time your

Linux machine reboots.

/usr

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/usr is the second major section of the

filesystem.

/usr is shareable, read-only data.

Any information that is host-specific or varies

with time is stored elsewhere.

Large software packages must not use a direct

subdirectory under the /usr hierarchy.

Requirements of /usr

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bin -----Most user commands

include -----Header files included by C

programs

lib -----Libraries

local -----Local hierarchy (empty

after main installation)

sbin -----Non-vital system binaries

share -----Architecture-independent

data

/usr/bin

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Contains executable files for many Linux

commands

These are commands that are not part of the

core Linux operating system

Examples of commands in here:

- Perl

- Python

/usr/include

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General use include files, including header files,

for

C and C++ programming languages.

/usr/lib

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Contains libraries for the C and C++

programming languages

Object files, libraries, and internal files not

intended to be executed directly by users or

shell scripts

/usr/local

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The /usr/local hierarchy is for use by the system

administrator when installing software locally.

It may be used for programs and data that are

shareable amongst a group of hosts, but not

found in /usr.

Locally installed software must be placed within

/usr/local rather than /usr unless it is being

installed to replace or upgrade software in /usr.

Requirements of /usr/local

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s bin -----Local binaries

etc -----Host-specific system configuration for local binaries

games -----Local game binaries

include -----Local C header files

lib -----Local libraries

man -----Local online manuals

sbin -----Local system binaries

share -----Local architecture-independent hierarchy

src -----Local source code

/usr/sbin

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This directory contains any non-essential

binaries used exclusively by the system

administrator.

System administration programs that are

required for system repair, system recovery,

mounting /usr, or other essential functions must

be placed in /sbin instead.

/usr/share

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/usr/share is for read-only architecture independent data

files

Intended to be shared across platforms (e.g. i386,

Alpha, PPC)

Any program or package which contains or requires data

that doesn’t need to be modified should store

If the contents are variable, go to /var e.g. a game file in

/usr/share/games must be static. Game play

logs go in /var/games

Requirements of /usr/share

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man -----Online manuals

misc -----Miscellaneous architecture-

independent data

/usr/src

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Source code is placed here, for reference

purposes only.

This includes the source code for the Linux

kernel.

/var

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• This is files that are expected to be updated and

changed.

• This includes:

Administrative and Logging data

Temporary files

Websites

Mail directories

Print spool

/var Sharing

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Not Shareable:

/var/log, /var/lock, and /var/run.

Shareable:

/var/mail, /var/cache/man, /var/cache/fonts, and

/var/spool/news.

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Because there might be circumstances when you may

want to mount /usr as read-only,

e.g. if it is on a CD or on another computer.

However, /var must not be linked to /usr because this

makes separation of /usr and /var more difficult and

is likely to create a naming conflict. Instead, link /var

to /usr/var

Why not put it into /usr ?

var

cache lib lock log www named

message boot.log

Backups

Subdirectory of /var

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Directory Description

cache Application cache data

lib Variable state information

local Variable data for /usr/local

lock Lock files

log Log files and directories

opt Variable data for /opt

run Data relevant to running processes

spool Application spool data

tmp Temporary files preserved between

system reboots

Carsh for the dumped data

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‘Reserved’ Directory

They must not be used arbitrarily by some new

application,

since they would conflict with historical and/or local

practice. They are

/var/backups

/var/msgs

/var/preserve

Permissions in FS

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There are 3 basic permissions

Read (r)

Write (w)

Execute (x)

There are 3 basic level of users

Owner

Groups

Others

How to find the permissions:

ls -l

Mehod for Permission

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(1) Octal method

Eg: chmod 444 hello.txt

(2) Alphabets

chmod [a/u/g/o +/- r/w/x]

<filename>

Eg: chmod ugo+r-wx hello.txt

(3) Reference

Eg: chmod –reference=hello.txt testfile.txt

Adv. Softlink in Linux FS

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If Root FS become 100% full, we have to create one

soft link that would point to another point mount

created with on same disk ultimately that New

Fs(/test) will store data instead of root

Symbolic links, or "symlinks" work a little like

Windows shortcuts

Symbolic links work on the files and directory

Adv. Hard link in Linux FS

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There are basically two main limitations with hard

links:

- Hard links normally require that the link and the file

reside in the same file system.

- Only the super user can create a hard link to a

directory.

Thus, symbolic links were introduced to get around the

limitations of hard links.

So, the question is, are hard links still needed?

Are Hard links still needed?

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Symlinks aren't followed by some HTTP servers

Hard-Links can be used for backups

You can delete any version of a hard link without

affecting the others.

Hard links allow us to take one file and have it be

multiple places in the file system at once, which save

lots of memory.

Thank you

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