Linux directory structure by jitu mistry

in this ppt there are talkin about the Linux directory structure. special focus on the why we have such type of directory and that is explain slide by slide

1. LINUX DIRECTORY STRUCTURE

Presented By :-
 JITU MISTRY

2. 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.

3. Example
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4. 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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6. 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.

7. 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.

8. /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 .

9. Some command for /Boot
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10. /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.

11. /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

12. 7/19/2013
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bash bzip2 cat gzip ls mv rm...

13. /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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fsck mkfs mount adduser poweroff...

15. /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.

16. /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.

17. /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.

18. /tmp
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Contains file that are required temporarily

Directory is cleared out at boot or at shutdown.

19. /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

20. /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

21. /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.

22. /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

23. /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

24. /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.

25. /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

26. /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.

27. /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

28. /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.

29. /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.

30. /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.

31. /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.

32. 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

33. /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

34. /usr/include
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General use include files, including header files,
for
C and C++ programming languages.

35. /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

36. /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.

37. 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

38. /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.

39. /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

40. Requirements of /usr/share
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man -----Online manuals

misc -----Miscellaneous architecture-
independent data

41. /usr/src
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Source code is placed here, for reference
purposes only.

This includes the source code for the Linux
kernel.

42. /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

43. /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 ?

45. var
cache lib lock logwwwnamed
message boot.log Backups

46. 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

48. 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

49. 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

50. 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

51. 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?

52. 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.

53. Thank you
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?