3. What is file system ?
> Method of storing and organizing computer files
and their data.
> Essentially, it organizes these files into a
database for the storage, organization,
manipulation, and retrieval by the computer's
operating system.
Eg:- fat, ntfs, ext4, ext3.......
4. What is file system hierarchy ?
To put it simply, it can be visualized as
a tree with its roots and all.
At the top of the hierarchy is invariably
the root path which is represented by '/' and all other directories
are created beneaththis root path in linux.
6. Root !!
In Windows, every drive has its own root C:
is the root of the C drive
In Linux, there is only one root, no matter
how many drives you may have
– In Linux, / is the root
Root is ambiguous in one respect, since it can
refer to the top of the file structure, and is
also the name of the Administrator type
account in Linux.
7. Attention
Windows uses a backslash for everything
Linux uses a forward slash for everything
In Windows, the logical drive (e.g. C:) is an
important part of the directory structure
In Linux, logical drives don't mean much. You can
even mount a separate
physical drive under a directory that is on another
drive.
In Windows, case does not matter
In Linux, everything is case sensitive.
8. Drives vs. directories
In Windows, drives are directories
In Linux, you can have several drives
all under one overall directory
9. Standard?
Distros can vary, but so can programs
When you install a program, it may not follow
the FHS in deciding where to place its files
10. /
This is the symbol for the root of the file
system in Linux
Every directory is “under” root, ultimately
This is not the same as the user “root”, which
is the user with God-like powers over the
system
The user “root” does have a directory, called /
root
13. /bin
Contains many of the commands used on the
command line
Examples include cat, chmod,dmesg, kill, ls,
mkdir more, ps, pwd, sed, su
the above commands, and many others,
must be in /bin to meet the standard.
Other commands can be optionally included,
such as tar. gzip, netstat, and ping
14. /boot
Contains files needed for boot
– kernel
– Grub menu (good to know if you are
dualbooting)
– Lilo boot sector backups
Contains data that is used before the kernel
starts executing user-mode programs
15. /dev
Kinda-sorta an equivalent to a mashup of the
Device Manager and C:WindowsSystem in
Windows
Contains a file describing every device, and
these files can send data to each device
In Linux, everything is a file or a directory
16. /dev 2
hda1, hda2, etc. are partitions on the first
physical IDE drive
sda1, sda2, etc. are partitions on the first
physical SATA drive
/dev/cdrom is the optical drive
/dev/fd0 is the floppy drive, if you have one
/dev/dsp is the speaker device
17. /etc
Perhaps the most important to understand
No binaries can be here, per the standard
This is just for configuration files
Examples include /etc/inittab, /etc/fstab ,
/etc/passwd , /etc/hosts, /etc/x11, and /etc/opt
18. /etc 2
These files are generally text files and can be
edited using any text editor:emacs or vi on
the command line, or whatever graphical
equivalent (e.g. gedit, kate) your desktop
offers
19. /etc/inittab
Describes what takes place at bootup Includes
the runlevel of the system, and which
processes should be run at each runlevel
Linux has seven runlevels, from 0-6
20. /etc/fstab
Automatically mounts file systems across
multiple drives or partitions, or even from
remote systems
This file tells the system what drive to access,
and where to mount it in your system
21. /etc/fstab
Automatically mounts file systems across
multiple drives or partitions, or even from
remote systems
This file tells the system what drive to access,
and where to mount it in your system
22. /etc/hosts
This is the famous hosts file, which matches
up names with IP addresses
This is like level 1 DNS. The system looks here
first.
This can be used to block sites by putting
their URL in here
23. /etc/passwd
This is the password file, but it contains more:
user name, user password, user ID, group ID,
home directory, and shell.
It can optionally contain the user's “real
name”
Each user is on its own line
Each user can select the shell they want to
use (most use bash these days)
24. /etc/opt/
This is a directory for the configuration files
for each system application you install.
Each application gets its own subdirectory
under /etc/opt/
25. /etc/x11
Configuration directory for x11, which is the
display system for graphical interfaces in
Linux
This can vary with different distros, so again
you need to check
/etc/x11/xorg.conf is the configuration file
that lets you specify the resolutions your
monitor and graphics card can display, for
instance
26. /home
This is where the home directories for all of
the “ordinary” users are located.
The exception is root, which has its own home
directory, /root/
Each user gets a directory with their user
name: e.g. /home/devmix
This can contain configuration files for
applications that are user-specific
27. /home Partition?
Your home directory is where you
would place all of your documents, videos,
MP3s, etc.
It can get fairly large
It is also the stuff you want to back up, and
you don't want to lose
Putting it on its own partition, or even its own
physical drive, is not a bad idea
28. Reinstalling
If you have a separate /home partition, you
can reinstall (or do a clean upgrade) and still
keep not only your data, but many of your file
configurations
29. /lib
This is the location for shared library files that
are used by system programs
Shared library files are equivalent to Windows'
“*.dll” files
The files here are intended to be libraries for
programs in /bin and /sbin, i.e. needed to
boot the system and run the commands in the
root file system
30. /lib 2
Also in this directory are kernel modules
Other library locations for other programs
include /usr/lib and /usr/local/lib
31. /media, /mnt
Either directory can be a place to mount
removable media (e.g. CD, USB drive, Floppy
disk)
/mnt is the older way, and is still used for
temporarily-mounted file systems
Most current distro versions will mount these
devices automatically
32. /opt
Intended as a place for “optional” software,
i.e. add-on packages that are not part of the
default installation
33. /proc
Have we mentioned that everything in Linux is
a file or a directory?
Any time a process is created in Linux, a
corresponding file goes in here
Gosh, what would happen if you deleted a file
here?
34. /root
Home directory for the root account
Normally, you don't want to be root, and you
don't want to go here
35. /sbin
Place for System binaries
One of three such directories
– /sbin
– /usr/sbin
– /usr/local/sbin
All three hold utilities used for system
administration, and are intended for the root
user like for booting, restoring, recovering,
and/or repairing the system
36. /tmp
Guess what this one is?
Yes, temporary files are placed here
Assume that anything in this directory will be
deleted whenever the system is booted
If you want to have your own temporary
directory and not lose files at reboot, create
one in your home directory, i.e.
/home/username/temp
37. /usr
Lots of stuff in here
Back in the mists of prehistory, these were
the user directories, equivalent to what are
now /home directories
Now /usr is for shareable data
Not intended for software packages, in
general
38. /usr/bin
Contains executable files for many Linux
commands
These are commands that are not part of the
core Linux operating system
They would go in /bin
Examples of commands in here: perl, python
40. /usr/lib
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
41. /usr/local
For use by System Administrator when
installing software locally
Must not be over-written when system
software is updated
Generally has same subdirectories as /usr
44. /usr/src
Source code is placed here, for reference
purposes only
This includes the source code for the Linux
kernel
45. /var
This is for files that are expected to be
updated and changed
This includes:
– mail directories
– print spool
– logs
– web sites
46. /var 2
Because these can be written to constantly,
they can grow over time
On a server, you may want to put /var on its
own partition to limit the growth
This can also prevent the /var directory from
bringing down the server by using up all of
the drive space.
47. /var/lock
Contains lock files
These files prevent two users (or two
programs) from trying to access the same
data at the same time
You may need to delete a lock file from time
to time
