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All the device file are stored in /dev/

Hard disk ; /dev/hdx

Where x is

a : /dev/hda : Primary master

b : /dev/hdb : Primary slave

c : /dev/hdc : Secondary master

d : /dev/hdd : Secondary slave

In case of SCSI, Sata or USB we will use : /dev/sda

CD-rom:

/dev/cdrom

/dev/cdrom1

/dev/cdrecorder

Floppy:

/dev/fd0

/dev/fd1

to access partition of windows in linux

#mount –t vfat /dev/hdax /mnt

in order to check the label of any partition

#e2label /dev/hdax

where x is number

Mounting CD Rom

# mount –t auto /dev/hdc /media/cdrom

-t : file type

auto : file type

in order to check where cdrom is attached we can open the file fstab

#vi /etc/fstab

now in case of RHEl 3.0 we have to use command in order to unmount.

# umount /media/cdrom

and then eject the cdrom

in case of RHEL 4.0 we simply type

# eject

Mounting Floppy

#mount –t auto /dev/fd0 /media/floppy

in case of floppy we have to umount first then only we remove floppy otherwise all content of floppy may be lost or floppy may be physically damaged.

# umount /media/floppy

Mounting USB media :- directed by the kernel as SCSI device

/dev/sdax

Vi Editor:

Using vi , we can create or modify any file

Figure

Root : it is an home directory of super user (root) administrator

Etc : it is the location of all configuration file and directory used for server

configuration or system configuration

dev : it is a location of the device file

home : it is a location of home directory or regular users

proc : it is a virtual file system or directory not actually store on the disk and

contain system information

# cat /proc/meminfo

# cat /proc/cpuinfo

boot : contain kernel and boot related files

sys : it is also a virtual directory and contain system information

media : it is a mount point of removable disk like cdrom floppy usb drive etc.

tmp : it contain all temporary file

usr : it is used for software installation

lib : it contain all library files

bin : it is the location of all executable files or command or user command

/usr/bin also contain user command

sbin : it contain all system command or super user command /usr/sbin

mnt : it is a mount point for physical hard-disk or partition

opt : optional directory and used for temporary working

var : it is a variable file system or directory and contain all log and error

message

file system type:

Dos : Fat 16

95/Xp/2000 : FAT32

Xp/NT/2000 : NTFS

Linux : EXT2,EXT3

UNIX : VXFS

‘ll’ is used to display the information about the files and directory including date, time, users,group, size, name and permission.

Four symbols are used when displaying permission.

R : Read

W : Write

X : Execute

- : no permission

-rwxrwxrwx : files

drwxrwxrwx : directory

files and directory permission are symbolized by ten character.

If we want to change permission, then there are two methods:

1. symbolic
2. Numeric

Syntax:

Chmod mode directory/filename

Mode Option:

1. u,g,o
2. w,r,x
3. +,-
4. =

1. # chmod u+rwx file or directory : in case of user only
2. # chmod ug+rwx file or directoty : in case of user and group
3. # chmod u+w,g+r,o+x directory/file
4. # chmod u+rw,g+rw directory/file
5. # chmod u-r, g-w,o-rw directory/file
6. # chmod ugo+rwx file/directory
7. # chmod ugo-rwx file/directory

• + is used to add permission
• - is used remove permission

chmod ugo=rw directory/file

this command will assign read/write permission to u,g,o

suppose we have one file as

test.txt

permission : -r- - r- -r- -

chmod u=w,g=wx,o=w test.txt

this command will assign write to user, write/execute to group and write to other while remove the previous permission.

The main difference between +,= are + operator simply add the new permission with previous one and = assign the new permission while removing old (new permission overwrite an old)

In this method, calculation are based on following numbers

r=4 w=2 x=1 0= no permission

Example:

#chmod 777 file/directory

in this case user get 7 means that user has permission of read/write/execute, group get 7 means read/write/execute and ame for other

# chmod 531 file/directory

in this case user get 5 means that user has permission of read/execute, group get 3 means write/execute and other get 1 means that other has permission to execute.

#chmod 742 file/directory

7 : User : rwx

4 :Group : r

2 : Other : w

The command that are used to get the help are discussed as :

1. Whatis

Display a short description of command , it uses a database that is updated nightly. Often not available immediately after installation.

Syntax:

# Whatis cal

2. Help

Display usage summary and argument list

Syntax:

--help

Example:

#Date –help

3. Man and Info:

Both provide documentation for command. Almost every command has a “man” page. Collection of pages are called linux manual.

# man date

# info date

Viewing Text Page

Syntax:

#less [option] [filename]

Example:

# less abc.txt

scroll with arrows/PgUp /PgDown

/text : search for text

n : Next Match

Option:

-c : Clear before displaying

-s : Squeeze multiple blank lines into a single blank line

Simply we can also use “less” along with pipe | as

# ll |less

Moving and Renaming File and Directory

Syntax:

# mv : move /rename files and directory

Example:

# mv [option] file destination

example:

# mv t.txt /home/rohan/

more than one file can be moved at a time if the destination is a directory

# mv [option] file1 file2 file3 destination

1. Copy file:

Syntax:

# cp [source]filename [destination]

2. Copy directory

#cp –r [source]directory [destination]

to copy a directory into another directory recursively

3. cp –rf [source]directory [destination]

to copy a directory forcefully

syntax used for copy file or directory:

cp [option] file destination

option:

-I : interactive : ask before overwriting file

-r : Recursive

-p : Preserve

-f : forcefully

More than one file can be copied at a time if the destination is directory

Syntax:

cp [option] file1 file2 file 3 Destination

1. Creating file:

The ‘cat’ command is used to create a file

Syntax:

# cat > filename

example:

# cat > abc.txt

(Ctrl +D) is used to save the file.

2. View the content of file

Syntax:

# cat filename

Example:

#cat abc.txt

#cat –b abc.txt

3. Creating Directory

The ‘mkdir’ command is used to create directory

Syntax:

Mkdir [directory_name]

Example:

# mkdir rohan

Option used:

cd : To change directory

cd .. : To come out from directory

cd : to jump to root directory

cd - : to jump to previous directory

Deleting Files and directory:

Syntax:

For file:

rm

example:

rm abc.txt

for directory

syntax:

rmdir

Note: Only empty directory will be deleted)

If we want to delete the tree structure of directory then we need to use the following command

Syntax:

rm –rf

where

r = recursively

f= force

in order to remove non empty directory

Syntax:

rm –r

example;

rm –r rohan

this will remove directory step by step ,first remove sub directory and then finally main directory.

Touch : this command is used to create a blank file with size zero.

# touch

Example:

#touch abc