Basic Commands

The basic commands that any linux user must know

 

pwd

to view the present working directory

Syntax

[root@bOtskOOl root]#pwd

 

cd

to change the working/present directory

Syntax

[root@bOtskOOl root]#cd /home/student

where '/home/student' is the desired directory to be change from '/root'

 

ls -l

for listing the files as well as directories those are kept in the particular working directory

Syntax

[root@bOtskOOl root]#ls -l

 

ls -la

same as 'ls -l' but by this command we can also see the hidden files.

Syntax

[root@bOtskOOl root]#ls -la

 

ls -li

same as 'ls -la' but it will also shows us the inode number of

each and every file

Syntax

[root@bOtskOOl root]#ls -li

 

ls

by this command we can see only file name nothing else

Syntax

[root@bOtskOOl root]#ls

 

mkdir

to make a new directory

Syntax

[root@bOtskOOl root]#mkdir newdirname

 

rmdir

to remove a empty directory

Syntax

[root@bOtskOOl root]#rmdir directoryname

 

rm

 to remove a empty file

Syntax

[root@bOtskOOl root]#rm filename

rm [-i/-r/-f]

to remove a directory with its subdirectories as well as its

files that is to remove a directory which already contains some files in it

Syntax

[root@bOtskOOl root]#rm -i directory/filename

-i stands for interactively

-r stands for recursively

-f stands for forcefully

 

cp

 to copy something in a destination file or directory

Syntax

[root@bOtskOOl root]#cp sourcepath destinationpath

 

mv

to move one file or directory from one place to another place, it

is also used for renaming a directory or file

Syntax

[root@bOtskOOl root]#mv source destination

[root@bOtskOOl root]#mv oldfilename newfilename [to change the file name]

 

touch

to create a new empty file

Syntax

[root@bOtskOOl root]#touch

 

cat

to view the contents of a file and it is also used for creating a

new file with some contents

Syntax

[root@bOtskOOl root]#cat <file name> to view file contents

[root@bOtskOOl root]#cat > newfilename enter,then you can write something in

the file and then to save the file contents press ctrl+d then enter

 

clear

it will clear the screen(short cut ctrl+l)

Syntax

[root@bOtskOOl root]#clear

 

exit

to end a current session as well current terminal logging

Syntax

[root@bOtskOOl root]exit

 

man

 to view the manual page of commands for syntax and  usage

Syntax

[root@bOtskOOl root]#man commandname

 

info

to view the information about any command

Syntax

[root@bOtskOOl root]#mkdir info

 

--help

to view the help documents of a command

Syntax

[root@bOtskOOl root]#commandname --help

 

find location_to_search_in -name

to find any file or directory in linux file system

Syntax

[root@bOtskOOl root]#find / -name filename

 

su –

to become a super user

Syntax

[student@bOtskOOl student]$su -

output wil be

[root@bOtskOOl root#]

 

su username

to switch from one user to another users home directory

Syntax

[root@bOtskOOl root]#su student

output will be

[student@bOtskOOl root]#cd

[student@bOtskOOl student]#

 

su - username

to switch from one user to another user users home directory directly

Syntax

[root@bOtskOOl root]#su - student

 

useradd

to create a new user

Syntax

[root@bOtskOOl root]#useradd username

 

passwd

to give a password of a user

Syntax

[root@bOtskOOl root]#passwd nitesh

output will be

give a password for user nitesh:(here you have to type a password for nitesh user)

confirm password:(again type the same password)

 

userdel

to remove a user from linux

Syntax

[root@bOtskOOl root]#userdel nitesh

 

groupadd

to add a new group

Syntax

[root@bOtskOOl root]#groupadd groupname

 

groupdel

to delete a group

Syntax

[root@bOtskOOl root]#groupdel groupname

 

chown

to change the ownership of a file or directory

Syntax

[root@bOtskOOl root]#chown ownername filename

example:

[root@bOtskOOl /]#ls -l

output

drwxrw-rw- 2 root root 4096 Mar 11 12:03 abcd

(permission) (own) (group own)(size) (name)

[root@bOtskOOl root]#chown nitesh /abcd

in this example /abcd directory owner will be change to nitesh user

effect

[root@bOtskOOl /]#ls -l

drwxrw-rw- 2 nitesh root 4096 Mar 11 12:03 abcd

 

chgrp

to change the group ownership of a file or directory

Syntax

[root@nettec root]#chgrp newgroupownername filename

example

[root@bOtskOOl /]#ls -l

drwxrw-rw- 2 nitesh root 4096 Mar 11 12:03 abcd

[root@bOtskOOl root]#chgrp nitesh /abcd

effect

[root@bOtskOOl /]#ls -l

drwxrw-rw- 2 nitesh nitesh 4096 Mar 11 12:03 abcd

 

chmod

to change the permission of a file or directory

Syntax

[root@bOtskOOl root]#chmod value fileordirectoryname

example

[root@bOtskOOl /]#ls -l

drwxrw-rw- 2 nitesh root 4096 Mar 11 12:03 abcd

[root@bOtskOOl /]#chmod 402 /abcd

[root@bOtskOOl /]#ls –l

drw-----w- 2 nitesh nitesh 4096 Mar 11 12:03 abcd