Linux Commands

Basic Commands

1.ls -l for listing the files as well as directories those are kept in the particular working directory

syntax

[root@nettech root]#ls -l

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

syntax

[root@nettech root]#ls -la

3.ls -li same as 'ls -la' but it will also shows us the inode number of each and every file

syntax

[root@nettech root]#ls -li

4.ls by this command we can see only file name nothing else

syntax

[root@nettech root]#ls

5.clear it will clear the screen(short cut ctl+l)

syntax

[root@nettech root]#clear

6.exit to end a current session as well current terminal logging

syntax

[root@nettech root]exit

7.touch to create a new empty file

syntax

[root@nettech root]#touch

8.cd to change the working/present directory

syntax

[root@nettech root]#cd /home/mango

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

'/root'

9.cat to view the contents of a file and it is also used for creating a new file with some contents

syntax

[root@nettech root]#cat to view file contents

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

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

10.mkdir to make a new directory

syntax

[root@nettech root]#mkdir newdirname

you can also create a directory at your desired path without changing your present working directory

syntax

[root@nettech root]#mkdir /home/mango/newdirname

11.rm to remove a empty file

syntax

[root@nettech root]#rm filename

12.rmdir to remove a empty directory

syntax

[root@nettech root]#rmdir directoryname

13.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@nettech root]#rm -i directory/filename

-i stands for interactively

-r stands for recursively

-f stands for forcefully

14.cp to copy something in a destination file or directory

syntax

[root@nettech root]#cp sourcepath destinationpath

example: [root@nettech root]#cp /home/mango/webmin.rpm /root/abcd

in this example the webmin.rpm file will be copied in

/root/abcd directory

15.mv to move one file or directory from one place to another place, it is also used for renaming adirectory or file

syntax

[root@nettech root]#mv source destination

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

16.man to view the mannual page of commands for syntax

syntax

[root@nettech root]#man commandname

17.info to view the information about any command

syntax

[root@nettech root]#mkdir info

18.--help to view the help doccuments of a command

syntax

[root@nettech root]#commandname --help

19.dir to view the subdirectories and filesn under the directory

syntax

[root@nettech root]#dir

20.su - to become a super user

syntax

[mango@nettech mango]$su -

output wil be

[root@nettech root#]

21.who by this command you can see the user name and their ip addresses who have loged in on your server

syntax

[root@nettech root]#who

22.whoami this command shows your current logged in terminal user name

syntax

[root@nettech root]#whoami

23.who am i this command shows you the logged in terminal number and user name and more detailed information

syntax

[root@nettech root]#who am i

24.pwd to view the present working directory

syntax

[root@nettech root]#pwd

25.rpm -ivh to intall a rpm package

syntax

[root@nettech root]#rpm -ivh packagename.rpm

rpm stands for 'redhat package manager'

-i stands for install

-v stands for verbose mode

-h stands for with hash sign(#)

26.rpm -q to querry about any rpm package

syntax

[root@nettech root]#rpm -q packagename

27.rpm -e to uninstall a rpm package

synatx

[root@nettech root]#rpm -e package

28.find / -name to find any file or directory in linux file system

syntax

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

29.su username to switch from one user to another users home directory

syntax

[root@nettech root]#su mango

output will be

[mango@nettech root]#cd

[mango@nettech mango]#

30.su - username to switch from one user to another user users home directory directly

syntax

[root@nettech root]#su - mango

31.useradd to create a new user

synatx

[root@nettech root]#useradd username

32.passwd to give a password of a user

syntax

[root@nettech root]#passwd tarun

output will be

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

confirm password:(again type the same password)

33.userdel to remove a user from linux

syntax

[root@nettech root]#userdel tarun

34.groupadd to add a new group

syntax

[root@nettech root]#groupadd groupname

35.gruopdel to delete a group

syntax

[root@nettech root]#groupdel groupname

36.chown to change the ownership of a file or directory

syntax

[root@nettech root]#chown ownername filename

example:

[root@nettech /]#ls -l

output

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

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

[root@nettech root]#chown tarun /abcd

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

effect

[root@nettech /]#ls -l

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

37.chgrp to change the group ownership of a file or directory

syntax

[root@nettec root]#chgrp newgroupownername filename

example

[root@nettech /]#ls -l

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

[root@nettech root]#chgrp tarun /abcd

effect

[root@nettech /]#ls -l

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

38.chmod to change the permission of a file or directory

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

(permission) (ownr) (grpownr) (size) (name) IN

OCTAL VALUE

d stands for directiry READ=4

r stands for read only permission WRITE=2

w stands for write only permission EXECUTE=1

x stands for execute only permission

drwxrw-rw- FIRST OCTET FOR DENOTING THE DIRECTORY OR FILE OR LINK FILE ETC.

SECOND THREE OCTET FOR USER OR OWNER PERMISSION (rwx OR 7 IN

OCTAL VALUE)

THIRD THREE OCTET FOR GROUP PERMISSION (rw- OR 6 IN OCTAL VALUE)

FORTH THREE OCTET FOR OTHERS PERMISSION (rw- OR 6 IN OCTAL VALUE)

syntax

[root@nettec root]#chmod value fileordirectoryname

example

[root@nettech /]#ls -l

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

[root@nettech /]#chmod 402 /abcd

[root@nettech /]#ls -l

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

39.usermod to modify the user profile

synatx

[root@nettech root]#usermod -parameter groupname username