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Wednesday, July 3, 2019

Linux Basic Commands

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

syntax
[root@mars root]#ls -l

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

syntax
[root@mars 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@mars root]#ls -li

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

syntax
[root@mars root]#ls

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

syntax
[root@mars root]#clear

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

syntax
[root@mars root]exit

7.touch to create a new empty file

syntax
[root@mars root]#touch

8.cd to change the working/present directory

syntax
[root@mars root]#cd /home/apple
where '/home/apple' 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@mars root]#cat <file name> to view file contents
[root@mars 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@mars root]#mkdir newdirname
you can also create a directory at your desired path without
changing your present working directory

syntax
[root@mars root]#mkdir /home/apple/newdirname

11.rm to remove a empty file

syntax
[root@mars root]#rm filename

12.rmdir to remove a empty directory

syntax
[root@mars 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@mars 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@mars root]#cp sourcepath destinationpath
example: [root@mars root]#cp /home/apple/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@mars root]#mv source destination
[root@mars root]#mv oldfilename newfilename [to change the file name]


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

syntax
[root@mars root]#man commandname

17.info to view the information about any command

syntax
[root@mars root]#mkdir info

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

syntax
[root@mars root]#commandname --help

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

syntax
[root@mars root]#dir

20.su - to become a super user

syntax
[apple@mars apple]$su -
output wil be
[root@mars 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@mars root]#who

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

syntax
[root@mars root]#whoami

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

syntax
[root@mars root]#who am i

24.pwd to view the present working directory

syntax
[root@mars root]#pwd

25.rpm -ivh to intall a rpm package

syntax
[root@mars 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@mars root]#rpm -q packagename

27.rpm -e to uninstall a rpm package

synatx
[root@mars root]#rpm -e package

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

syntax
[root@mars root]#find / -name filename

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

syntax
[root@mars root]#su apple

output will be
[apple@mars root]#cd
[apple@mars apple]#
30.su - username to switch from one user to another user users home
directory directly

syntax
[root@mars root]#su - apple

31.useradd to create a new user

synatx
[root@mars root]#useradd username

32.passwd to give a password of a user

syntax
[root@mars 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@mars root]#userdel tarun

34.groupadd to add a new group

syntax
[root@mars root]#groupadd groupname

35.gruopdel to delete a group

syntax
[root@mars root]#groupdel groupname

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

syntax
[root@mars root]#chown ownername filename
example:
[root@mars /]#ls -l
output
drwxrw-rw- 2 root root 4096 Mar 11 12:03 abcd
(permission) (own) (group own)(size) (name)
[root@mars root]#chown tarun /abcd
in this example /abcd directory owner will be change to tarun user
effect
[root@mars /]#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@mars /]#ls -l
drwxrw-rw- 2 tarun root 4096 Mar 11 12:03 abcd
[root@mars root]#chgrp tarun /abcdeffect
[root@mars /]#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@mars /]#ls -l
drwxrw-rw- 2 tarun root 4096 Mar 11 12:03 abcd

[root@mars /]#chmod 402 /abcd

[root@mars /]#ls -l
drw-----w- 2 tarun tarun 4096 Mar 11 12:03 abcd
40.usermod to modify the user profile

synatx
[root@mars root]#usermod -parameter groupname username

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