Linux Commands

From windows machine you connect to linux PC using telnet or ssh via putty.
You must login using your credentials.

Create Directory:
mkdir <dir name>

Change Directory Path
cd <dir name>

Create a File
Reach the particular directory under which you want to create a file and then issue this command
vi <file name>

While coming our of the file isuue :wq to save the changes and come out
Issue :q! to come out without saving the changes

Delete File
rm <file name>

Delete Directory
rmdir <dir name>
Note that there should be no files under the directory for it to be deleted using this command

List
ls -lrt

Search
To search for a pattern of a file name, issue this command under the required directory

ls *<pattern>*

To search for a file containing a particular content pattern issue this command under the required directory

grep <pattern> *

To search for a file containing a pattern recursively from a directory (if you dont know in which directory the file would be present

find . | xargs grep "pattern"

Other useful linux commands:-
~~~~~~~~~~~~~~~~~~~~~~

To kill a process:-

ps -ef  | grep <process name>
process id will be displayed.
Then kill the process using the command
kill <pid>

We can also kill  the process in a single line:-
pkill <processName>


To Enable different services for different protocols
~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  1. FTP - vsftpd
service vsftpd start

2. TELNET - xinetd


service xinetd start

3. SMTP - send mail
4. HTTP - httpd

service httpd start

5. RADIUS - radiusd

service radiusd start

6. DNS - named
service named start

7. IMAP4 - xinetd
service xinetd start

8. MMS -
9. LDAP - ldap
service ldap start

10. RTSP

Ports and Port Numbers
~~~~~~~~~~~~~~~~~~~~
 1. FTP - 21
2. TELNET - 23
3. SMTP - 25
4. HTTP - 80
5. RADIUS - 1812
6. DNS - 53
7. IMAP4 - 143
8. MMS - 1755
9. LDAP - 389
10. RTSP - 554

Command to send fragmented icmp traffic
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

ping 172.26.64.213 -c 3 -s 2000


-c - count
-s - size

Command to drop SYN packets in the lnux PC using ip tables
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

iptables -A INPUT --protocol tcp --tcp-flags ALL SYN -j DROP

To flush the iptables
~~~~~~~~~~~~~~
iptables -F

Command to test with tethereal

tethereal -i eth1 tcp &

Command to unconfigure or flush an Ethernet interface ip in linux

ip addr flush eth1

ip addr del eth1 <ip>