Wednesday, December 21, 2011

Install and Uninstall VMware .bundle in Redhat - RHEL 6

Here the steps for Install and Uninstall VMware .bundle in Redhat and also Linux. I have checked with RHEL 6.

For install :
Login in as root user, Type following command

~]# sh VMware-***.bundle

Here *** will be your software and it's version.

This command will display normal GUI installation. Choose option as your wish.

For Uninstall :
Login in as root user, Type following command

~]# vmware-installer -l

This will display your product name and product version installed by VMware.

Product Name         Product Version    
========== ==============

Note Name and Version, Use following command to uninstall

~]# vmware-installer -u {product-name} {product-version}

~]# vmware-installer -u vmware-workstation

Now you can uninstall with GUI.

* This is common for all VMware .bundle installation files. Ex: VMware-Workstation, VMware-Player etc.

Tuesday, December 13, 2011

Clear Samba Passwords from Windows

Following command will use to clear samba user name and passwords in windows.

net use /delete \\

* Replace with your samba server address.

* Can use this command with command prompt or with "Run" Directly.

* You can create this command with .bat file for single click delete.

Thursday, August 18, 2011

User accounts in Linux

Super User in Linux

Super User is the user with all rights for accessing all files, Like Windows Administrator. Here the super user is "root".

This user have all rights to access all files including system files. Should be careful if you are root. It can delete any files. So it may crash total system.

The root user can be created at the time of installation.

Adding User in Linux

The root user can add user to Linux box. Following command can be used for adding user in Linux.

[root@LocalHost ~]#useradd kumar

For setup password, Following command can be used,

[root@LocalHost ~]#passwd kumar
Changing password for user kumar.
New UNIX password:
Retype new UNIX password:
passwd: all authentication tokens updated successfully.

You'll get a warning message if you give any dictionary word.
"BAD PASSWORD: it is based on a dictionary word"

You can create user without password, also can disable password for a user. Passwordless account.

[root@LocalHost ~]#passwd -d kumar
Removing password for user kumar.
passwd: Success

For more details use man pages of useradd and passwd.

Every user have home directory as the user name, location is /home/{user name}.

Delete User

Following command is used to delete user,

[root@LocalHost ~]#userdel kumar

It delete user alone, home directory will be avaliable in /home/

For delete home diectory of the user, we use the option -r.
For delete the user forcely , we use the option -f.

User Groups

We can add groups in Linux, Groups are used for permission to accessing files and security. Group have one or more users.

For add group,

[root@LocalHost ~]#groupadd adminnote

When we create a user it automatically create group in the same user name. Every users must be in group, Every user have one primary group and may or may not secondary group. For Example, kumar is the user and he should be in the group kumar, It's primary group of the user kumar. And the user kumar may or may not in the group adminnote.

For checking group of the user, try following command.

[root@LocalHost ~]#groups kumar
kumar : kumar

For more details about this refere some Books of Linux.

Wednesday, August 3, 2011

Basic in Linux

Linux is one of the operation system. We can tell it as UNIX like operating system. It is open source, It come under GNU public license. We can use it as free. For more and updated details about Linux try Wikipedia.

Now we'll go for learning Linux throw command line, Before go administration these are some basics,


The terminal is using for executing commends in Linux box. If we open terminal, it looks as bellow

[kumar@LocalHost ~]$

Here "kumar" is user account in Linux box. "LocalHost" is host name of your system, that means your system name. Normally till (~) symbol mention home directory of the logged user. If you are as root user , it looks as bellow

[root@LocalHost ~]#

Here you can see a difference in both things, that is dollar ($) symbol and Hash (#). There normal user have $ symbol at end and root user have # symbol at the end. This is easily to identify which user we have logged.

Executable commends in Linux are stored in /bin and /sbin directories. The normal user are can access only commends under /bin , They can's use /sbin commends. But the root user can access both /bin and /sbin directory commends.

root is the administrator account. If we made and mistakes while in root account, there is chance to crash hole system.


man is a very basic command in Linux box. We normal know it as man pages. The man pages are manual of commands. most of the commands in Linux have man pages. It describe all about commands. The syntax of the man page is "man {command}"

[kumar@LocalHost ~]$man ls 


ls is the basic command in Linux box, ls is used to list files.
[kumar@LocalHost ~]$ ls
[kumar@LocalHost ~]$

Here we didn't create any files, so it didn't give any output.


cat command is used to show the file. And also this is used to create and append the file.

cat {FileName} - Open file
cat > {FileName} - Create file
cat >> {FileName} - Append file
[kumar@LocalHost ~]$ cat > filename
hi this is my first file

[kumar@LocalHost ~]$ cat filename
hi this is my first file
[kumar@LocalHost ~]$ cat >> filename
this is additional lines

[kumar@LocalHost ~]$ cat filename
hi this is my first file
this is additional lines
[kumar@LocalHost ~]$

"ctrl + c" used to quit file, It'll save and exit from cat.

We can't edit already created file with "cat" command. For this we are going for other editors available in Linux.
ex: vi, vim etc.,

Before we going to editors we'll see the "ls" command, As seen before ls is the command used for list file in Linux,

[kumar@LocalHost ~]$ ls
[kumar@LocalHost ~]$

This is the file we created as before by "cat".

[kumar@LocalHost ~]$ ls -l
total 4
-rw-rw-r-- 1 kumar kumar 50 Aug  3 11:47 filename

Here -l is the option for ls command, It give some detailed information about the file or directory.

"total 4" is blocks used by the file "filename".

"-rw-rw-r--" is about file permission, we'll see about it later.
"1" is about file count.
"kumar" is owner of file
"kumar" is group under this file
"50"  file size
"Aug 3 11.47" file creation date and time
"filename" name of the file

for more option try man pages and try more,


mkdir is the command used to create folder in Linux box.
[kumar@LocalHost ~] mkdir myfolder


rm is the command used to remove folder or file.
rm {filename}

-f used to force the deletion, it won't ask conformation
-r used for recursive deletion, i meant it used to delete entire folder

[kumar@LocalHost ~] rm -f filename
[kumar@LocalHost ~] rm -fr myfolder

vim is the editor, It is advance version of the vi editor. vim editor can be used to create, edit and update file.

[kumar@LocalHost ~] vim newfile

It'll open editor window, Normally it in uneditable mode. By press "i" key we can move to edit mode, to quit from edit mode, press "esc" key.
After finish typing, press "esc" key and type ":wq" for save and quit. Here w for save and q for quid vim. We can use this command separately. For quit without changes, ":q!".

For more options try man pages.

Tuesday, July 19, 2011

Add module (driver) while installing RHEL 5

It's an interview question for Linux System Administrator,

You want to install RHEL 5 operating system on server machine. Unfortunately RHEL 5 doesn't detect your hard disk. But you need to install it on that hard disk. How will you do ? You have module disk ( Driver CD/DVD) for that hard disk and RHEL 5 DVD.

I felt this is too hard and searched in several places, But actually it's simple thing, ( I didn't try practically because i don't have that much advance or old hard disk). Ok let us see those very simple steps.
Step 1 : Insert the RHEL 5 CD/DVD and boot from CD/DVD. We will get following screen,

Redhat Boot Screen
click image for zoom

Step 2 : There is submenu , Press F2 for show Installer boot options, It's look like as bellow,

Installer Boot Options
click image for zoom
Step 3 : Type "linux dd" and hit enter, you'll get following screen. "linux dd" use to load driver disk,

Driver Disk
click image for zoom
Step 4 : It asks whether you have driver disk or not. Select Yes and hit enter. you'll get following screen.

Insert Driver Disk
click image for zoom

Step 5 : Insert your Driver Disk and hit enter. It'll install needed driver from disk.

Now your Hard Disk is detected by the RHEL 5 CD/DVD. Now we can install OS in this Hard Disk.

* Still I not use this method. Hope this will work. If you face this problem. Try and commant me.

Thursday, June 16, 2011

Keyboard shortcuts for Word 2003 and Word 2007

Command Name                  Shortcut Keys

   All Caps                      CTRL+SHIFT+A
   Annotation                    ALT+CTRL+M
   App Maximize                  ALT+F10
   App Restore                   ALT+F5
   Apply Heading1                ALT+CTRL+1
   Apply Heading2                ALT+CTRL+2
   Apply Heading3                ALT+CTRL+3
   Apply List Bullet             CTRL+SHIFT+L
   Auto Format                   ALT+CTRL+K
   Auto Text                     F3 or ALT+CTRL+V
   Bold                          CTRL+B or CTRL+SHIFT+B
   Bookmark                      CTRL+SHIFT+F5
   Browse Next                   CTRL+PAGE DOWN
   Browse Previous               CTRL+PAGE UP
   Browse Sel                    ALT+CTRL+HOME
   Cancel                        ESC
   Center Para                   CTRL+E
   Change Case                   SHIFT+F3
   Char Left                     LEFT
   Char Left Extend              SHIFT+LEFT
   Char Right                    RIGHT
   Char Right Extend             SHIFT+RIGHT
   Clear                         DELETE
   Close or Exit                 ALT+F4
   Close Pane                    ALT+SHIFT+C
   Column Break                  CTRL+SHIFT+ENTER
   Column Select                 CTRL+SHIFT+F8
   Copy                          CTRL+C or CTRL+INSERT
   Copy Format                   CTRL+SHIFT+C
   Copy Text                     SHIFT+F2
   Create Auto Text              ALT+F3
   Customize Add Menu            ALT+CTRL+=
   Customize Keyboard            ALT+CTRL+NUM +
   Customize Remove Menu         ALT+CTRL+-
   Cut                           CTRL+X or SHIFT+DELETE
   Date Field                    ALT+SHIFT+D
   Delete Back Word              CTRL+BACKSPACE
   Delete Word                   CTRL+DELETE
   Dictionary                    ALT+SHIFT+F7
   Do Field Click                ALT+SHIFT+F9
   Doc Close                     CTRL+W or CTRL+F4
   Doc Maximize                  CTRL+F10
   Doc Move                      CTRL+F7
   Doc Restore                   CTRL+F5
   Doc Size                      CTRL+F8
   Doc Split                     ALT+CTRL+S
   Double Underline              CTRL+SHIFT+D
   End of Column                 ALT+PAGE DOWN
   End of Column                 ALT+SHIFT+PAGE DOWN
   End of Doc Extend             CTRL+SHIFT+END
   End of Document               CTRL+END
   End of Line                   END
   End of Line Extend            SHIFT+END
   End of Row                    ALT+END
   End of Row                    ALT+SHIFT+END
   End of Window                 ALT+CTRL+PAGE DOWN
   End of Window Extend          ALT+CTRL+SHIFT+PAGE DOWN
   Endnote Now                   ALT+CTRL+D
   Extend Selection              F8
   Field Chars                   CTRL+F9
   Field Codes                   ALT+F9
   Find                          CTRL+F
   Font                          CTRL+D or CTRL+SHIFT+F
   Font Size Select              CTRL+SHIFT+P
   Footnote Now                  ALT+CTRL+F
   Go Back                       SHIFT+F5 or ALT+CTRL+Z
   Go To                         CTRL+G or F5
   Grow Font                     CTRL+SHIFT+.
   Grow Font One Point           CTRL+]
   Hanging Indent                CTRL+T
   Header Footer Link            ALT+SHIFT+R
   Help                          F1
   Hidden                        CTRL+SHIFT+H
   Hyperlink                     CTRL+K
   Indent                        CTRL+M
   Italic                        CTRL+I or CTRL+SHIFT+I
   Justify Para                  CTRL+J
   Left Para                     CTRL+L
   Line Down                     DOWN
   Line Down Extend              SHIFT+DOWN
   Line Up                       UP
   Line Up Extend                SHIFT+UP
   List Num Field                ALT+CTRL+L
   Lock Fields                   CTRL+3 or CTRL+F11
   Macro                         ALT+F8
   Mail Merge Check              ALT+SHIFT+K
   Mail Merge Edit Data Source   ALT+SHIFT+E 
   Mail Merge to Doc             ALT+SHIFT+N
   Mail Merge to Printer         ALT+SHIFT+M
   Mark Citation                 ALT+SHIFT+I
   Mark Index Entry              ALT+SHIFT+X
   Mark Table of Contents Entry  ALT+SHIFT+O
   Menu Mode                     F10
   Merge Field                   ALT+SHIFT+F
   Microsoft Script Editor       ALT+SHIFT+F11
   Microsoft System Info         ALT+CTRL+F1
   Move Text                     F2
   New                           CTRL+N
   Next Cell                     TAB
   Next Field                    F11 or ALT+F1
   Next Misspelling              ALT+F7
   Next Object                   ALT+DOWN
   Next Window                   CTRL+F6 or ALT+F6
   Normal                        ALT+CTRL+N
   Normal Style                  CTRL+SHIFT+N or ALT+SHIFT+CLEAR (NUM 5)
   Open                          CTRL+O or CTRL+F12 or ALT+CTRL+F2
   Open or Close Up Para         CTRL+0
   Other Pane                    F6 or SHIFT+F6
   Outline                       ALT+CTRL+O
   Outline Collapse              ALT+SHIFT+- or ALT+SHIFT+NUM -
   Outline Demote                ALT+SHIFT+RIGHT
   Outline Expand                ALT+SHIFT+=
   Outline Expand                ALT+SHIFT+NUM +
   Outline Move Down             ALT+SHIFT+DOWN
   Outline Move Up               ALT+SHIFT+UP
   Outline Promote               ALT+SHIFT+LEFT
   Outline Show First Line       ALT+SHIFT+L
   Overtype                      INSERT
   Page                          ALT+CTRL+P
   Page Break                    CTRL+ENTER
   Page Down                     PAGE DOWN
   Page Down Extend              SHIFT+PAGE DOWN
   Page Field                    ALT+SHIFT+P
   Page Up                       PAGE UP
   Page Up Extend                SHIFT+PAGE UP
   Para Down                     CTRL+DOWN
   Para Down Extend              CTRL+SHIFT+DOWN
   Para Up                       CTRL+UP
   Para Up Extend                CTRL+SHIFT+UP
   Paste                         CTRL+V or SHIFT+INSERT
   Paste Format                  CTRL+SHIFT+V
   Prev Cell                     SHIFT+TAB
   Prev Field                    SHIFT+F11 or ALT+SHIFT+F1
   Prev Object                   ALT+UP
   Prev Window                   CTRL+SHIFT+F6 or ALT+SHIFT+F6
   Print                         CTRL+P or CTRL+SHIFT+F12
   Print Preview                 CTRL+F2 or ALT+CTRL+I
   Proofing                      F7
   Redo                          ALT+SHIFT+BACKSPACE
   Redo or Repeat                CTRL+Y or F4 or ALT+ENTER
   Repeat Find                   SHIFT+F4 or ALT+CTRL+Y
   Replace                       CTRL+H
   Reset Char                    CTRL+SPACE or CTRL+SHIFT+Z
   Reset Para                    CTRL+Q
   Revision Marks Toggle         CTRL+SHIFT+E
   Right Para                    CTRL+R
   Save                          CTRL+S or SHIFT+F12 or ALT+SHIFT+F2
   Save As                       F12
   Select All                    CTRL+A or CTRL+CLEAR (NUM 5) or CTRL+NUM 5
   Select Table                  ALT+CLEAR (NUM 5)
   Show All                      CTRL+SHIFT+8
   Show All Headings             ALT+SHIFT+A
   Show Heading1                 ALT+SHIFT+1
   Show Heading2                 ALT+SHIFT+2
   Show Heading3                 ALT+SHIFT+3
   Show Heading4                 ALT+SHIFT+4
   Show Heading5                 ALT+SHIFT+5
   Show Heading6                 ALT+SHIFT+6
   Show Heading7                 ALT+SHIFT+7
   Show Heading8                 ALT+SHIFT+8
   Show Heading9                 ALT+SHIFT+9
   Shrink Font                   CTRL+SHIFT+,
   Shrink Font One Point         CTRL+[
   Small Caps                    CTRL+SHIFT+K
   Space Para1                   CTRL+1
   Space Para15                  CTRL+5
   Space Para2                   CTRL+2
   Spike                         CTRL+SHIFT+F3 or CTRL+F3
   Start of Column               ALT+PAGE UP
   Start of Column               ALT+SHIFT+PAGE UP
   Start of Doc Extend           CTRL+SHIFT+HOME
   Start of Document             CTRL+HOME
   Start of Line                 HOME
   Start of Line Extend          SHIFT+HOME
   Start of Row                  ALT+HOME
   Start of Row                  ALT+SHIFT+HOME
   Start of Window               ALT+CTRL+PAGE UP
   Start of Window Extend        ALT+CTRL+SHIFT+PAGE UP
   Style                         CTRL+SHIFT+S
   Subscript                     CTRL+=
   Superscript                   CTRL+SHIFT+=
   Symbol Font                   CTRL+SHIFT+Q
   Thesaurus                     SHIFT+F7
   Time Field                    ALT+SHIFT+T
   Toggle Field Display          SHIFT+F9
   Toggle Master Subdocs         CTRL+\ 
   Tool                          SHIFT+F1
   Un Hang                       CTRL+SHIFT+T
   Un Indent                     CTRL+SHIFT+M
   Underline                     CTRL+U or CTRL+SHIFT+U
   Undo                          CTRL+Z or ALT+BACKSPACE
   Unlink Fields                 CTRL+6 or CTRL+SHIFT+F9
   Unlock Fields                 CTRL+4 or CTRL+SHIFT+F11
   Update Auto Format            ALT+CTRL+U
   Update Fields                 F9 or ALT+SHIFT+U
   Update Source                 CTRL+SHIFT+F7
   VBCode                        ALT+F11
   Web Go Back                   ALT+LEFT
   Web Go Forward                ALT+RIGHT
   Word Left                     CTRL+LEFT
   Word Left Extend              CTRL+SHIFT+LEFT
   Word Right                    CTRL+RIGHT
   Word Right Extend             CTRL+SHIFT+RIGHT
   Word Underline                CTRL+SHIFT+W
source :

Saturday, June 11, 2011

Windows XP Hidden apps

Following comments are execute throw run command box,

  1. Character Map = charmap.exe (Useful for finding characters)
  2. Disk Cleanup = cleanmgr.exe (Clean temp / compressed files)
  3. Clipboard Viewer = clipbrd.exe (Views contents of clipboard)
  4. Dr Watson = drwtsn32.exe (Troubleshooting tool for windows xp)
  5. DirectX diagnosis = dxdiag.exe (Diagnose & test DirectX, video & sound cards)
  6. Private character editor = eudcedit.exe (allows creation or modification of characters)
  7. IExpress Wizard = iexpress.exe (Create the self-extracting / self-installing packages for windows)
  8. Microsoft Synchronization Manager = mobsync.exe (appears to allow synchronization of files on the network for when working offline. Apparently undocumented)
  9. Windows Media Player 5.1 = mplay32.exe (Retro version of Media Player)
  10. ODBC Data Source Administrator = odbcad32.exe (Database connectivity)
  11. Object Packager = packager.exe (to do with packaging objects for insertion in files, appears to have comprehensive help files)
  12. System Monitor = perfmon.exe (To know about PC performance)
  13. Program Manager = progman.exe (Legacy windows 3.x desktop shell) // didn't work for me.
  14. Remote Access phone book = rasphone.exe (documentation is virtually non-existant)
  15. Registry Editor = regedt32.exe or regedit.exe (For edit windows registry)
  16. Network shared folder wizard = shrpubw.exe (creates shared folders on network)
  17. File siganture verification tool = sigverif.exe
  18. Volume Control = sndvol32.exe
  19. System Configuration Editor = sysedit.exe (for edit System.ini & Win.ini)
  20. Syskey = syskey.exe (Secures XP Account database - use with care, it's virtually undocumented but it appears to encrypt all passwords)
  21. Microsoft Telnet Client = telnet.exe
  22. Driver Verifier Manager = verifier.exe (Utility for monitoring the actions of drivers)
  23. windows for Workgroups Chat = winchat.exe (chat sessions over a LAN)
  24. System configuration = msconfig.exe (can use to control starup programs)
  25. gpedit.msc used to manage group policies, and permissions..!

Saturday, May 14, 2011

Clear Recent Documents in with History Manager for Linux

Here the steps for clearing recent documents list in

History Manager is the add-on for We are using this add-on for clearing recent documents.

Step  1 : Download the add-on from here.
Step  2 : Save it anywhere you like.
Step  3 : Open the application writer
Step  4 : Go to tools -> Extension Manager
Step  5 : It'll open new window, here click "add" button and choose the file which you downloaded at 1st step.
Step  6 : It may or may not ask for "Only for me" or "For all user". Choose your wish.
Step  7 : It shows agreement, scroll down and click accept button.
Step  8 : Restart the writer.
Step  9 : Go to tools -> Add-on -> History Manager
Step 10: Allocate your history size and click OK, If want to clear history, set "0" and click OK

Wednesday, April 6, 2011

Telnet on RedHat

Telnet is a network protocol used on the Internet or local area networks to provide a bidirectional interactive text-oriented communications facility using a virtual terminal connection. User data is interspersed in-band with Telnet control information in an 8-bit byte oriented data connection over the Transmission Control Protocol (TCP).

Installing Telnet on Redhat:
yum is the easy way to installing telnet on redhat. You can use DVD repository if don't have RHN support.

#yum install telnet*

It'll install both server and client of telnet.

Enabling/Configuring telnet on RedHat

Open "/etc/xinetd.d/telnet" file using any editor,

Ex. #vim /etc/xinetd.d/telnet

In this file want to change "disable = yes" to "disable = no"

For restarting telnet service run following command, If getting error on stoping service ignore it

#service xinetd restart 
#chkconfig xinetd on

Now you can connect telnet server by telnet client on network.

Telnet client
In Linux, open terminal and run this command,  #telnet SERVER_IP
In Windows, open dos prompt,  >telnet SERVER_IP

Tuesday, April 5, 2011

IpTables - The Linux Firewall

Introduction :
IpTables is the user space program , which is used create rules for packet filtering. IpTables used for create Firewall rules in Linux System. Before going to IpTables , first we want to get some knowledge about Firewall.

A firewall is a device or set of devices designed to permit or deny network transmissions based upon a set of rules and is frequently used to protect networks from unauthorized access. Many personal computer operating systems (windows, linux, mac, etc) include software-based firewalls to protect against threats from the public Internet. Many routers that pass data between networks contain firewall components and, conversely, many firewalls can perform basic routing functions.

Installation on linux:

Before going to installation , we need to check whether our kernel was compiled with iptables support. Follwoing steps are used to check.

# cat /boot/ | grep -i "CONFIG_IP_NF_IPTABLES"

If we get the display as CONFIG_IP_NF_IPTABLES=m , Our Kernel was compiled with iptables support. '=m' means iptables was compiled as a module.

First we need to check whether the iptables installed already. Here i'm using redhat enterprice linux. So using the command as follows,

# rpm -qa | grep iptables.

If you get output like iptables-INSTALLED-VERSION , Or you need to install iptables.

For installation, download iptables file from internet , or install using yum.

# rpm -qa | grep iptables
# rpm -Uvh iptables-downloaded.version.rpm

Importent files for iptables

/etc/init.d/iptables is the INIT script which is used to start, stop the service and/or to save the rulesets.
/etc/sysconfig/iptables this is the file that holds the saved rulesets.
/sbin/iptables and this is the iptables binary.

Checking current configuration

#iptables -L

There are 3 default chains avaliable. INPUT, OUTPUT, FORWARD.
INPUT - Rules for incoming traffic to server.
OUTPUT - Rules for outgoing traffic from server to Internet.
FORWARD - Rules for traffic forward to chients or server on network (LAN...).

When traffic moves through Linux kernel, a TARGET is determined by whether the packet matches a rule in the rulesets or not. There are three main targets are avaliable.

ACCEPT - Traffic is allowed to pass through linux server to its destination.
REJECT - Traffic is blocked from its destination and a packet is sent back to the sending host with a explanation by linux server.
DROP - Traffic is blocked with no explanation (Like closing connection).

Before going to configure new ruleset , following things are very importent.

Should know the order of rules going to add in ruleset. If order changes , It will give very bad results sometime. If your first rule is to deny everything... then no matter what you specifically allow, it will be denied.

Rule set is not active till you save rule. It will be done by seprate command.

If you are using ssh for configure iptables on remote server, first you shoud allow yourself.

Basic Iptables Options

Here are some of the iptables options.

-A - Append this rule to a rule chain. Valid chains for what we're doing are INPUT, FORWARD and OUTPUT, but we mostly deal with INPUT in this tutorial, which affects only incoming traffic.

-L - List the current filter rules.

-m conntrack - Allow filter rules to match based on connection state. Permits the use of the --ctstate option.
   --ctstate - Define the list of states for the rule to match on. Valid states are:
         NEW - The connection has not yet been seen.
         RELATED - The connection is new, but is related to another connection already permitted.
         ESTABLISHED - The connection is already established.
         INVALID - The traffic couldn't be identified for some reason.

-m limit - Require the rule to match only a limited number of times. Allows the use of the --limit option. Useful for limiting logging rules.
   --limit - The maximum matching rate, given as a number followed by "/second", "/minute", "/hour", or "/day" depending on how often you want the rule to match. If this option is not used and -m limit is used, the default is "3/hour".

-p - The connection protocol used.
   --dport - The destination port(s) required for this rule. A single port may be given, or a range may be given as start:end, which will match all ports from start to end, inclusive.

-j - Jump to the specified target. By default, iptables allows four targets:
        ACCEPT - Accept the packet and stop processing rules in this chain.
        REJECT - Reject the packet and notify the sender that we did so, and stop processing rules in this chain.
        DROP - Silently ignore the packet, and stop processing rules in this chain.
        LOG - Log the packet, and continue processing more rules in this chain. Allows the use of the --log-prefix and --log-level options.
--log-prefix - When logging, put this text before the log message. Use double quotes around the text to use.

--log-level - Log using the specified syslog level. 7 is a good choice unless you specifically need something else.

-i - Only match if the packet is coming in on the specified interface.

-I - Inserts a rule. Takes two options, the chain to insert the rule into, and the rule number it should be.
     -I INPUT 5 would insert the rule into the INPUT chain and make it the 5th rule in the list.

-v - Display more information in the output. Useful for if you have rules that look similar without using -v.

-s --source - address[/mask] source specification

-d --destination - address[/mask] destination specification

-o --out-interface - output name[+] network interface name ([+] for wildcard)

Allowing connections

We want to use some standard rules for general network traffic. The 3 way handshake between two hosts when transmitting data.

  • NEW => Server1 connects to Server2 issuing a SYN (Synchronize) packet.
  • RELATED => Server 2 receives the SYN packet, and then responds with a SYN-ACK (Synchronize Acknowledgment) packet.
  • ESTABLISHED => Server 1 receives the SYN-ACK packet and then responds with the final ACK (Acknowledgment) packet.
After this 3 way handshake is complete, the traffic is now ESTABLISHED. In order for this type of TCP communication, something similar to these three rules are necessary:

# iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
# iptables -A FORWARD -i eth0 -m state --state RELATED,ESTABLISHED -j ACCEPT
# iptables -A OUTPUT -m state --state NEW,RELATED,ESTABLISHED -j ACCEPT

The last rule obviously allows any traffic the leave the server.

Now that we have our basics set in place, lets see what iptables lists for our rulesets:
# iptables --list
Chain INPUT (policy ACCEPT) target prot opt source destination
ACCEPT all -- anywhere anywhere state RELATED,ESTABLISHED

Chain FORWARD (policy ACCEPT) target prot opt source destination
ACCEPT all -- anywhere anywhere state RELATED,ESTABLISHED

Chain OUTPUT (policy ACCEPT) target prot opt source destination
ACCEPT all -- anywhere anywhere state NEW,RELATED,ESTABLISHED

Allowing Incoming Traffic on Specific Ports
You could start by blocking traffic, but you might be working over SSH, where you would need to allow SSH before blocking everything else.

To allow incoming traffic on the default SSH port (22), you could tell iptables to allow all TCP traffic on that port to come in.

# iptables -A INPUT -p tcp --dport ssh -j ACCEPT

Referring back to the list above, you can see that this tells iptables:
• append this rule to the input chain (-A INPUT) so we look at incoming traffic
• check to see if it is TCP (-p tcp).
• if so, check to see if the input goes to the SSH port (--dport ssh).
• if so, accept the input (-j ACCEPT).

Lets check the rules: (only the first few lines shown, you will see more)

# iptables -L
Chain INPUT (policy ACCEPT) target prot opt source destination
ACCEPT all -- anywhere anywhere state RELATED,ESTABLISHED
ACCEPT tcp -- anywhere anywhere tcp dpt:ssh

Allow all incoming web traffic
# iptables -A INPUT -p tcp --dport 80 -j ACCEPT

Checking our rules, we have 

# iptables -L
Chain INPUT (policy ACCEPT)target prot opt source destination
ACCEPT all -- anywhere anywhere state RELATED,ESTABLISHED
ACCEPT tcp -- anywhere anywhere tcp dpt:ssh
ACCEPT tcp -- anywhere anywhere tcp dpt:www

Some more ruleset for iptables, For easy understanding

Individual REJECTS First:

BAD GUYS (Block Source IP Address):
# iptables -A INPUT -s -j DROP

NO SPAMMERS (notice the use of FQDN):
# iptables -A INPUT -s -d -p tcp --dport 25 -j REJECT

Then Open it up

MYSQL (Allow Remote Access To Particular IP):
# iptables -A INPUT -s -d -p tcp --dport 3306 -j ACCEPT

# iptables -A INPUT -d -p tcp --dport 22 -j ACCEPT

# iptables -A INPUT -d -p tcp --dport 25 -j ACCEPT

FTP: (Notice how you can specify a range of ports 20-21)
# iptables -A INPUT -d -p tcp --dport 20:21 -j ACCEPT

Passive FTP Ports Maybe: (Again, specifying ports 50000 through 50050 in one rule)
# iptables -A INPUT -d -p tcp --dport 50000:50050 -j ACCEPT

# iptables -A INPUT -d -p tcp --dport 80 -j ACCEPT

# iptables -A INPUT -d -p tcp --dport 443 -j ACCEPT

# iptables -A INPUT -d -p tcp --dport 143 -j ACCEPT

# iptables -A INPUT -d -p tcp --dport 993 -j ACCEPT

# iptables -A INPUT -d -p tcp --dport 110 -j ACCEPT

# iptables -A INPUT -d -p tcp --dport 995 -j ACCEPT

Any Traffic From Localhost:
# iptables -A INPUT -d -s -j ACCEPT

# iptables -A INPUT -d -p icmp -j ACCEPT

Global REJECTS Last:
Reject everything else to that IP:

# iptables -A INPUT -d -j REJECT

Or, reject everything else coming through to any IP:
# iptables -A INPUT -j REJECT
# iptables -A FORWARD -j REJECT

Saving rules in iptables

For save active rules:
# /etc/init.d/iptables save This will save rules to '/etc/sysconfig/iptables'.

If start iptables, the rules are read from '/etc/sysconfig/iptables'
# /etc/init.d/iptables startStarting iptables [OK]

If you stop iptables, all rules are flushed
# /etc/init.d/iptables stopStopping iptables [OK]

Export and importing rulesets to file

# iptables-save > /root/iptables-save.out This will save rules to iptables-save.out file

# iptables-restore -c /root/iptables-save.out
The -c tells iptables-restore that this is file was created using iptables-save to ruleset.

This is a basic tutorial about iptables. We can do lot of things by iptables. I hope good practice on iptables only give better knowledge. Keep practicing.

      Reference : Lot of articles from internet. Thanks to all. 

Tuesday, March 29, 2011

SNMP - Simple Network Management Protocol

SNMP (Simple Network Management Protocol) is the protocol , that can be used for monitoring and managing hosts in network. Network may be LAN or WAN whatever. Hosts may be routers, switches, servers, workstations, printers, modem and more. Every hosts under network will be monitoring and managing by SNMP. SNMP have 3 main parts. Those are
  • Managed device
  • Agent - Software which runs on managed devices
  • Network management system (NMS) — Software which runs on the manager
Managed Device :
   The managed device is normally a host in network(or network elements). As above it may be router,switch, client computer, server etc. It implements an SNMP interface that allows unidirectional (read-only) or bidirectional (read and write) access to node-specific information. Managed devices exchange node-specific information with the NMSs.

   Agent is a software running in Managed device. This software act as an agent. That means, software will get the information about managed device and send it to NMS. The information is related with software, hardware installed in managed device, network traffic and related information. We can tell that information as log. Depend upon the agent, our work maybe monitoring or managing. If we have read access to the managed device via agent, we can do the monitoring alone. If we have write access to the managed device we can do the managing operation.

NMS (Network Management System) is combination of manager system ( mostly server) and software of managing. ( It's not like agent). It executes applications that monitor and control managed devices. NMSs require bulk amount of the processing and memory resources. One or more NMSs may exist on any managed network.

Management Information base (MIB)
MIB is a virtual database used for managing the entities in a communications network. Most often associated with the Simple Network Management Protocol (SNMP), the term is also used more generically in contexts such as in OSI/ISO Network management model. While intended to refer to the complete collection of management information available on an entity, it is often used to refer to a particular subset, more correctly referred to as MIB-module. MIBs use the notation defined by ASN.1

Note: Abstract Syntax Notation One (ASN.1) is a standard and flexible notation that describes data structures for representing, encoding, transmitting, and decoding data. It provides a set of formal rules for describing the structure of objects that are independent of machine-specific encoding techniques and is a precise, formal notation that removes ambiguities.

Protocol details
SNMP operates in the Application Layer of the Internet Protocol Suite (Layer 7 of the OSI model). The SNMP agent receives requests on UDP port 161. The manager may send requests from any available source port to port 161 in the agent. The agent response will be sent back to the source port on the manager. The manager receives notifications (Traps and InformRequests) on port 162. The agent may generate notifications from any available port.

SNMPv1 specifies five core protocol data units (PDUs). Two other PDUs, GetBulkRequest and InformRequest were added in SNMPv2 and carried over to SNMPv3.All SNMP PDUs are constructed as follows:
IP headerUDP headerversioncommunityPDU-typerequest-iderror-statuserror-indexvariable bindings

The seven SNMP protocol data units (PDUs) are as follows:

A manager-to-agent request to retrieve the value of a variable or list of variables. Desired variables are specified in variable bindings (values are not used). Retrieval of the specified variable values is to be done as an atomic operation by the agent. A Response with current values is returned.

A manager-to-agent request to change the value of a variable or list of variables. Variable bindings are specified in the body of the request. Changes to all specified variables are to be made as an atomic operation by the agent. A Response with (current) new values for the variables is returned.

A manager-to-agent request to discover available variables and their values. Returns a Response with variable binding for the lexicographically next variable in the MIB. The entire MIB of an agent can be walked by iterative application of GetNextRequest starting at OID 0. Rows of a table can be read by specifying column OIDs in the variable bindings of the request.

Optimized version of GetNextRequest. A manager-to-agent request for multiple iterations of GetNextRequest. Returns a Response with multiple variable bindings walked from the variable binding or bindings in the request. PDU specific non-repeaters and max-repetitions fields are used to control response behavior. GetBulkRequest was introduced in SNMPv2.

Returns variable bindings and acknowledgement from agent to manager for GetRequest, SetRequest, GetNextRequest, GetBulkRequest and InformRequest. Error reporting is provided by error-status and error-index fields. Although it was used as a response to both gets and sets, this PDU was called GetResponse in SNMPv1.

Asynchronous notification from agent to manager. Includes current sysUpTime value, an OID identifying the type of trap and optional variable bindings. Destination addressing for traps is determined in an application-specific manner typically through trap configuration variables in the MIB. The format of the trap message was changed in SNMPv2 and the PDU was renamed SNMPv2-Trap.

Acknowledged asynchronous notification from manager to manager. This PDU uses the same format as the SNMPv2 version of Trap. Manager-to-manager notifications were already possible in SNMPv1 (using a Trap), but as SNMP commonly runs over UDP where delivery is not assured and dropped packets are not reported, delivery of a Trap was not guaranteed. InformRequest fixes this by sending back an acknowledgement on receipt. Receiver replies with Response parroting all information in the InformRequest. This PDU was introduced in SNMPv2.

Reference :

Saturday, January 29, 2011

Download Mobile applications to your PC

We can't download some mobile applications to pc,

ex : gmail

Why want to download those applications to PC ,
  1. We can access applications from memory card
  2. If you move applications from phone memory to memory card also it'll work, but once u removed your memory card, it won't work.

Here the trick to download those type of applications to PC...

It's very simple.

Step 1 : First download that application to your mobile by gprs,
Step 2 : Move downloaded application from phone memory to memory card.
Step 3 : By use of data cable or blue tooth, open your memory card as mass storage in pc.
Step 4 : Open application location, there you can find .jad and .jar file (ex: application_name.jad)
Step 5 : Open .jad file using text editor, there you can find a location of .jar on internet server.
Step 6 : Before URL you can find "MIDlet-Jar-URL:"
Step 7 : Copy that link location and past it to your pc browser, and hit enter.
Step 8 : Download will start, then you can copy that file to mobile and can use. :-)

Steps for download GMail mobile application from

Go to and use faster gmail, download gmail application to mobile ( mostly it store in phone memory).

Move phone memory to memory card.

Copy .jad file from mobile memory to pc

Open  .jad on notepad. find line,
Underlined link may be change, Copy that line to browser and download file.

Copy to memory card and use.

* U can use this link for download .jar file, But there is chance, that application not to work. So do all steps.

Drawback : Can't update application.
My Mobile : Nokia 6303i classic

Tuesday, January 18, 2011

Learning MySQL on linux - Installation

MySQL on Linux

MySQL - Installation 

Installing mysql on Redhat is very simple wia repostory also packages are avaliable in redhat dvd itself. For more information click, dvd repository and rpm forge. For detailed installation about MySQL with all systems check this page.

Normaly MySQL having 2 parts,
  • MySQL Server
  • MySQL Client
MySQL server -  It's program to managing storage of data

MySQL Client - It's a program for user intraction and we can get stored data by queries. 

Installing MySQL with repository

Open terminal window and in root account, run following comment

#yum install mysql*

type y and hit enter, this will install MySQL on your redhat system.

For start MySQL,

in terminal type " service mysqld start " without cotes.

For check status of MySQL running on your linux box, in terminal type "service mysqld status " without cotes.

Login in to MySQL on linux box,

In terminal window, type

#mysql -u root mysql

and hit enter, you get a mysql prompt as follow,

In mysql -u root mysql,

mysql :
mysql -u root mysql

highlighted 'mysql' will start mysql client for user intraction.

-u :
mysql -u root mysql

highlighted '-u' says to MySQL chient which user want to login into MySQL server.

root :
mysql -u root mysql

highlighted 'root' mentioning mysql should login as root user. (It's not linux root user, It's root user of MySQL server). It gives full control of MySQL server.

mysql -u root mysql
highlighted 'mysql' is a database, this database in by default in MySQL server. It have several table.

Set password for MySQL user:

type following command after login in to mysql server,

mysql>SET PASSWORD FOR root@localhost=PASSWORD('rootpass');


SET PASSWORD FOR root@localhost=PASSWORD('rootpass');

highlighted things are queries,

root@localhost, is user name with host address ,

rootpass is password for root login.

Learning MySQL on linux - Introduction

MySQL on Linux

MySQL - Introduction

MySQL is a relational database management system (RDBMS).

The Database is a system for store, organize and retrieve large amount of data fast and easily. It have a collection of data for multiple uses in digital form.

A Database Management System (DBMS) is a set of computer programs that controls the creation, maintenance, and the use of a database. A DBMS is a system software package that helps the use of integrated collection of data records and files known as databases. It allows different user application programs to easily access the same database. In large systems, a DBMS allows users and other software to store and retrieve data in a structured way. Instead of having to write computer programs to extract information, user can ask simple questions in a query language. DBMSs may use any of a variety of database models, such as the network model or relational model.

A Database model is the theoretical foundation of a database and fundamentally determines in which manner data can be stored, organized and manipulated in a database system. It thereby defines the infrastructure offered by a particular database system. The most popular example of a database model is the relational model.

  • Hierarchical model
  • Network model
  • Relational model
  • Entity-relationship
  • Object-relational model
  • Object model

The relational model for database management is a database model based on first-order predicate logic, first formulated and proposed in 1969 by E.F. Codd.

A relational database management system (RDBMS) is a database management system (DBMS) that is based on the relational model as introduced by E. F. Codd. Most popular commercial and open source databases currently in use are based on the relational database model.
A short definition of an RDBMS may be a DBMS in which data is stored in the form of tables and the relationship among the data is also stored in the form of tables.
SQL - Structured Query Language is database computer language designed for managing data in Relational database management system. ( Developed by IDM )

MySQL - is a relational database management system (RDBMS) that runs as a server providing multi-user access to a number of databases. The MySQL development project has made its source code available under the terms of the GNU General Public License, as well as under a variety of proprietary agreements. MySQL was owned and sponsored by a single for-profit firm, the Swedish company MySQL AB, now owned by Oracle Corporation.

Difference between SQL & MySQL

SQL (Structured Query Language) is computer language that can be used to access data stored in relational databases.  SQL is not itself a standalone computer application, but is part of many relational Database programs like MySQL, Oracle, Sybase, Microsoft SQL Server, etc.

MySQL is open source database management system. It's an application. It've SQL interpreter, a database manager component, GUI database viewers, and session monitoring tools, etc. MySQL is a multithreaded, multi-user SQL database management system (DBMS) providing multi-user access to a number of databases. 

The difference between SQL and MySQL are like, difference between HTML and Dreamweaver. HTML is webpages standard, dreamweaver is computer application that can be used to create, edit webpages.

Reference : Wikipedia and some websites on Internet.

Saturday, January 1, 2011

Happy New Year - 2011


Every tool is a weapon 
If you hold it right
- Ani DiFranco

I wish you this Y2K-XI will give all Goodness to You
Your family ever...

Kumar P