manage chain:
# iptables -N new_chain				// create a chain
# iptables -E new_chain old_chain  		// edit a chain
# iptables -X old_chain				// delete a chain

redirecting packet to a user chain:
# iptables -A INPUT -p icmp -j new_chain

listing rules:
# iptables -L					// list all rules of all tables
# iptables -L -v				// display rules and their counters
# iptables -L -t nat				// display rules for a specific tables
# iptables -L -n --line-numbers			// listing rules with line number for all tables
# iptables -L INPUT -n --line-numbers		// listing rules with line number for specific table

manage rules:
# iptables -A chain				// append rules to the bottom of the chain
# iptables -I chain [rulenum]			// insert in chain as rulenum (default at the top or 1)
# iptables -R chain rulenum			// replace rules with rules specified for the rulnum
# iptables -D chain	rulenum			// delete rules matching rulenum (default 1)
# iptables -D chain				// delete matching rules

change default policy:
# iptables -P chain target			// change policy on chain to target
# iptables -P INPUT DROP			// change INPUT table policy to DROP
# iptables -P OUTPUT DROP			// change OUTPUT chain policy to DROP
# iptables -P FORWARD DROP			// change FORWARD chain policy to DROP

More Photos: http://www.flickr.com/photos/raynux/tags/mac4lin/

File: RayInstall.sh

# RayInstall.sh
#
# Ubuntu Intrepid & Hardy
#
# A very simple Bash Script file to automate installation of necessary
# softwares for PHP-MySQL development and desktop uses in a ubuntu box
#
# This may take several hours or even days depending on your internet connection speed.
#	It tooks 8 Hours for me with about 70-130 KBps of speed
#
# @uses Aplication -> Accesories -> Terminal
#		Now write following command "sudo sh ./RayInstall.sh" without quotes
#		and press enter button on your keyboard
#
# @author ray@raynuxcom
# @licence GPL

#
# For PHP-MySQL Based Development
#

# Install Apache version 2 web server
apt-get -y install apache2 apache2-doc

# Install PHP with necessary modules
apt-get -y install php5 libapache2-mod-php5 php5-cli
apt-get -y install php5-curl php5-dev php5-gd php5-gmp php5-imap php5-ldap php5-mcrypt php5-mhash php5-ming php5-odbc php5-pspell php5-snmp php5-sybase php5-tidy curl libwww-perl imagemagick

# Install MySQL Database server
apt-get -y install mysql-server php5-mysql mysql-gui-tools-common

#Restart apache
/etc/init.d/apache2 restart

# Install Webmin, A web based frontend for linux box.
apt-get -y install webmin

# Install Subversion & Rapidsvn a subversion gui client tools
apt-get -y install subversion subversion-tools libapache2-svn
apt-get -y install rapidsvn

#Restart apache
/etc/init.d/apache2 restart

#Install Doxygen, An documentation tools for PHP Application
apt-get -y install doxygen doxygen-gui doxygen-doc graphviz

# Install Phpmyadmin, A web based mysql administration tools
apt-get -y install phpmyadmin

# Install Java runtime for Eclipse PDT to work properly
apt-get -y install sun-java6-bin sun-java6-jdk sun-java6-jre

# Install Eclipse PDT
# Just download the pdt-all-in-one peckage from zend site
# http://downloads.zend.com/pdt/all-in-one/pdt-1.0.3.R20080603_debugger-5.2.14.v20080602-all-in-one-linux-gtk.tar.gz
# Unpack it in a suitable location.
# run eclipse/eclipse from the unpacked folder and you are done
# Now install Subclipse plugin using eclipse update tools

#
# Graphics, 2D and 3D Modeling Softwares & tools
#

# Install inkscape, An Illustrator alternative
apt-get -y install inkscape

# Install dia and graphical UML modeling tools
apt-get -y install dia

# Install Scribus, An alternative to Adobe Pagemaker
apt-get -y install scribus

# Install Cheese,  Webcam Software, a video and photo shoot application with cool effects for the GNOME desktop
apt-get -y install webcam cheese

# Install QCAD, and linux alternative to CAD Program.
apt-get -y install qcad

# Install Blender, Linux alternative for 3D Modeling
apt-get -y install blender

#
# Misc. Tools
#

# Install Wine, to run windows program
apt-get -y install wine

# Install XChm to read CHM Help file and Manual
apt-get -y install xchm

#
# Multimedia Players and codec
#

# Install GStreamer restricted codec to run mp3 and other media file
apt-get -y install gstreamer0.10-plugins-ugly gstreamer0.10-plugins-bad

# XMMS2 Media player
apt-get -y install xmms2 gxmms2

# Install vlc player, An alternative media player. Can play DVD file with title
apt-get -y install vlc vlc-plugin-*

# Install Amarok music player
apt-get -y install amarok

# Install k3b, A dvd burner application
apt-get -y install k3b

#
# Network and internet tools
#

# Install OpenSSH server to access your ubuntu box remotely
apt-get -y install openssh-server openssh-client

#Install gnome-network-admin, not available in default ubuntu 8.10
apt-get -y install gnome-network-admin

# Install Webhttrack, Website copier tools for linux
apt-get -y install webhttrack

# Install kopete instant messenger
apt-get -y install kopete

# install Internet Explorer in Ubuntu (Experimental)
apt-get -y install wine cabextract msttcorefonts

#run the following command manually to install IE
# wget http://www.tatanka.com.br/ies4linux/downloads/ies4linux-latest.tar.gz
# tar zxvf ies4linux-latest.tar.gz
# cd ies4linux-*
# ./ies4linux

If you are using Ubuntu on your computer and want to automate the installation process utilising this script then perform the following steps:

• Create a file name RayInstall.sh in you home folder.
• Copy and paste the above code inside the the file and save it.
• Open a terminal window from Applications -> Accessories -> Terminal
• Write the following command
• sudo sh ./RayInstall.sh
• press Enter
• Now it will start installing all the softwares listed in the script and you may need to provide some information during installation process when needed.

This script may be helpful for newbies. If you have any comment or suggestion regarding this script please let me know as I am also a newbie in Ubuntu.

In both Fedora and Ubuntu this task includes two basic steps. These are:

• Enter into your existing hard disk linux system.
• Setup GRUB Boot Loader using GRUB program.

a. Enter into your existing hard disk linux system.

Fedora 7:

In fedora recovering grub is easy task as fedora automatically mount the existing system image to /mnt/sysimage in rescue mode.

1. Insert the fedora installation cd to boot from cd.
2. When the boot menu appear enter the rescue mode. A message will be prompt saying mounting the existing fedora system on /mnt/sysimage, click ok.
3. In rescue mode you will be in a shell
4. Enter the following command
   #chroot /mnt/sysimage
5. Now you are in your existing fedora operating system.

Ubuntu 8.04 LTS:

In ubuntu you will have to mount the existing system image manually.

1. Insert the ubuntu live cd and start a live session from cd.
2. open the terminal window
3. the following command will display currently mounted device or harddisk partitions
   #df -h
4. get the device name for /boot if exists or / (root) partition say /dev/sda9.
5. enter the following command
   #sudo mkdir ubuntu
#sudo mount -t ext3 /dev/sda9 ubuntu
6. If you have separate /usr partition say /dev/sda7 enter the following command too.
   #sudo mount -t ext3 /dev/sda7 ubuntu/usr

7. Enter the following command to mount /proc and /dev and change chroot.
   #sudo mount -t proc none ubuntu/proc
#sudo mount -o bind /dev/ ubuntu/dev
#sudo chroot ubuntu /bin/bash
8. Now you are in your existing ubuntu operating system.

b. Setup GRUB Boot Loader using GRUB program.

In grub you are mainly required to find the boot device and set the root to bood device.

1. Insert the ubuntu live cd and start a live session from cd.
   #grub
2. Find the existing boot device using following command. Which will out put something like (hd0,0) or (hd0,5) say (hdX,Y).
   #grub> find /boot/grub/stage1
3. Use the above output in the following two commands.
   #grub> root (hdX,Y)
#grub> setup (hdX)
#grub> quit
4. if everything is ok then you are done. just reboot the system.

This article is completely based on my current experience and I am still a newbie in linux environment. so there may have sevaral other options to do the same task.