Basics of Firewalls in Linux

What is a Firewall?

Just as a firewall in a building attempts to prevent a fire from spreading, a computer firewall attempts to prevent malicious or unwanted software from spreading to your computer from the network.

A Firewall also helps to prevent unauthorized users from accessing your computer.

In a default Linux installation, a firewall exists between your computer or network and any untrusted networks, for example the Internet. It determines which services on your computer remote users can access. A properly configured firewall can greatly increase the security of your system.

It is strongly recommended that you configure a firewall for any system with an Internet connection properly, to secure your computer from malicious software and external attackers.

In our next post we would like to throw some light on the ways to configure a firewall on various popular flavours of Linux.

Whats My Public IP Address

Many a times we need to know the public IP (Internet Protocol) address of the machine from where you are accessing the internet, may be for seeking remote assistance or to facilitate remote login to your computer. Here, we show you your public IP  address as being detected and recorded by various sites you visit.

IP Address = 54.80.16.75

Above kind of detection is generally done by various websites to detect user locations, detecting locale-based preferences, for security logging etc also. Based upon the IP address one can locate the physical location of the computer also.

 

How to recover Linux after installing Windows in a dual boot system……

If we install any Windows Operating System (Windows XP, Windows 7 etc) on a computer already having Linux based Operating System (Ubuntu, Kubuntu, Suse etc), the system is not able to boot into Linux based OS, as Windows installers overwrite the GRUB boot loader during installation. As a result we don’t get any option to select the operating system during boot up and system boots up into Windows straight away.

This may create a lot of panic in the mind of the user as there are fears of loosing complete Linux based installations. But no need to worry as the installed Linux based system is already there. What we need to actually do is to restore the GRUB in Linux mode.

For the above problem we need to do following:

Download SuperGRUB from http://www.supergrubdisk.org/.

Burn the ISO into a CD using a CD burner tool.

Make sure your system is set up to boot from the CD (in the BIOS set up).

Reboot your computer after placing the CD so burned, into the CD tray.

The computer will boot up from CD and will load GRUB 2 and show you a screen as shown below.

grub2 screenshot

Select the option named “Detect any Operating System” using arrow keys and press enter key.

Please wait for a while, during which the superGRUB searches for the installed operating systems.

It will show up a list of all the Operating Systems installed in your computer.

Select the latest version of Linux Kernel shown from the available choices using the arrow keys and then press enter.

And you will see your system booting up into your Linux installation.

After complete loading of the Operating System you see your familiar desktop. This was all fine to boot up your system once. But to have a permanent choice of the Operating Systems we need to Install and Update the GRUB on the hard disk drive.

For this please follow the relevant instructions for your relevant distribution of Linux. For example, you may use the following link for doing the same on Ubuntu….

Update Grub