WARNING: This tutorial only works with older Linux kernels version such as 2.6.xx.

A typical question from my mailbag:

How do I find out if a given PCI hardware is supported of by the current CentOS / Debian / RHEL / Fedora Linux kernel?

You can easily find out find out if a given piece of PCI hardware such as RAID, network, sound, graphics card is supported or not by the current Linux kernel using the following utilities under any Linux distributions.
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The Blue Screen of Death (BSoD) is used by Microsoft Windows, after encountering a critical system error. Linux / UNIX like operating system may get a kernel panic. It is just like BSoD. The BSoD and a kernel panic generated using a Machine Check Exception (MCE). MCE is nothing but feature of AMD / Intel 64 bit systems which is used to detect an unrecoverable hardware problem. MCE can detect:

• Communication error between CPU and motherboard.
• Memory error – ECC problems.
• CPU cache errors and so on.

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Linux kernel is the central component of Linux operating systems. It is responsible for managing the system’s resources, the communication between hardware and software and security. Kernel play a critical role in supporting security at higher levels. Unfortunately, stock kernel is not secured out of box. There are some important Linux kernel patches to secure your box. They differ significantly in how they are administered and how they integrate into the system. They also allow for easy control of access between processes and objects, processes and other processes, and objects and other objects. The following pros and cons list is based upon my personal experience.
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Geolocation software is used to get the geographic location of visitor using IP address. You can determine country, organization and guess visitors location. This is useful for

a] Fraud detection

b] Geo marketing and ad serving

c] Target content

d] Spam fighting

e] And much more.

mod_geoip is a Lighttpd module for fast ip/location lookups. In this tutorial you will learn about mod_geoip installation and php server side examples to determine visitors country.
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MAC Filtering (layer 2 address filtering) refers to a security access control methodology whereby the 48-bit address assigned to each network card is used to determine access to the network. Iptables, pf, and IPFW can block a certain MAC address on a network, just like an IP. One can deny or allow from MAC address like 00:1e:2a:47:42:8d using open source firewalls. MAC address filtering is often used to secure LAN or wireless network / devices. Is this technique effective?
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The tail command is one of the best tool to view log files in a real time using tail -f /path/to/log.file syntax on a Unix-like systems. The program MultiTail lets you view one or multiple files like the original tail program. The difference is that it creates multiple windows on your console (with ncurses). This is one of those dream come true program for UNIX sys admin job. You can browse through several log files at once and do various operations like search for errors and more.
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I’ve already written about setting the MTU (Maximum Transmission Unit) under Linux including Jumbo frames (FreeBSD specific MTU information is here).

With this quick tip you can increase MTU size to get a better networking performance.
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I’ve already written about creating a partition size larger than 2TB under Linux using GNU parted command with GPT. In this tutorial, I will provide instructions for booting to a flat 2TB or larger RAID array under Linux using the GRUB boot loader.
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fold is really nifty command line utility to make a text file word wrap. This is useful for large number of text files processing. There is no need to write a perl / python code or use a word processor.

fold command syntax

fold -sw {COUNT} {input.txt} > {output.txt}

Wrap input lines in each input.txt, writing to standard output.txt.

Where,

• -s: break at spaces
• -w: {COUNT} use COUN} as WIDTH columns instead of default 80.

For example, following command will wrap input.txt at 60 width columns:
$ fold -sw 60 input.txt > output.txt

A large number of files can be processed using for shell loop:

for i in *.txt
do
  fold -sw 65 $i > $i.output
done