Saturday, June 30, 2007

Anatomy of the Linux networking stack.

One of the greatest features of the Linux® operating system is its networking stack. It was initially a derivative of the BSD stack and is well organized with a clean set of interfaces. Its interfaces range from the protocol agnostics, such as the common sockets layer interface or the device layer, to the specific interfaces of the individual networking protocols. This article explores the structure of the Linux networking stack from the perspective of its layers and also examines some of its major structures.

Thursday, June 28, 2007

Speaking UNIX: Ramble around the UNIX file system

Many directories in the UNIX® file system serve a special purpose, and certain directories are named per long-standing convention. In this installment of the "Speaking UNIX" series, discover where UNIX stores important files.
I just purchased a Global Positioning System (GPS) navigation device and, after only a handful of uses, I'm hooked. Getting from Point A to Point B is now a snap. No more MapQuest. No more guessing which way is east. No more pit stops in the sticks to ask for clarifications. I simply jump in my car, specify my destination, and follow the voice prompts. Why, the GPS makes me look like a local, giving new meaning to the Buckaroo Banzai maxim, "Wherever you go, there you are."
read more

Monday, June 25, 2007

Four ways to hide information inside image and sound objects.

Ever find yourself with too many passwords to remember and no idea where to keep them so that only you can find the password list? Creating a password.txt file in your root directory is out of the question, as is a password-protected file. A piece of paper hidden somewhere is not a good idea, because after you forget where did you put it, someone else will find it and abuse it. Instead of these approaches, consider using steganography, a method for hiding sensitive information inside some other object, typically a JPEG picture or a sound file, read more

Red Hat Linux awarded top government security rating.

June 15, 2007 (IDG News Service) -- Red Hat Linux has received a new level of security certification, one that should make the software more appealing to some government agencies.

Last week IBM Corp. was able to achieve EAL4 Augmented with ALC_FLR.3 certification for Red Hat Enterprise Linux, putting it on a par with Sun Microsystems Inc.'s Trusted Solaris operating system, said Dan Frye, vice president of open systems with IBM , read more

Sunday, June 24, 2007

VectorLinux SOHO: A better Slackware than Slackware.

VectorLinux has been one of my favorite projects since my first test of the distribution almost 18 months ago. I like VectorLinux because its roots are firmly planted in the stability and simplicity of Slackware, yet it comes with an extensive software base and lots of out-of-the-box great looks; in other words, a rock solid foundation with eye candy and useful functionality. While standard VectorLinux comes with the Xfce desktop environment and a variety of general-purpose applications, VectorLinux 5.8 SOHO offers the KDE desktop and a host of applications for small and home office more.

Saturday, June 23, 2007

Develop with Java and PHP technology on AIX Version 5.3, Part 2: Building the Java business application.

It is possible to develop applications that employ both Java™ and PHP technology. You can use Java technology for the core logic (or redeploy an existing Java-based application), while gaining the benefits of PHP as a Web-based interface platform. In this tutorial, the second part of a six-part series, create a simple Java business application and then deploy it as a servlet on the Apache Tomcat application server on a System p™ system with the IBM AIX® Version 5.3 operating system.

Wednesday, June 20, 2007

A different flavor of BSD -- 24-hour test drive: PC-BSD.

PC-BSD is not a Linux distribution, but rather it could be considered among the first major FreeBSD-based distributions to live outside of the official FreeBSD. Like most distributions, it has implemented certain features in a way that attempts to distinguish it from the competition, and I will focus mostly on these differences. This test drive is intended to give an overview of what PC-BSD is and why one would consider using it.

Monday, June 18, 2007

Working on UNIX through your laptop.

I use cygwin to open up terminals from my Windows laptop to my IBM p270 workstation (running AIX 5.1 ML3) when I want to stay in the same windowing environment for both. The following procedure will work on any flavor of Unix that uses terminfo terminal more

Sunday, June 17, 2007

Hone your regexp pattern-building skills, Handy regular expressions for system administration

Add to your bag of tricks several handy techniques for crafting real-world regular expressions (regexps). Building regexps is a part of the daily life of any administrator. Learning to think in terms of pattern matching, in order to construct successful regexps that return the desired criteria, is a skill that takes both time and practice. more

Know your regular expressions. Essential aids in building and testing regular expressions on UNIX systems.

You can build and test regular expressions (regexps) on UNIX® systems in several ways. Discover the available tools and techniques that can help you learn how to construct regular expressions for various programs and languages. read more

Thursday, June 14, 2007

Solving coding problems with temporary variables when porting applications from Solaris to AIX.

Need to port Solaris applications to AIX? This article focuses on the differences between AIX and Solaris when using temporary variables

Wednesday, June 13, 2007

Linux tip: Bash parameters and parameter expansions.

Do you sometimes wonder how to use parameters with your scripts, and how to pass them to internal functions or other scripts? Do you need to do simple validity tests on parameters or options, or perform simple extraction and replacement operations on the parameter strings? This tip helps you with parameter use and the various parameter expansions available in the bash shell.

Sunday, June 10, 2007

Port your code around the world with m17n.

To make Linux® applications usable worldwide, with no inequity between Western dialects and the rest of the world's many languages, you must be able to deliver localized versions that input, store, retrieve, and render any language, no matter how complex. The multilingualization library, or m17n, provides a single internationalization solution for all languages on UNIX®-like platforms. read more

Saturday, June 09, 2007

Second Life client, Part 1: Hacking Second Life.

The open source release of the Second Life viewer program by developer Linden Lab offers a rare opportunity to peer into the comparative strengths of closed and open source development models. This article, the first in a series, gives an overview of some of the differences between these development styles, and talks about what's involved in setting up your own build environment.

Thursday, June 07, 2007

Virtual Linux.

Virtualization means many things to many people. A big focus of virtualization currently is server virtualization, or the hosting of multiple independent operating systems on a single host computer. This article explores the ideas behind virtualization and then discusses some of the many ways to implement virtualization. We also look at some of the other virtualization technologies out there, such as operating system virtualization on Linux.
To virtualize means to take something of one form and make it appear to be another form. Virtualizing a computer means to make it appear to be multiple computers or a different computer entirely.

Virtualization also can mean making many computers appear to be a single computer. This is more commonly called server aggregation or grid computing.

Let's begin with the origins of more

Anatomy of the Linux kernel.

The Linux® kernel is the core of a large and complex operating system, and while it's huge, it is well organized in terms of subsystems and layers. In this article, you explore the general structure of the Linux kernel and get to know its major subsystems and core interfaces. Where possible, you get links to other IBM articles to help you dig deeper.
Given that the goal of this article is to introduce you to the Linux kernel and explore its architecture and major components, let's start with a short tour of Linux kernel history, then look at the Linux kernel architecture from 30,000 feet, and, finally, examine its major subsystems. The Linux kernel is over six million lines of code, so this introduction is not exhaustive. Use the pointers to more content to dig in further

Wednesday, June 06, 2007

i5/OS Information Center.

Your source for technical information about IBM(R) System i5(TM), eServer(TM) i5, and eServer iSeries(TM). check it out.

Open BIOSes for Linux.

On many systems, a large portion of boot time goes into providing legacy support for MS-DOS. Various projects, including LinuxBIOS and Open Firmware, are trying to replace the proprietary BIOS systems with streamlined pieces of code able to do only what is necessary to get a Linux® kernel loaded and running. This article gives a brief overview of the field.

Industrial-strength Linux lockdown, Part 1: Removing the shell.

For technical and non-technical users alike, maintaining a large installed base of Linux machines can be a harrowing experience for an administrator. Technical users take advantage of Linux®'s extreme configurability to change everything to their liking, while non-technical users running amok within their own file systems. This tutorial is the first in a two-part series that shows you how and why to lock those machines down to streamline the associated support and administration processes. In this tutorial, you learn how to remove the interpreters from the installation base system.

Tuesday, June 05, 2007

The Perfect Server - CentOS 4.5 (32-bit).

This tutorial shows how to set up a CentOS 4.5 server that offers all services needed by ISPs and web hosters: Apache web server (SSL-capable), Postfix mail server with SMTP-AUTH and TLS, BIND DNS server, Proftpd FTP server, MySQL server, Dovecot POP3/IMAP, Quota, Firewall, etc. This tutorial is written for the 32-bit version of CentOS 4.5, but should apply to the 64-bit version with very little modifications as well.

Monday, June 04, 2007

Writing AIX kernel extensions.

Learn how to use the AIX kernel to build routines to extend functions and create your own system calls, kernel processes, or file systems. The rapid improvements in Power architecture, combined with the enhancements of AIX® Version 5.3, have caused more interest than ever in AIX. This article shows you, with extensive examples, how to tap into the power of kernel extensions on AIX. more

Sunday, June 03, 2007

How-To: Recover root password under linux with single user mode.

It happens sometime that you can't remember root password. On Linux, recovering root password can be done by booting Linux under a specific mode: single user mode.
This tutorial will show how to boot Linux in single user mode when using GRUB and finally how to change root password.

During normal usage, a Linux OS runs under runlevels between 2 and 5 which corresponds to various multi-user modes. Booting Linux under runlevel 1 will allow one to enter into a specific mode, single user mode. Under such a level, you directly get a root prompt. From there, changing root password is a piece of cake. read more

How-To set up a LDAP server and its clients.

LDAP (Lightweight Directory Access Protocol) allows central user, group, domain..... authentication, information storage ...

Using LDAP in a local network, you can allow your users to login and authenticate from anywhere on your network.

This tutorial will be split in 2 parts. In the first part, I will explain how-to install, configure the LDAP server, add a few users and group, in the second part, we will set up Linux client to authenticate through LDAP if the user does not exist on the local filesystem.

Saturday, June 02, 2007

Six ways to write more comprehensible code.

As a developer, time is your most valuable resource. These six tips on how to write maintainable code are guaranteed to save you time and frustration: one minute spent writing comments can save you an hour of anguish.
I learned to write, clear, maintainable code the hard way. For the last twelve years, I've made my living writing computer games and selling them over the Net using the marketing technique that was once charmingly known as shareware. What this means is that I start with a blank screen, start coding, and, a few tens of thousands of lines of code later, I have something to sell. readmore

Take a closer look at OpenBSD.

OpenBSD is quite possibly the most secure operating system on the planet. Every step of the development process focuses on building a secure, open, and free platform. UNIX® and Linux® administrators take note: Without realizing it, you probably use tools ported from OpenBSD every day. Maybe it's time to give the whole operating system a closer look. read more