Unix News

Port Perl scripts from Solaris to Linux

2011-10-08T22:10:00.000+01:00

Although the Perl language is portable among platforms, most of the scripts used for system administration leverage platform-specific resources. And scripts meant for Solaris might use Solaris-specific pathnames and system commands that may have not equivalents on Linux®. This article gives you a roadmap for code remediation to help you port a Perl script from Solaris to Linux when direct mapping isn't available.

Learn Linux - Boot the system

2011-10-08T21:57:00.004+01:00

Learn to guide your Linux system through the boot process. You can use the material in this article to study for the LPI 101 exam for Linux system administrator certification, or just to learn about the boot process.

Fixing Unix/Linux/POSIX Filenames

2009-03-27T16:37:00.001+01:00

Traditionally, Unix/Linux/POSIX filenames can be almost any sequence of bytes, and their meaning is unassigned. The only real rules are that "/" is always the directory separator, and that filenames can't contain byte 0 (because this is the terminator). Although this is flexible, this creates many unnecessary problems. In particular, this lack of limitations makes it unnecessarily difficult to write correct programs (enabling many security flaws), makes it impossible to consistently and accurately display filenames, causes portability problems, and confuses users. more....

Linux Networking

2009-01-19T08:27:00.001+01:00

This tutorial covers TCP/IP networking and system configuration basics. Linux can support multiple network devices. The device names are numbered and begin at zero and count upwards. For example, a computer running two ethernet cards will have two devices labeled /dev/eth0 and /dev/eth1. Linux network configuration, management, monitoring and system tools are covered in this tutorial.

Hardening the Linux server

2009-01-19T08:26:00.000+01:00

Servers—whether used for testing or production—are primary targets for attackers. By taking the proper steps, you can turn a vulnerable box into a hardened server and help thwart outside attackers. Learn how to secure SSH sessions, configure firewall rules, and set up intrusion detection to alert you to any possible attacks on your GNU/Linux® server. Once you've gained a solid foundation in the basics of securing your server, you can build on this knowledge to further harden your systems.

Booting Debian in 14 seconds

2009-01-03T12:40:00.000+01:00

This article assumes that you're already familiar with things like building kernels, applying patches and so on. The target audience is the "advanced end user", and also the Debian developers responsible for the packages concerned who I hope will be motivated to incorporate some of this work.

Linux process management

2009-01-03T12:39:00.000+01:00

The creation and management of user-space processes in Linux® have many principles in common with UNIX® but also include several unique optimizations specific to Linux. Here, review the life cycle of Linux processes and explore the kernel internals for user process creation, memory management, scheduling, and death. more...

FreeBSD - Mounting Other Filesystems

2008-12-31T17:09:00.000+01:00

Anyone who has ever worked in a networked environment running different operating systems using different filesystems knows the frustration of trying to get every computer to see the data on every other computer. Even on my multi-boot test computer, NT can't see the data on my FAT32 partition, Windows 98 can't see the data on my NTFS partition, DOS can't see data on either partition -- and these operating systems are all installed on the same hard drive. more...

Perl : Creating Sets Using Bit Vectors

2008-12-31T12:27:00.000+01:00

To use bit vectors as sets we must enumerate the set members because all vectors have an inherent ordering. While performing the set operations, we won't consider the "names" of the members, but just their numbers, which refer to their bit positions in the bit vectors. more...

Perl's Sort Function

2008-12-31T12:20:00.000+01:00

Under the hood, Perl's sort() function uses the quicksort algorithm, which we'll describe later in the chapter. This is a standard sorting algorithm, provided by most operating systems as qsort(3).* In Versions 5.004_05 and higher, Perl uses its own quicksort implementation instead of the one provided by the operating system. more...

Displaying maps with OpenLayers

2008-12-27T01:02:00.000+01:00

Google Maps gives you a quick and easy way to add maps to your Web site, but when you're using Google's API, your ability to display other data is limited. If you have your own data you want to display, or data from sources other than Google, OpenLayers, an open source JavaScript library, can give you more options. read more...

CentOS Logical Volume Backup

2008-12-26T13:47:00.000+01:00

Metadata backups and archives are automatically created on every volume group and logical volume configuration change unless disabled in the lvm.conf file. By default, the metadata backup is stored in the /etc/lvm/backup file and the metadata archives are stored in the /etc/lvm/archive file.. more

The Kernel and Daemons

2008-12-20T17:48:00.000+01:00

If you have arrived at UNIX via DOS or some other personal computer operating system, you will notice some big differences. UNIX is, was, and always will be a multiuser operating system. It is a multiuser operating system even when you're the only person using it. It is a multiuser operating system even when it is running on a PC with a single keyboard. And this fact has important ramifications for everything that you do. more...

Cygwin provides a complete UNIX shellfrom awk to zcaton Windows

2008-12-20T17:47:00.000+01:00

Cygwin is a UNIX®-like environment for the Microsoft® Windows® operating system. It includes a real UNIX shell, a Portable Operating System Interface (POSIX) emulation library, and thousands of UNIX utilities ported to Windows. more..

Perl: How to Set Up a UDP Server

2008-11-23T16:00:00.002+01:00

You want to write a UDP server,
First bind to the port the server is to be contacted on. With IO::Socket, this is easily accomplished:
use IO::Socket;
$server = IO::Socket::INET->new(LocalPort => $server_port,
Proto => "udp")
or die "Couldn't be a udp server on port $server_port : $@\n"; read more..

Perl : Gathering Output from a Program

2008-11-23T15:56:00.000+01:00

The backticks are a convenient way to run other programs and gather their output. The backticks do not return until the called program exits. Perl goes to some trouble behind the scenes to collect the output, so it is inefficient to use the backticks and ignore their return value: read more...

Booting Debian in 14 seconds

2008-11-23T15:42:00.000+01:00

The AIX administrators guide to learning Linux

2008-11-23T15:39:00.000+01:00

Most system administrators planning to install Linux® on IBM® System p® eventually run into an important question: Which Linux distribution should I install? This article compares two distributions from Red Hat and Novell, and weighs the pros and cons of each. We'll discuss Linux on POWER (LoP), the history of both distributions, the relationship IBM has with them, and the factors that should go into your decision-making process. We're also going to compare and contrast what it takes to create logical volumes on SLES and RHEL.

GCC hacks in the Linux kernel

2008-11-23T15:38:00.000+01:00

GCC and Linux are a great pair. Although they are independent pieces of software, Linux is totally dependent on GCC to enable it on new architectures. Linux further exploits features in GCC, called extensions, for greater functionality and optimization. This article explores many of these important extensions and shows you how they're used within the Linux kernel.

Restoring iptables Automatically On Boot

2008-11-15T14:11:00.000+01:00

There used to be a script to do it automatically via init.d files, but now the suggested method is to use ifup.d networking scripts, which are executed on state changes of the network interfaces. So I submit here my simple script, which does the trick for me nicely.

know GCC 4

2008-11-15T14:09:00.000+01:00

In the last few years, the GNU Compiler Collection (GCC) has undergone a major transition from GCC version 3 to version 4. With GCC 4 comes a new optimization framework (and new intermediate code representation), new target and language support, and a variety of new attributes and options. Get to know the major new features and their benefits.

Linux Pipes

2008-11-03T21:55:00.000+01:00

A pipe is a communication device that permits unidirectional communication. Data written to the "write end" of the pipe is read back from the "read end." Pipes are serial devices; the data is always read from the pipe in the same order it was written. Typically, a pipe is used to communicate between two threads in a single process or between parent and child processes, more...

Perl directories

2008-10-23T20:11:00.000+01:00

To fully understand directories, you need to be acquainted with the underlying mechanics. The following explanation is slanted toward the Unix filesystem, for whose syscalls and behavior Perl's directory access routines were designed, but it is applicable to some degree to most other platforms.

Mailman and Exim4

2008-10-16T12:40:00.000+01:00

I recently installed Mailman on on my server to provide a mailing list for my extended family. While in the end, I was able to scrounge up the articles I needed by searching the web, many of them were woefully outdated. Here is a short article that pulls together my research and describes in one place what is needed to get Mailman running happily under Debian etch with Exim4.

Using cron to automate maintenance

2008-10-16T12:39:00.000+01:00

Learn how to create, schedule, and manage cron jobs and how to define timetables to control job frequency, from once per minute to once per year. Additionally, learn how to limit access to cron to prevent abuse and how to use other utilities in tandem with cron to automate common maintenance tasks. more...

Building tiny systems with embedded NetBSD

2008-09-30T12:10:00.000+01:00

NetBSD is an extremely flexible operating system that is designed to be portable across various architectures. This feature makes it attractive for embedded developers. In this article, I will demonstrate a process for creating a very small kernel that can boot, either to a shell prompt or to a login screen, more...

Linux Signals

2008-09-30T12:05:00.000+01:00

Signals are mechanisms for communicating with and manipulating processes in Linux. The topic of signals is a large one; here we discuss some of the most important signals and techniques that are used for controlling processes.
A signal is a special message sent to a process. Signals are asynchronous; when a process receives a signal, it processes the signal immediately, without finishing the current function or even the current line of code.

Debian Linux Kernel Handbook

2008-09-30T12:03:00.000+01:00

The main goal of this handbook is to serve as a single access point to all kernel-related documentation. It contains the information about the Debian packaging of Linux kernel for the Etch release of Debian (version 4.0). The latest released version is always available from http://kernel-handbook.alioth.debian.org. The work on a handbook version for Lenny (next Debian release) is currently in progress.

Upgrading a Linux Server to OpenSolaris

2008-09-27T21:14:00.001+01:00

For years I've been using various Linux distributions for my home-based server (Web, FTP, NTP (time), DNS (name), SMB and NFS (file)). I didn't use Solaris because (1) the license ued to cost $595 for commercial use and (2) it was missing many features found in Linux (mainly modern GNU/open source software). Now that OpenSolaris is available, I've decided to convert.more...

Monitor file system activity with inotify

2008-09-25T18:25:00.000+01:00

Inotify is a Linux® feature that monitors file system operations, such as read, write, and create. Inotify is reactive, surprisingly simple to use, and far more efficient than, say, busy polling from a cron job. Learn how to integrate inotify into your own applications, and discover a set of command-line tools you can use to further automate system administration.

Mastering Shells and Shell Scripting

2008-09-24T18:12:00.000+01:00

Many people use nothing but GUI tools for manipulating files, launching programs, and so on. This approach certainly has its merits—GUI tools tend to be easy to learn, and they fit the needs of some tasks, such as graphics programs, very well. There is an older method of interacting with computers, though, which still has advantages: text-based shells. They are programs that accept typed commands and respond to these commands by launching programs or performing actions.more...

Cloud computing with Linux

2008-09-17T10:14:00.000+01:00

Cloud computing and storage convert physical resources (like processors and storage) into scalable and shareable resources over the Internet (computing and storage "as a service"). Although not a new concept, virtualization makes this much more scalable and efficient through the sharing of physical systems through server virtualization. Cloud computing gives users access to massive computing and storage resources without their having to know where those resources are or how they're configured. As you might expect, Linux® plays a huge role. Discover cloud computing, and learn why there's a penguin behind that silver lining.

Gentoo Linux Kernel Guide

2008-09-17T10:12:00.001+01:00

As with everything else in Gentoo Linux, the philosophy of the Gentoo Kernel team is to give you, the user, as much freedom of choice as possible. If you take a look at the output of emerge -s sources you see a large variety of kernels to choose from. In this document, I will attempt to give you a brief rundown of the goals of each of the patch sets, which we at Gentoo design, and also explain the other kernel sources we make available to you. more..

Wireless Voice Calls Gain Encryption

2008-09-11T18:27:00.000+01:00

The RoamAnywhere router is customer-premises equipment (CPE) that extends PBX policy and dialing plans across Wi-Fi and cellular networks to smart phones running RoamAnywhere client software. It enables location-based, seamless roaming between both types of wireless networks so that sessions aren’t interrupted when mobile users cross wireless network borders.more...

More shell scripting techniques

2008-09-11T18:23:00.000+01:00

If you've worked on IBM® AIX®, another flavor of UNIX®, or Linux®, you've more than likely used the vi editor. Since its conception in 1976, vi has become a staple for anyone wanting to edit files. How could someone make a more powerful editing tool than vi, you may ask? The answer is Vim, and this article provides details on the many enhancements that have made Vim a highly used and acceptable editor in the world of UNIX and Linux.

Back Up Your Files With Areca On Fedora 9

2008-09-06T17:24:00.000+01:00

Areca is a personal file backup software developed in Java. It allows you to select files or directories to backup, filter, encrypt and compress their content, and store them on your backup location. Areca supports incremental backups and generates backup reports, which can be stored on your disk or sent by email. This guide explains how to install and use it on a Fedora 9 desktop (GNOME).

FreeBSD Porter's Handbook

2008-09-06T17:21:00.001+01:00

The FreeBSD ports collection is the way almost everyone installs applications ("ports") on FreeBSD. Like everything else about FreeBSD, it is primarily a volunteer effort. It is important to keep this in mind when reading this document.
In FreeBSD, anyone may submit a new port, or volunteer to maintain an existing port if it is unmaintained--you do not need any special commit privileges to do so.

Sun Solaris 10 on AMD

2008-08-29T14:23:00.000+01:00

With an OS long prized by government organizations like the US Navy, US Army, Air Force Research Labels, the Department of Defense and many others, Sun has listened and learned from its government customers. Solaris 10 11/06 incorporates Sun's most advanced security features to date, many of which have been optimized for AMD architecture.more...

Running MS Office and IE on Linux

2008-08-29T11:12:00.000+01:00

Wine began its life in 1993 as a way to run Windows 3.1 applications in Linux. Wine may well have had the longest beta period in history at 15 years, however version 1.0 was recently released in June 2008.
In this article, I show you how to install Wine, Microsoft Office 2003, and Internet Explorer using my Red Hat derivative system (CentOS 5.1) as the host. You can give your system some Wine by compiling from source code, or by installing pre-compiled binaries from your distro’s repositories.

LDAP Authentication In Linux

2008-08-27T15:24:00.000+01:00

This howto will show you howto store your users in LDAP and authenticate some of the services against it. I will not show howto install particular packages, as it is distribution/system dependant.

How To Set Up A Cisco Lab On Linux

2008-08-27T15:21:00.000+01:00

After a quick search I found the wonderful Dynamips project that goes beyond what other simulators do by running actual Cisco IOS images, as well as the PEMU project which allows for running of Cisco PIX images. To integrate the various pieces of software...more.

Installing A FreeBSD 7.0 DNS Server With BIND

2008-08-23T11:32:00.000+01:00

As FreeBSD is known as one of the most stable and reliable operating systems, I decided to publish some useful articles for it, mixing it with services we need on daily bases. This tutorial shows how to set up a FreeBSD based server that offers DNS services.

Connection testing with Perl

2008-08-22T04:12:00.001+01:00

The script itself uses a series of commands to set up the socket, starts to LISTEN on that socket and sends the simple "You have connected" message to systems that connect to it, read more..

Getting Started With SSH

2008-08-20T18:20:00.000+01:00

There are a few useful options you can pass to OpenSSH to increase your verbosity, compress and speed up your ssh connection, and change your SSH cipher to something faster and more secure;
'-v' switch. This option will allow you to see debug output for outgoing SSH connections. Specifying '-v' multiple times increases the verbosity level (maximum level 3).more...

Building and Installing PL/Perl

2008-08-20T18:11:00.000+01:00

If the --with-perl option was supplied to the configure script, the PostgreSQL build process will attempt to build the PL/Perl shared library and install it in the PostgreSQL library directory.
Because PL/Perl is a shared library, the libperl library must be a shared library also. A Red Hat Database installation meets these conditions; however, if you use another PostgreSQL source and have problems, more...

Gentoo Perl Herd Guide

2008-08-20T18:09:00.000+01:00

This document assumes a base understanding of general ebuild structure and techniques. For more information, please see the following link.

The new and improved Vim editor

2008-08-20T18:06:00.000+01:00

ANSI C with Unix

2008-08-16T21:00:00.000+01:00

This book is intended as a sophomore level university text book. The coverage of subject material assues that the reader has a working knowledge of higher level languages in general and is familiar with a reasonable modern program development environment. The purpose of the book is to introduce those already familiar with programming to a more system-oriented language that provides the programmer with a greater degree of freedom (and therefore responsibility).

Class::DBI Intro

2008-08-15T15:20:00.000+01:00

When working with databases there are several solutions on CPAN that deal with Object Oriented access to database tables that either avoid completely or minimize the use of SQL. Unfortunately most of these modules have a rather large learning curve, not necessarily the module itself, but all the precursors to it.more..

Solaris Network Administration Scripts

2008-08-10T16:29:00.000+01:00

Here's a little script I was working on back in the college lab last month. I was facing a very trivial solaris administration problem. I've installed SXDE 1/08 on 120 systems in one of our biggest computer labs long back (more on how I did that later). Now I needed a way to do certain tasks on each of those systems like changing the boot order, changing the solaris GRUB splash image, setting the hostname for each system based on its current IP address...,more.

10 essential tricks for admins

2008-08-10T16:26:00.000+01:00

Learn these 10 tricks and you'll be the most powerful Linux® systems administrator in the universe...well, maybe not the universe, but you will need these tips to play in the big leagues. Learn about SSH tunnels, VNC, password recovery, console spying, and more. Examples accompany each trick, so you can duplicate them on your own systems.

OpenAFS installation on Debian

2008-08-05T20:09:00.000+01:00

The purpose of this article is to give you a straight-forward, Debian-friendly way of installing and configuring OpenAFS 1.4.x, the recommended production version of OpenAFS for UNIX. By the end of this guide, you will have a functional OpenAFS installation that will complete our solution for secure, centralized network logins with shared home directories.

The importance of UNIX in SOA environments

2008-08-05T20:07:00.000+01:00

These are exciting times in solution architecture . . . that is, if you embrace the challenges of learning and implementing technologies such as Service-Oriented Architecture (SOA), Web services, mash-ups, portals, and the like. For business executives, project managers, sales execs, and various resource managers, SOA and the myriad of new tools and technologies about which you must make immediate business decisions may seem impossible to keep up with. The goal of this article is to explain how...more.

Ext2 Disk Data Structures

2008-08-02T15:55:00.000+01:00

The first block in any Ext2 partition is never managed by the Ext2 filesystem, since it is reserved for the partition boot sector (see Appendix A). The rest of the Ext2 partition is split into block groups, each of which has the layout shown in Figure 17-1. As you will notice from the figure, some data structures must fit in exactly one block, while others may require more than one block. All the block groups in the filesystem have the same size and are stored sequentially, thus the kernel can derive the location of a block group in a disk simply from its integer index. more...

What's New in FreeBSD 7.0

2008-07-27T17:12:00.001+01:00

FreeBSD is back to its incredible performance and now can take advantage of multi-core/CPUs systems very well... so well that some benchmarks on both Intel and AMD systems showed release 7.0 being faster than Linux 2.6 when running PostreSQL or MySQL,more...

AIX security commands

2008-07-27T17:09:00.000+01:00

AIX provides a vast array of commands to handle user and group management. This article discusses some of these core security commands and provides a list that you can use as a ready reference. The behavior of these commands should be identical in all releases of AIX.

How To Install Django On Debian Etch (Apache2/mod_python)

2008-07-24T11:44:00.001+01:00

This tutorial explains how to install Django on a Debian Etch server. Django is a web framework that allows to develop Python web applications quickly with as much automation as possible. I will use it with Apache2 and mod_python in this guide.

Using Software RAID-1 with FreeBSD

2008-07-23T10:55:00.000+01:00

Have you ever needed a software RAID solution for a low-end server install? Perhaps you've wanted your workstation to take advantage of the redundancy provided by a disk mirror without investing in a hardware RAID controller. Has a prior painful configuration experience turned you off software RAID altogether on Unix systems? more...

Making Computers More Human

2008-07-20T16:32:00.000+01:00

Ever wonder why your computer doesn’t give you a hug? How about a slap on the back for a job well done? Computers have evolved over time to become effective and efficient tools, even integral parts of our daily lives. Yet there is one vital component missing—the human touch. read more..

Securing Small Networks with OpenBSD

2008-07-19T22:01:00.000+01:00

Like almost all things in life, good security costs good money. It has to be that way, because there are simply not enough skilled security specialists to look after all of the networks that need their attention. An unfortunate result of low supply and high demand is the migration of highly skilled personnel to clients who can meet their salary requirements. This leaves a lot of small and underfunded networks in the hands of less experienced administrators, who might not know how to design, configure, and monitor these networks' safety mechanisms, leaving them vulnerable to attacks from unscrupulous people looking for inside information, free warez storage, zombie hosts for DDoS attacks, or systems they can simply destroy for fun of doing it,more...

Firewalling with OpenBSD's PF packet filter

2008-07-15T20:05:00.005+01:00

This lecture will be about firewalls and related functions, starting from a little theory along with a number of examples of filtering and other network traffic directing. As in any number of other endeavors, the things I discuss can be done in more than one way. Under any circumstances I will urge you to interrupt me when you need to.

Migrate device control applications from Windows to Linux

2008-07-13T11:15:00.000+01:00

If you develop device control applications on different platforms, you know that Windows and Linux have different ways of doing device control, and migrating applications from one to the other can be a pain. In this article, we analyze how device control works in both operating systems, examining everything from architecture to system calls and focusing on the differences. We also give you a migration sample (in C/C++) to demonstrate the migration in detail.

Perl's Warn and Die Signals

2008-07-09T20:34:00.000+01:00

This is a tutorial on using Perl's warn and die signals. It is based on a post I made some time ago, here, but covers more of the details and raises more of the pitfalls. In this tutorial I attempt to separate the warn and die signals from the OS signals, explain how they are used and what they can be used for, and explore the problems that can come up. At the end you will find a list of additional documents you should read. Note that I write this under the risky assumption that you are using Perl 5.6. This does not exclude you if you have an older version of Perl, as I believe everything holds for Perl 5.0 with the exception of -W and the warnings pragma

Wireless Security - Protect your wireless LAN

2008-07-09T19:27:00.000+01:00

The new standard in wireless networks--802.11g--offers speed, security, and performance. It is also the most widely employed standard in corporate internal wireless LAN networks. You can transfer data at up to 54Mbps using 802.11g (which is five times the speed of older 802.11b wireless networks). And wireless LANs provide some obvious benefits: they always provide on-network connectivity, they do not require a network cable, and they actually prove less expensive than traditional networks. Wireless networks have evolved into more affordable and logistically acceptable alternatives to wired LANs. But to take advantage of these benefits, your wireless LAN needs to be properly secured.more...

Building a Desktop Firewall

2008-07-09T19:25:00.001+01:00

Everyone knows that you should be behind a firewall whenever you go online. However, not everyone knows that it's easy to create a personal firewall for a FreeBSD (or PC-BSD or DesktopBSD) system. This article shows how even a casual home user can get a firewall up and running in about ten minutes.

HOWTO SD and MMC card readers

2008-07-08T20:24:00.000+01:00

Since kernel 2.6.17 there is support for a new type of SD/MMC card reader. I had trouble initially to get it working. It seems to be quite often in notebooks and is built by at least Texas Instruments, Ricoh and Toshiba. read more...

The Kernel and the utilities.

2008-07-06T10:54:00.003+01:00

The Unix system is itself logically divided into two pieces, the kernel and the utilities. The Kernel is the heart of the Unix system and resides in the computer's memory from the time the computer is turned on and booted until the time it is shut down. read more..

Unix tutorials

2008-07-03T20:23:00.000+01:00

These tutorials will cover some of the basic commands which are common to most of the Unix shells available and some applications. Thus, when you are finished with these tutorials, you will be able to interact with any Unix system as seamlessly as if you had a windowing system available to you.

Building a Jumpstart server

2008-07-03T19:02:00.000+01:00

There may be little that's new about using Jumpstart to install Sun servers, but setting up a new jumpstart server is something that I do rarely enough that I want to make the process simpler and more reliable.more...

Simple Perl Script To Ease Console Server Use On Linux And Unix

2008-07-01T20:47:00.000+01:00

Technically, this script could be used for any server which accepts connections over telnet (Which this script is set up to use, even though I'm pretty sure I fought the good fight arguing against it). read more..

The fork() function.

2008-06-29T12:20:00.005+01:00

The fork() function is available on all UNIX versions of Perl, as well as the VMS and OS/2 ports. Version 5.6 of Perl support fork() on Microsoft windows platforms, but not unfortunately on Macintosh.read more...

Debugging Perl

2008-06-28T10:53:00.000+01:00

The standard Perl distribution comes with a debugger, although it's really just another Perl program, perl5db.pl. Since it is just a program, I can use it as the basis for writing my own debuggers to suit my needs, or I can use the interface perl5db.pl provides to configure its actions. That's just the beginning, though. read more...

It's all about the inode - how the UNIX file system manages files

2008-06-26T09:20:00.000+01:00

Have you ever wondered what Iused and %Iused mean in UNIX® commands like df or what people are talking about when the say inode? UNIX and Linux® systems both use inodes, and IBM® AIX® is no different. Discover what an inode is and why inodes are important to UNIX, the structure of an inode, and commands for working with inodes.

Arrays and hashes only with references

2008-06-25T22:08:00.000+01:00

Always when you want hash, use curly brackets {}, always if array - square brackets []. And on one nesting level treat everything as list of scalars, nothing more, nothing less, read more...

Bash Arrays

2008-06-22T17:54:00.001+01:00

If you're used to a "standard" *NIX shell you may not be familiar with bash's array feature. Although not as powerful as similar constructs in the P languages (Perl, Python, and PHP) and others, they are often quite useful. read more...

Linux - Printing with CUPS

2008-06-21T17:03:00.001+01:00

The Common Unix Printing System (CUPS) is a modern printing subsystem for Linux and Unix that replaces the hoary old Unix line-printer protocols. It runs on Unix, Linux, Mac OS, and Mac OS X, and it serves clients on nearly any platform, including Windows. more...

Network profiles for a laptop

2008-06-21T17:01:00.000+01:00

This article explains how to configure networking in a very pleasant way, so that it works automatically wherever you go. It is adaptable to lots of uses, and may be usefull even if you don't use Wifi but connect to multiple networks. This solution has been inspired by a tutorial that can be found in the references section at the bottom of this page. It uses three tools that integrate well with the debian network configuration:

Perl - Pair Programming

2008-06-18T19:42:00.000+01:00

The last planning activity in XP is pair programming. Two programmers discuss what they are about to program. They write a unit test which is a formal specification. Only after their intention has been communicated to each other, do they begin the implementation. more..

Perl PIPES

2008-06-14T19:10:00.002+01:00

Network programming is all about interprocess communications (IPC), One process exchanges data with another. Depending on the application, the two processes may be running on the same machine, may be running on two machines on the same segment of a local area network, more...

Perl Sorting Techniques

2008-06-14T19:06:00.000+01:00

Sorting is a commonly needed operation in all kinds of programs. Luckily, for us perl programmers, perl provides a very simple yet extremely powerful mechanism to accomplish any sort you might think of. This article is about teaching the novice programmer how to sort lists of things, while showing to the more experienced folks certain techniques and ideas that could be new to them if they are migrating from a different language.

Object Databases

2008-06-12T19:33:00.000+01:00

While the methods we've seen in the previous section work very well for storing and retrieving individual objects, there are times when we want to deal with a massive collection of data with the same degree of efficiency. more...

Caches, thrashes and smashes

2008-06-08T16:04:00.000+01:00

Even as George Gilder promises the world that bandwidth will be infinite, demand for network capacity seems to increase faster than corporate networks can deliver it. Wire speed may be cheap, but running a fat and wide pipe to every user's desk is typically beyond the financial reach of most IT organizations. Network congestion and server pile-ups haven't slaked our thirst for networked data access (possibly why we've devoted the last quarter's worth of columns to NFS-related topics).. more..

Calculate network with Ipcalc

2008-06-07T19:07:00.000+01:00

Ipcalc is a simple tool to calculate network, broadcast, netmask, etc. from an IP address. It also gives the class of the IP. It might facilitate the work of network admins. read more..

Kernel Basics

2008-06-07T19:04:00.000+01:00

The kernel is a program that is loaded from disk into RAM when the computer is first turned on. It always stays in RAM, and runs until the system is turned off (or crashes). Although it's mostly written in C, some parts of the kernel were written in assembly language for efficiency reasons. User programs make use of the kernel via the system call interface, more...

Make An Iterator

2008-06-03T20:26:00.000+01:00

The purpose of this tutorial is to give a general overview of what an iterator is, why they are useful, how to build one, and things to consider to avoid common pitfalls. It is intended to give the reader enough information to begin using iterators though a certain level of understanding is assumed. The See Also section should be researched if supplemental information is needed.

smb.conf Setup

2008-06-01T21:02:00.000+01:00

Because Samba is supplied on the Red Hat Linux CD-ROM, we'll walk through a simple Samba setup using Red Hat Linux. When installing Red Hat Linux, you can select the software packages you want to load, as you can on most all UNIX variants. If you did not load Samba at the time you originally loaded the operating system, you can use a graphical RPM tool or rpm from the command line to load Samba or any other software. These tools were briefly discussed in the Chapter 10 covering System Administration.

Monitoring with Munin

2008-05-31T21:52:00.000+01:00

In this article I will describe how to install munin on 2 computers, but you can add more if you want to, this will allow us to remotely monitor system performance and activity

Configuring Infiniband for AIX

2008-05-31T21:50:00.001+01:00

Infiniband is an interconnect technology that breaks through the bandwidth and fanout limitations of PCI bus by switching from traditional shared bus architecture to a switched fabric architecture. It is a switched fabric I/O technology that ties together servers, storage devices, and network devices. Instead of sending data in parallel, which is what PCI does, Infiniband sends data in serial and can carry multiple channels of data at the same time in a multiplexing signal. more..

Learn 10 more good UNIX usage habits

2008-05-31T21:47:00.000+01:00

Bad habits are hard to break. But habits that you've just become comfortable with can be even more difficult to overcome. Sometimes, a fresh look at things may provide you with an "A-ha, I didn't know you could do that!" moment. Building on Michael Stutz's excellent article, "Learn 10 good UNIX usage habits," this article suggests 10 more UNIX command-line commands, tools, and techniques that may make you more productive as a UNIX command-line wizard.

mod_perl Data-Sharing Techniques

2008-05-24T21:42:00.000+01:00

In this chapter, we discuss the ways mod_perl makes it possible to share data between processes or even between different handlers.

FreeBSD with AMD

2008-05-22T21:12:00.000+01:00

An automounter allows the binding of a directory name to a filesystm to be delayed until the name is referenced. This can be advantageous merely to reduce the number of simultaneous mounts, but it can improve system reliability, simplify administration and provide transparent redundancy as well. Examples of automouters are autofs (supplied with Linux) and automountd (supplied with SUNOS) Amd is an advanced automounter, with great flexibility. It is the default automounter pre-installed in FreeBSD and is currently maintained for over 100 operating systems by Erez Zadok. As of the fall of 2000, it is at version 6.04.more...

Building a Postfix Mail Server

2008-05-20T18:53:00.000+01:00

The Linux world has many excellent programs for handling email: Sendmail, Exim, qmail, and Postfix are the top four mail transfer agents (MTAs). This chapter covers Postfix. Like most of the post-Sendmail generation of MTAs, Postfix is designed from the ground up to be secureable and robust. It scales nicely from the single user who wants more control over her personal mail all the way up to the largest service provider.

Critical security update for openssl

2008-05-20T18:50:00.000+01:00

A new security advisory has recently been released relating to the Debian openssl package, and whilst most security updates are not news-worthy this one is. Read on for a brief overview of the problem.more...

Guarddog Firewall Configuration

2008-05-18T21:40:00.000+01:00

While Linux is more secure against an invasion over the Internet, more is not necessarily enough. A firewall, software that allows you fine-grained control over your connection in and out of your computer, is the next step in increasing security. While Linux has had built-in firewalling software for many years, configuration of that software was a combination of a lot of research and some cryptic commands.

compare SU and SUDO

2008-05-18T21:38:00.000+01:00

One of the things that makes Linux more secure than some operating systems is a permission system and separate logins. This adds the complication that some administrative tasks must be done using the administrator login (called root) but that is a small price to pay for the added level of security, read more...

How a Unix machine boots

2008-05-18T21:35:00.000+01:00

Ever wonder what makes a computer tick or how a UNIX® server does what it does? For those who wonder what happens when you push the power button on your computer, here's your inside look. This article discusses the different boot types, managing the IBM® AIX® bootlist, and the AIX boot sequence. After reading this article, you should have a better understanding of what exactly is happening when your server starts.

yacc and lex

2008-05-16T19:27:00.000+01:00

yacc and lex are tools for generating language parsers. We observed in Chapter 8 that your first minilanguage is all too likely to be an accident rather than a design. That accident is likely to have a hand-coded parser that costs you far too much maintenance and debugging time—especially if you have not realized it is a parser, and have thus failed to properly separate it from the remainder of your application code. more...

Sun Solaris for AMD64

2008-05-14T20:18:00.000+01:00

Sun's Solaris will soon appear in a native 64-bit version for the AMD64 architecture. While you can already run the 32-bit version of Solaris x86 today, Alan Zeichick explains the significance of this new operating system release, and highlights Sun's plans to support the AMD Opteron and Athlon 64 processors.

Analyzing Malicious SSH Login Attempts

2008-05-12T20:44:00.000+01:00

Malicious SSH login attempts have been appearing in some administrators' logs for several years. This article revisits the use of honeypots to analyze malicious SSH login attempts and see what can be learned about this activity. The article then offers recommendations on how to secure one's system against these attacks.

Linux Recovery and Boot Disk Creation

2008-05-11T19:13:00.001+01:00

This tutorial covers the creation and useage of boot floppies for system recovery.
Three recovery methods are discussed:
1- Creation / useage of a floppy with GRUB boot loader. Grub configured on floppy to point to Linux kernel on hard drive.
2- Creation / useage of a floppy with LILO on the Master Boot Record (MBR) to point to the Linux kernel on an existing hard drive for boot. This is typically done when the MBR is corrupted, overwritten by the installation of another operating system or as an alternative to configuring the hard drive MBR for dual boot, more...