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Unix+clones

OpenOffice 2.0: Creating database forms

Post date: December 13, 2005, 12:12 Category: Software Views: 3389 Comments
Tutorial quote: ather than having a shallow affair with OpenOffice 2.0, we can use it to get a little more intimate with the data. We can even badger it into forming relations. Why force your database tables into a marriage with OpenOffice? Because, as with human relations, life -- and data -- are pretty meaningless without tight connections.

This tip on creating forms is part of a series I'm writing on OpenOffice.org 2.0 Base. So far, I've discussed making a plain database from scratch, creating tables, entering data using the table editor and a simple form and creating a view of a table or tables.

Let's start off with a description of what table relations are anyway, then discuss how to create a data entry form like this one, which has data from two related tables.
Linux

Hardening Linux: a 10 step approach to a secure server

Post date: June 22, 2005, 10:06 Category: Security Views: 4062 Comments
Tutorial quote: The Internet has become a far more dangerous place than it was 20 years ago. Nowadays, Operating System and application security is an integral part of a server configuration and, while firewalls are very important, they are not the panacea.

This list of steps is intended as a guideline with a practical approach. We’ll try to provide a complete picture without getting into unnecesary details. This list won’t replace a good book on secure systems administration, but it will be useful as a quick guide.

Before we get started it’s worth to mention that security is not a status: it’s just a process. The correct initial setup of the server only provides a good start and helps you get half the way through. But you actually need to walk the other half of the road, by providing proper security vigilance, monitoring and updating.
Linux

Xen Virtualization and Linux Clustering, Part 1

Post date: January 21, 2006, 06:01 Category: System Views: 4187 Comments
Tutorial quote: Have you heard about Xen virtualization and want to get some hands-on experience? Do you want to experiment with Linux clustering but only have a single computer to devote to the cause? If you answered yes to either of these questions, keep reading.

In this article, I briefly introduce the concepts of Xen virtualization and Linux clustering. From there, I show you how to set up multiple operating systems on a single computer using Xen and how to configure them for use with clustering. I should point out that a cluster implemented in this manner does not provide the computational power of multiple physical computers. It does, however, offer a way to prototype a cluster as well as provide a cost-effective development environment for cluster-based software. Even if you're not interested in clustering, this article gives you hands-on experience using Xen virtualization.
Unix+clones

Execute Commands on Multiple Linux or UNIX Servers part II

Post date: December 28, 2005, 10:12 Category: System Views: 3851 Comments
Tutorial quote: I have already covered how to execute commands on multiple Linux or UNIX servers via shell script. The disadvantage of script is commands do not run in parallel on all servers. However, several tools exist to automate this procedure in parallel. With the help of tool called tentakel, you run distributed command execution. It is a program for executing the same command on many hosts in parallel using ssh (it supports other methods too). Main advantage is you can create several sets of servers according requirements. For example webserver group, mail server group, home servers group etc. The command is executed in parallel on all servers in this group (time saving). By default, every result is printed to stdout (screen). The output format can be defined for each group.
Linux

Arcane Linux Commands: dc

Post date: December 31, 2007, 01:12 Category: Miscellaneous Views: 4027 Comments
Tutorial quote: If anybody within earshot of you is struggling to learn sed and ever remarks "This is like learning Klingon! Could they make it any more cryptic?", you can always point them to dc.

dc is the command-line Unix "Reverse-Polish Notation"(RPN) calculator. The name stands for "desktop calculator". OK, so what is a Polish calculator and why would you want to reverse one? The math that you do in school uses infix notation, with the operator between the numbers (3 + 5). Prefix notation puts the operator first (+ 3 5) and is what the Lisp language uses. The prefix notation is known as "Polish notation" after the nationality of Jan Łukasiewicz who invented it. Postfix notation, then, has the operator at the rear (3 5 +), and so is also the reverse of Polish notation.

What's the difference? In computer programming, you have to specify what order you want a multi-part calculation to be in. Everybody is familiar with the old problem of A*B-C. For A=5, B=3, C=2, multiplying first and subtracting second gives you 13, while subtracting first and multiplying second gives you 5. To specify which operations you want performed first, you have to either memorize the complex orders of operations (which change from one language to the next) or use a lot of parenthesis ((A*B)-C) or (A*(B-C)). Hey, that's what everybody complains about in all those languages that use parenthesis!
RedHat

My First Linux Server, Part 1

Post date: April 14, 2005, 22:04 Category: Miscellaneous Views: 5016 Comments
Tutorial quote: Many small businesses are turning to Linux as way to swim against the tide of rising software costs. Are you thinking about diving into Linux for your small business? From the outside, Linux can appear to be a deep ocean of strange jargon in unchartered waters. Who has the time to wade through all that to save a few clams? With Linux, it's not a sink or swim proposition.

Linux is now a lot simpler than you may think. We can provide you with the easiest, simplest, no-problem process for installing Linux on a PC. After going through this simple installation process, you will have a basic machine that you can configure into any kind of server, workstation, or office desktop. Future articles in this My First Linux Server series will help you build productive, Linux-based servers and small office workstations.

The best choices for your first Linux machine are probably the popular Red Hat Linux or SUSE Linux, primarily because both are easy to install and configure. Additionally, these companies are sound choices for the home office or small business. Both vendors have specialized in Linux for many years and offer full corporate product lines supporting your expansion.
Linux

Creating Really Teensy ELF Executables for Linux

Post date: April 12, 2005, 18:04 Category: Miscellaneous Views: 3168 Comments
Tutorial quote: If you're a programmer who's become fed up with software bloat, then may you find herein the perfect antidote.

This document explores methods for squeezing excess bytes out of simple programs. (Of course, the more practical purpose of this document is to describe a few of the inner workings of the ELF file format and the Linux operating system. But hopefully you can also learn something about how to make really teensy ELF executables in the process.)

Please note that the information and examples given here are, for the most part, specific to ELF executables on a Linux platform running under an Intel-386 architecture. I imagine that a good bit of the information is applicable to other ELF-based Unices, but my experiences with such are too limited for me to say with certainty.

The assembly code that appears in this document is written for use with Nasm. (Besides being more appropriate for our needs, Nasm's syntax beats the hell out of AT&T syntax for anyone who learned x86 assembly language before learning to use Gas.) Nasm is freely available and extremely portable; see http://nasm.sourceforge.net/.

Please also note that if you aren't a little bit familiar with assembly code, you may find parts of this document sort of hard to follow.
Linux

Rip DVDs in Linux the (Semi-)Easy Way

Post date: December 8, 2007, 14:12 Category: Multimedia Views: 3958 Comments
Tutorial quote: With its hacker-friendly aesthetic and open source mentality, you'd think a Linux desktop would be the best place to assert your digital rights—you know, make backup copies of your DVDs, convert them for iPods, that kind of thing.

And you'd be half right. There are plenty of programs that let you take control of your video discs, but they're only useful if you can make it through a maze of configuration menus, command line options, choices about bit rates and codecs, and the occasional confusing message about a missing library.

I've tried out a good number of DVD ripping and conversion programs, and I've made peace with one method, and one program, that gets the job done more often than not. It's not exactly one-click, but once your system is set up, you can drop in DVDs and back them up or convert them with relative ease.

Note on system differences: I set up my ripping/burning system on a Lenovo Thinkpad T61 running a brand-new installation of Ubuntu 7.10 (Gutsy Gibbon). As with so many things Linux, packages and commands may vary based on your system. But for the most part, the tools I use in this walkthrough work across distributions and on both major desktop environments, GNOME and KDE.
Linux

Three tools to help you configure iptables

Post date: May 25, 2005, 14:05 Category: Network Views: 3530 Comments
Tutorial quote: Every user whose client connects to the Internet should configure his firewall immediately after installation. Some Linux distributions include firewall configuration as a part of installation, often offering a set of defaults configurations to choose from. However, to ensure that your machine presents the minimum "attack surface" (a measure of the number of vulnerable ports, user accounts, and sockets exposed to attack) to the predatory inhabitants of the Internet, you may need to do some manual configuration of your firewall. Here are three tools that can help.
The Linux kernel (version 2.4 onwards) contains a framework for packet filtering and firewalling using netfilter and iptables. Netfilter is a set of hooks inside the Linux kernel that allows kernel modules to register callback functions with the network stack. Iptables is a generic table structure for the definition of rulesets. Each rule within an IP table consists of a number of classifiers (iptables matches) and one connected action (iptables target). Iptables has extensive documentation that can be accessed online or by typing man iptables at the command line. Yet despite the depth of the documentation available for iptables, its complexity can be baffling.
Linux

Linux Web Filtering in 7 steps

Post date: April 12, 2005, 18:04 Category: Network Views: 4539 Comments
Tutorial quote: How to install a transparent Squid proxy server with real-time HTTP virus scanning on Mandrake 10.0 using DansGuardian and ClamAV?

People quickly and easily access volumes of research on the Internet and correspond with a mouse click. For more and more companies, content filtering is part of the large battle to combat all kinds of online threats, including hackers, worms and viruses. Linux content filtering allows administrators to configure and manage Internet access across the entire network and to block unwanted Web content like pornography, shopping Web sites, games and gambling.

This guide contains all the necessary information for installing and understanding the architectural layout of the implementation. It was written with the assumption that you understand how to install programs and have a basic understanding of Linux Mandrake. This includes installing Linux Mandrake and RPM packages, editing files, making directories, compiling software and understanding general UNIX commands. This guide doesn’t explain how to use or configure Squid, DansGuardian and ClamAV but information on where to obtain this information can be found in the “Additional information” section.
Web-based applications and online marketing solutions - LumoLink