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OpenBSD Tutorial: Configure Ralink USB Wireless Adapter

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I brought a USB 2.0 wireless adapters based on the Ralink RT2700U, RT2800U and RT3000U chipsets. How do I configure and use it under OpenBSD operating systems?

This usb wireless adapter works out of box under OpenBSD and Linux operating systems. Under OpenBSD you need to use run driver. read more...
permapage | score:9719 | -nixcraft, December 4, 2012

Unix: Shell Script Wrapper Examples

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Shell script wrappers can make the *nix command more transparent to the user. The most common shell scripts are simple wrappers around third party or system binaries. A wrapper is nothing but a shell script that includes a system command or utility.

Linux and Unix like operating system can run both 32bit and 64bit specific versions of applications. You can write a wrapper script that can select and execute correct version on a 32bit or 64bit hardware platform. In cluster environment and High-Performance computing environment you may find 100s of wrapper scripts written in Perl, Shell, and Python to get cluster usage, setting up shared storage, submitting and managing jobs, backups, troubleshooting, invokes commands with specified arguments, sending stdout to stdout and stderr to stderr and much more.

In this post, I will explains how to create a shell wrapper to enhance the basic troubleshooting tool such as ping and host. read more...
mail this link | permapage | score:9652 | -nixcraft, June 24, 2012

Linux Iptables Examples

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Linux comes with a host based firewall called Netfilter. It is a set of hooks inside the Linux kernel that allows kernel modules to register callback functions with the network stack. A registered callback function is then called back for every packet that traverses the respective hook within the network stack.

This Linux based firewall is controlled by the program called iptables to handles filtering for IPv4, and ip6tables handles filtering for IPv6. This tutorial list most common iptables solutions required by a new Linux user to secure his or her Linux operating system from intruders. read more...
mail this link | permapage | score:9573 | -nixcraft, December 14, 2011

HowTo: HTTP Status: 206 Partial Content and Range Requests Using Curl

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The HTTP 2xx class of status codes indicates the action requested by the client was received, and processed successfully. HTTP/1.1 200 OK is the standard response for successful HTTP requests. When you type www.cyberciti.biz in the browser you will get this status code. The HTTP/1.1 206 status code allows the client to grab only part of the resource by sending a range header. This is useful for:

* Understanding http headers and protocol.
* Troubleshooting network problems.
* Troubleshooting large download problems.
* Troubleshooting CDN and origin HTTP server problems.
* Test resuming interrupted downloads using tools like lftp or wget or telnet.
* Test and split a large file size into multiple simultaneous streams i.e. download a large file in parts. read more...
mail this link | permapage | score:9443 | -nixcraft, November 21, 2012

Linux Hard Disk Encryption Tutorial

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I carry my Linux powered laptop just about everywhere. How do I protect my private data stored on partition or removable storage media against bare-metal attacks where anyone can get their hands on my laptop or usb pen drive while traveling? read more...
permapage | score:9311 | -nixcraft, October 22, 2012

Tutorial: RHEL 5.3 to 5.4 upgrade

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Red Hat Enterprise Linux v5.4 has been released and available via RHN for immediate update. The new version includes the kernel-based virtual machine (KVM) virtualization, next generation of developer features and tools including GCC 4.4, a new malloc(). Also included clustered, high-availability filesystem to support Microsoft Windows storage needs on Red Hat Enterprise Linux.

This tutorial explains how to upgrade RHEL v5.3 to RHEL v5.4. read more...
permapage | score:9284 | -nixcraft, September 3, 2009

Boxes: Draw Text Mode ASCII-art

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Boxes command is a text filter and a little known tool that can draw any kind of ASCII art box around its input text or code for fun and profit. You can quickly create email signatures, or create regional comments in any programming language. This command was intended to be used with the vim text editor, but can be tied to any text editor which supports filters, as well as from the command line as a standalone tool. read more...
permapage | score:9258 | -nixcraft, June 12, 2012

HowTo: Connect two Wireless Routers

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You can setup a wireless connection between two routers only so that it will link a wireless network to a wired network allowing you to bridge two networks with different infrastructure. You can find wireless access points products that offer either a "bridge" mode or a "repeater" mode. In this post I'm going to explain three popular open source choices that can be used for setting up a wireless bridge. read more...
permapage | score:9253 | -nixcraft, September 4, 2012

Linux trickle: Bandwidth Throttling for Bash Shell

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I am using a bash shell under Ubuntu Linux operating system. Sometime I need to restrict my own Internet bandwidth for all my shell applications such as ftp, sftp, wget, curl and friends. How do I limit the network speed under bash without setting up a complicated firewall and tc rules. read more...
permapage | score:9240 | -nixcraft, December 8, 2012

Book Review: The Book Of Gimp

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I usually use GIMP (the "GNU Image Manipulation Program") for editing photos, changing colors, resizing photos, applying significant effects and more. It is a free software alternative to Adobe Photoshop. It is also quite popular with graphics artists and webmasters who wants to edit digital images. GIMP is not just a Linux specific program. It works on all leading operating systems, i.e., Mac OS X, MS-Windows and Unix variants. However, like many other powerful open source software, GIMP can be difficult to master. There are many options and plugins. So if, you are looking to learn or master the GIMP program, give The Book of GIMP a try. read more...
mail this link | permapage | score:9237 | -nixcraft, March 8, 2013

Debian / Ubuntu: Block unwanted sites with SquidGuard Web Filter

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How do I install and configure SquidGuard – a web filter plugin for Squid to restrict access to domains/URLs based upon access control lists? How do I block porn, gambling, and other web-sites using squid proxy server version 3.x under Debian or Ubuntu Linux server for my school? read more...
permapage | score:9194 | -nixcraft, August 24, 2012

Tutorial: Use Amazon Cloudfront To Speed Up Wordpress Based Site

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A typical WordPress blog contains a mix of static stuff such as images, javascript, style sheets and dynamic content such as posts, pages and comments posted by users. You can speed up your blog by serving static content via content delivery network such as Akamai, Edgecast and so on. The big boys of CDN business also offered the solution to accelerate dynamic content to improve the performance and reliability of the blog. However, solutions offered by big and traditional CDNs are expensive. Amazon cloudfront recently started to serving dynamic content at lowered price. In this blog post, I will explain:

1. How to serve your entire blog using cloudfront.
2. DNS settings.
3. WordPress settings.
4. Documenting limitations of cloudfront.
5. Documenting performance improvements. read more...
mail this link | permapage | score:9180 | -nixcraft, March 7, 2013

Tutorial: FreeBSD iSCSI Initiator Installation and Configuration

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The FreeBSD iscsi_initiator implements the kernel side of the Internet SCSI (iSCSI) network protocol standard, the user land companion is iscontrol and permits access to remote virtual SCSI devices via cam.

FreeBSD 7.x has full support for iSCSI. Older version such as FreeBSD 6.3 requires backport for iSCSI. Following instruction are known to work under FreeBSD 7.0 only. read more...
permapage | score:9169 | -nixcraft, March 13, 2008

Tutorial: See Colourised Filesystem Disk Space Usage

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The pydf command displays the amount of used and available space on your file systems, just like df command, but in colors. The output format is completely customizable.

This is a little known tool (python script) that displays the amount of disk space available on the mounted filesystems, using different colours for different types of filesystems. read more...
permapage | score:9165 | -nixcraft, June 23, 2012

Tutorial: Monitor and Log Network Traffic on RHEL Linux using vnStat

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vnstat command is a console-based network traffic monitor. It keeps a log of hourly, daily and monthly network traffic for the selected interface(s). However, it isn't a packet sniffer. The traffic information is analyzed from the proc filesystem. That way vnStat can be used even without root permissions.

This tutorial explains how to install vnstat software - a console-based network traffic monitor under CentOS or RHEL or Fedora Linux operating system. read more...
permapage | score:9132 | -nixcraft, November 23, 2012

PDFedit: A Linux PDF editor

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Adobe Acrobat is a commercial tool for manipulating PDF files. Earlier I was using CUPs - printing system, to export PDF files. I’ve also tried out gv for the same purpose. However, I needed complete editing of pdf documents. My search ended with PDFedit software, which is free and open source editor for manipulating PDF documents. The software available in both GUI and CLI (commandline) interface. read more...
permapage | score:9114 | -nixcraft, December 19, 2007

FreeBSD: Configure Apache PHP with mod_fastcgi Module

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mod_fastcgi is a cgi-module for Apache web server.

FastCGI is a language independent, scalable, open extension to CGI that provides high performance without the limitations of server specific APIs.

This article explains how to configure PHP5 - mod_fastcgi under FreeBSD operating system. read more...
permapage | score:9106 | -nixcraft, October 11, 2008

iozone Tutorial: Measure Linux Filesystem I/O Performance

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This article gives you a jumpstart on performing benchmark on filesystem using iozone a free Filesystem Benchmark utility.

Following are few situations where you may be interested in performing a filesystem benchmarking.

=> Deploying a new application that is very read and write intensive.
=> Purchased a new storage system and would like to measure the performance.
=> Changing the RAID level and would like to measure the performance of the new RAID.
=> Changing the storage parameters and would like to know the performance impact of this change

(here are some impact canvas prints) read more...
mail this link | permapage | score:8958 | -nixcraft, July 4, 2008 (Updated: April 24, 2012)

Find wireless network speed, signal strength on Linux

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Linux operating systems comes with various set of tools allowing you to manipulate the Wireless Extensions and monitor wireless networks. This is a list of tools used for wireless network monitoring tools that can be used from your laptop or desktop system to find out network speed, bit rate, signal quality/strength, and much more. read more...
permapage | score:8883 | -nixcraft, June 8, 2012

Tutorial: Identify Linux bottlenecks with kSar

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The sar command collect, report, or save UNIX / Linux system activity information. It will save selected counters in the operating system to the /var/log/sa/sadd file. From the collected data, you get lots of information about your server such as:

1. CPU utilization
2. Memory paging and its utilization
3. Network I/O, and transfer statistics
4. Process creation activity
5. All block devices activity
6. Interrupts/sec etc.

sar output can be used for identifying server bottlenecks. However, analyzing information provided by sar can be difficult, so use kSar, which can take sar output and plot a nice easy to understand graph over period of time. read more...
mail this link | permapage | score:8881 | -nixcraft, December 16, 2009
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