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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:9708 | -nixcraft, June 24, 2012

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:9691 | -nixcraft, December 4, 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:9611 | -nixcraft, December 14, 2011

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:9504 | -nixcraft, March 13, 2008

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:9488 | -nixcraft, November 21, 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:9457 | -nixcraft, March 8, 2013

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:9406 | -nixcraft, October 11, 2008

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:9403 | -nixcraft, September 3, 2009

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:9395 | -nixcraft, October 22, 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:9375 | -nixcraft, March 7, 2013

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. Ive 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:9349 | -nixcraft, December 19, 2007

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:9299 | -nixcraft, August 24, 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:9153 | -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:9141 | -nixcraft, December 8, 2012

Tutorial: FreeBSD Static Routing

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For one machine to be able to find another over a network, there must be a mechanism in place to describe how to get from one to the other. This is called routing. This how to describes FreeBSD default routing and static routing configuration for particular subnet / host. read more...
permapage | score:9093 | -nixcraft, February 4, 2008

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:9074 | -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:9026 | -nixcraft, December 16, 2009

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:8994 | -nixcraft, November 23, 2012

Best Nmap Command Examples For Network Auditing

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Nmap is short for Network Mapper. It is an open source security tool for network exploration, security scanning and auditing. However, nmap command comes with lots of options that can make the utility more robust and difficult to follow for new users.

The purpose of this post is to introduce a user to the nmap command line tool to scan a host and/or network, so to find out the possible vulnerable points in the hosts. You will also learn how to use Nmap for offensive and defensive purposes. read more...
mail this link | permapage | score:8941 | -nixcraft, November 29, 2012

Unix: Show Network Interface Card Statistics

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The nicstat command is top like utility for network interface card (NIC). It displays information and statistics about all your network card such as packets, kilobytes per second, average packet sizes and more. It works under Solaris and Linux operating systems.

In this post, I will explain how to install and use the nicstat command to find out stats about your NICs under Debian / Ubuntu / RHEL / CentOS Linux operating systems. read more...
permapage | score:8933 | -nixcraft, March 25, 2013
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