KrazyWorks

Shell Scripting for HPC Clusters, Part 1

October 10, 2009 – 12:59 am

This is the first installment of a multipart guide for beginner Unix sysadmins supporting HPC clusters.
“For” and “While” Loop Constructs
The main challenge of supporting a Linux cluster is ensuring a homogeneous environment. Aside from small …

Web Hosting Providers and php.ini

October 9, 2009 – 4:07 pm

The php.ini is the primary configuration file for the PHP – a popular scripting language used for Web development. Most Web hosting providers offer preinstalled PHP on their servers. If your search on PHP has …

iPhone Photography: Making Photos Better

September 17, 2009 – 9:05 pm

The is the first installment of the three-part review of the better photo apps for iPhone. In the follow-up reviews we will look at artistic photo filters and panorama applications. If you don’t want to …

More Bad iPhone Apps

August 13, 2009 – 1:19 am

This is the second part of my review of iPhone apps unworthy of your ninety nine cents. You can read the first part here.
Certain applications are well-written and might have been quite useful, if …

Automatically Validate HTTP Proxies

August 5, 2009 – 4:14 pm

Let’s say you downloaded a long list of Web proxy servers. Now you are stuck with the task of weeding out the proxies that are dead, slow, fake, or otherwise unusable. There are some applications …

Shell Random Number Generator

August 4, 2009 – 2:58 pm

Sometimes, in the course of writing shell script, a need arises for some random input. Using the built-in $RANDOM shell variable will give you a random number from 0 to 32767 . Let’s take a …

Bad iPhone Apps

July 29, 2009 – 4:37 pm

Oh quit your whining, you will say, they are just a couple bucks each, so no big loss if some iPhone apps turn out to be trash. True, but they are so addictive. My first …

Protected: WordPress Usage Example

July 16, 2009 – 3:56 pm

There is no excerpt because this is a protected post.

iPhone: No Clicking Sound

July 16, 2009 – 4:58 am

Many long-time iPhone users are familiar with the mystery of disappearing keyboard clicking sounds (among other sound effects). Here are a few things you can try before you take your fruity phone back to the …

The Follies of Traffic Driving

July 11, 2009 – 4:31 pm

Imagine a busy street in the city with sidewalks packed with pedestrians. Hundreds of people are pushing and shoving, eating, arguing, talking on their cell phones and not paying any attention to each other. Suddenly, …

Testing Filesystem Performance with Bonnie++

July 10, 2009 – 4:33 pm

Bonnie++ is a benchmark utility designed to test performance of hard drives and filesystems by simulating various types of disk I/O. Bonnie++ may be used to test local disks as well as network-mounted filesystems. It …

Tracking Prices of Hard Drives

July 5, 2009 – 5:40 pm

It seems that only a year ago terabyte hard drives were a novelty item. Today they are on clearance at computer stores trying to free up the shelves for 1.5Tb drives and the 2Tb hard …

Wget and User-Agent Header

June 29, 2009 – 12:41 pm

As you may already know, Wget is a popular (particularly in the Unix world) command-line downloader and Web crawler application. You can read more about Wget in one of my earlier posts on the subject. …

Numeric File Permissions in Unix

June 27, 2009 – 7:50 pm

Suppose you are working with a Web server and your task is to make sure that no files or directories have permissions “777”. It would be easy to just recursively change permissions for all files …

Duplicating WordPress Installation

June 25, 2009 – 2:51 pm

Whenever you upgrade your WordPress installation or do development work, it is always a good idea to be working on a copy of your main site and not on the real thing. Copying WordPress installation …

Restart Apache, MySQL When Low on Memory

June 25, 2009 – 4:27 am

Heavy traffic, hungry SQL queries, leaky applications will eventually leave your server low on memory. Apache will go on a hunt for swap space and MySQL will start freezing in thoughtful contemplation. Your hard drives …

MySQL Global Search and Replace Script

June 25, 2009 – 3:53 am

A day will eventually come when your need to find and replace a string of text in your database. You don’t know which row, or which column, or which table. Heck, you may not even …

Passing MySQL Commands from Shell Script

June 25, 2009 – 3:30 am

Running MySQL commands from a shell script is a relatively simple task that has a lot of people baffled. Some say its too complicated and suggest using PHP or Perl, others claim doing so is …

WordPress Directory Listing Risk

June 11, 2009 – 11:36 pm

A large number of WordPress directories do not have an index file. This is particularly dangerous in case of the plugins directory. If your server allows directory listings, a potential attacker may see which plugins …

DownThemAll! “No free space” error

May 18, 2009 – 6:12 pm

DownThemAll! is a popular download manager for Firefox Web browser supporting multi-part downloading with ability to pause and restart downloads without losing data. A common problem encountered while using DownThemAll! is the dreaded “no free …

Controlling Process CPU Utilization

March 9, 2009 – 12:36 pm

Let’s say there is a process on your Unix/Linux system that sometimes tends to consume all CPU resources and become unresponsive. At the same time, you do not want to terminate the process at the …

Encoding Videos for XBox 360 and PS3

January 1, 2009 – 4:47 pm

Both Xbox 360 and PS3 support a variety of video codecs and are capable of playing high-definition video files. One of the most popular formats for HD video files is Matroska (MKV), which provides excellent …

Commands & Shells »

Plundering Facebook Photo Albums

Let’s imagine you need to download all the photos in a Facebook photo album. It can be a public album, a friend’s, or even your own. Sure, you can do this manually, but you probably …

Scraping a Web Page in Bash

Just a scripting exercise because I need to do something important, but I am procrastinating. The idea is simple: grab some URL with text containing somewhat structured data and convert it into a spreadsheet. I …

Processing Videos with ffmpeg and Lightroom

On occasion I wondered how to apply advanced photo filters to my lackluster GoPro and drone videos. You know, not the basic exposure/contrast/saturation or the cheesy special effects you find in video editors, but something …

Searching Twitter

Here are just a few hopefully useful tips for searching Twitter to get more relevant results and buy cheap twitter followers.

Scraping a Web Page in Bash

Generating Random Text Files for Testing

Sometimes you need dummy folder structures populated with random data for testing your various scripts and processes – backups, file transfers, encryption, compression, etc. Every time I need something like this, I end up writing …

Finding Cron Jobs

Cron is an indispensable tool for system administration. The difficulties in working with cron in a large environment stem from its decentralized nature. Cron jobs multiply like rabbits, and keeping track of them is not …

Understanding Memory Utilization in Linux

This is a depressing – and all-too-common – scenario: a user runs the free command and opens a support case because he sees zero “free” memory on the server.

Validating HTTPS Cache Peers for Squid

I have a squid proxy server that uses a long list of authenticated cache peers in a round-robin configuration. The process looks something like this:

Verifying SNMP Connectivity on Multiple Hosts

I needed to check if SNMP was accessible on whatever live servers that existed in a particular subnet. Here’s a quick script to do this.

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