Oracle Virtualization and Cloud Consulting
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Free on-line Introduction to Linux course

In August 2014, more than 300,000 people registered for the first offering of the Introduction to Linux course. This popular Massive Open Online Course (MOCC) is taught by the Linux Foundation, and hosted on edx. The same course starts again on January 5, 2015. The course is designed for people who have limited or no previous exposure to Linux.

How to split an image for visual effects

Suppose that you've just taken a panorama photograph with your fancy digital camera. You can display the picture as is on your blog. Or you can be a little bit more creative. How about splitting it up into 3 rectangular pieces?

Tools for checking broken web links - part 2

Part 1 of this 2-part series on Linux link checking tools reviewed the tool linkchecker. This post concludes the series by presenting another tool, klinkstatus. Unlike linkchecker which has a command-line interface, klinkstatus is only available as a GUI tool.

Tools for checking broken web links - part 1

With a growing web site, it becomes almost impossible to manually uncover all broken links. For WordPress blogs, you can install link checking plugins to automate the process. But, these plugins are resource intensive, and some web hosting companies (e.g., WPEngine) ban them outright. Alternatively, you may use web-based link checkers, such as Google Webmaster Tools and W3C.

How to redirect sudo output to a file requiring root permission

sudo is the recommended way to execute a command which requires root permission. In effect, the target command takes on the permission of root without having to provide the root password. Consider the following scenario. In order to save the changes made to the iptables firewall rules, I need to run the following command which outputs the changes to a file with root permission. $ sudo iptables-save > /etc/iptables/rules.v4bash: /etc/iptables/rules.v4: Permission denied

Upgrade from Fedora 19 to 20 using fedup

The recommended upgrade method for Fedora is to use the fedup tool. Below is my experience in following the fedup procedure to upgrade from Fedora 19 to 20. The upgrade was done over the Internet ("network upgrade") instead of from a local DVD media.

  1. Back up all important data in the system.

How to optimize PNG images

table, th, td { border: 1px solid white; border-collapse: collapse; } th,td { padding: 15px; } My previous post introduces some tools to optimize JPEG images. The focus of this post is on optimizing PNG images. Two complimentary tools will be presented: optipng, and pngquant.

How to optimize JPEG images

table, th, td { border: 1px solid white; border-collapse: collapse; } th,td { padding: 15px; } Poor load time degrades the user's experience of a web page. For a web page containing large images, optimizing images can significantly improve the load time performance which leads to better user experience. Moreover, if a web site is hosted on a cloud service which charges for cloud storage, compressing images can be financially worthwhile.

Create video screencasts using recordmydesktop

Why make a video screen capture, aka screencast? Some possible reasons are:

  • Create a software demo.
  • Capture a video game session for playback later.
  • Keep a record of what transpires on the computer screen.

I create screencasts mainly for recordkeeping. As a result, I don't expect to edit the output video, for example, to obfuscate sensitive data, or to insert call-outs to draw attention to specific screen areas.

Building a firewall for a Debian web server

This post addresses how to configure the Linux firewall to protect a Debian-based web application server. While there are GUI tools for the job, we will focus on the command-line tool iptables. The scenario is that you have just installed Debian (or Ubuntu) on a server connected to the Internet. This will be used as a web server hosting your WordPress blog. I assume that you already have Apache, and WordPress installed.

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