My name is Philipp C. Heckel and I write about nerdy things.

Blog


  • Mar 16 / 2009
  • 3
Distributed Systems, Programming

KadS: a secure version of the Kademlia protocol

There are various peer-to-peer protocols out there. All of them focus the decentralisation of storage and other system resources. Most implement a distributed hash table (DHT) to store information. That is, each node of the network only holds a small part of the hash table but is able to locate and retrieve any requested entry. Kademlia, a protocol designed by two NYU students in 2002, is one of them.

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  • Nov 01 / 2008
Distributed Systems, Virtualization

Server Virtualization with VMware Infrastructure (vSphere)

In the last few years, the Internet has become increasingly important in various fields of our lives. Not only personal households have discovered the nearly endless possibilities of the Web, but also companies found many different ways of gaining revenue through the online world. Most of the global players and many medium-sized IT companies have realized what opportunities the Web and its technologies provide and used them to build up new services for consumers and businesses. In order to compete with the evolving market, companies of traditional business areas such as newspapers or TV broadcasting companies had to diversify their product lines and are forced to react in a fast, flexible and cost efficient way on every day’s changes of demands and technologies. In fact, every company has to adapt these technologies efficiently to have a chance in the growing market.

As it brings its benefits, cost savings and new customers, every new technology also comes with the more or less known downsides. Even if IT managers are qualified to consider most of the details in how to use and implement them, new software, hardware or resources will – no matter what – always cause unpredicted problems. Due to the IT dependence of today’s companies, every downtime, bug or system overload of a production system directly results in declining profits and higher costs. Especially for service providers, every downtime is business critical to many dependent companies and has to be prevented.

Therefore, companies spend a considerably high amount of money and time to create a stable, flexible and extensible IT environment that supports their business by minimizing risks, increasing availability and allowing to provide better service levels to customers.

Virtualization is a key technology that addresses to achieve these goals. It allows to run multiple virtual computers on the same physical system. By creating an abstraction of the underlying hardware, it allows to execute a variety of virtual machines (VMs) on top of a virtualized hardware.

This article will discuss how the technology of virtualization works, what advantages it offers and why it is an essential part of today’s data centers. The focus will be the server virtualization solution VMware Infrastructure, the flagship product suite of VMware Inc.

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  • Oct 25 / 2008
  • 3
Linux, Synchronization

Unison & multiple hosts: “Warning: inconsistent state.”

As some of you might know, Unison is this great tool that allows bidirectional synchronisation of two hosts, – no matter which operating system they’re running… Well, at least the well known ones are supported.

Since Unison can also be used to sychronise more than two hosts, it’s perfect for big amounts of data that has to be shared in a team.

A scenario like this is possible and works for me: UserA <-> Server <-> UserB.
But of course, also other users could sync with the server. Unison rocks!

Today, after reinstalling his OS, my friend got the following error message:

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  • Sep 30 / 2008
  • 48
Linux, Office, Scripting, Synchronization

GCALDaemon deb-package for Ubuntu/Kubuntu

GCALDaemon (project doesn’t exist anymore, was at http://gcaldaemon.sourceforge.net/) is a great tool to synchronize many of Google’s services such as Google Calendar and Contacts with your local PC. Unfortunately, the installation on Ubuntu/Kubuntu and any other Linux distribution is still not the most comfortable. For this reason, I sat down some hours and packed the tool into a deb-package and additionally added a nice command line tool to simplify some of the basics.

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  • Jul 29 / 2008
  • 4
Office

Excel: Add weekdays to date (VBA)

Since many companies work with Microsoft Excel it is often necessary to be inventive in order to implement the required functionality in your worksheet.

In some applications you might want to calculate a deadline date within the week, e.g. to make sure that a product or service will be delivered within a time frame of max. 10 working days.

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  • May 16 / 2008
  • 4
Office

Launch Nautilus in the current working directory

Working on the console is sometimes tiring, especially when you have to rename files. Using Nautilus is much quicker for these types of actions. The problem is, that if you’re working in a deep depth of your file tree and your path is very long, it may take you some extra seconds to open this path in the Nautilus browser. So wouldn’t it be much easier to simply type naut on the console to open Nautilus with the current working directory?

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  • May 16 / 2008
  • 8
Linux, Synchronization

Unison 2.27.57 on Debian Etch and Ubuntu Hardy

The good thing about the file sync tool Unison is, that it’s available for several operating systems. This is great for groups working on different systems (Mac, Linux and Windows) but want to share and synchronize files on a remote server.

Well, the bad thing about Unison on the other hand is, that its backwards compatibility is anything but great, so that you have to make sure that everybody in the team uses the same version. And this can be tricky depending on what system you are using.

My home system is Ubuntu Hardy, the remote server system is Debian Etch. Both come with Unison 2.16.13 which would be great if not Apple’s new Leopard brings the newest version 2.27.57. Long story short, I needed the newest version on Hardy and Etch.

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  • May 16 / 2008
  • 209
Programming

Roundcube login via PHP script

Roundcube is an AJAX/PHP based e-mail application which is really flexible and easy to use in comparison to other free web based solutions.

For the customer interface of Silversun, I wanted to use RC as the internal web mail application and therefore had to embed it into my system. To avoid that the customer has to log in twice (customer interface and Roundcube), I had to simulate the login request with a PHP script.

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  • May 15 / 2008
  • 1
Linux

Switch off sound on Ubuntu before login

Most of the Ubuntu users know the situation: You’re sitting in a public place, let’s say a lecture or a cafĂ©, and you forgot to switch off the sound of your laptop. Unfortunately, you can’t avoid the first short drumming. But by using the following command, it is at least possible to switch off the longer welcome melody of Ubuntu before you actually log in.

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