Posted in Distributed Systems, Programming on March 16th, 2009 by Philipp C. Heckel – 2 Comments
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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Posted in Distributed Systems, Virtualization on November 1st, 2008 by Philipp C. Heckel – Be the first to comment
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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Posted in Linux, Synchronization on October 25th, 2008 by Philipp C. Heckel – 2 Comments
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:
Warning: inconsistent state.
The archive file is missing on some hosts.
For safety, the remaining copies should be deleted.
Archive are96968da50882488164ef52510703a8e on
host <UserAs-local-hostname> is MISSING
Archive ar664775fc717afcf6cc46edbc47d25641 on ... read more »
Posted in Linux, Office, Synchronization on September 30th, 2008 by Philipp C. Heckel – 47 Comments
GCALDaemon is a great tool to synchronise 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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Posted in Linux, Multimedia on July 29th, 2008 by Philipp C. Heckel – 4 Comments
Since nearly everybody in the US and more and more Europeans have an iPod and the whole world loves Youtube, wouldn’t it be nice to copy these flash streaming videos (flv-files) to your iPod Video? — Yes, it is possible. And I will tell you how.
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Posted in Office on July 29th, 2008 by Philipp C. Heckel – Be the first to comment
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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Posted in Office on May 16th, 2008 by Philipp C. Heckel – 4 Comments
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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Posted in Linux, Synchronization on May 16th, 2008 by Philipp C. Heckel – 8 Comments
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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Posted in Programming on May 16th, 2008 by Philipp C. Heckel – 76 Comments
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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Posted in Linux on May 15th, 2008 by Philipp C. Heckel – 1 Comment
Most of the Ubuntu users know the situation: You’re sitting in a public place, let’s say a lecture or a café, 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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