Category Archives: Personal

Installing Debian on a Sheevaplug into Flash

Ok, so you are looking for a comprehensive guide on how to install a modern Debian system into the Flash memory of your Sheeva Plug? Your googling has paid of – look no further!

What we will do in this guide:

  • Update the bootloader to a recent version which supports direct booting from ubifs partions. So you can just use the stock Debian kernel without any hassle or SD card.
  • Install Debian to a ubifs filesystem on the Sheevaplug flash.

Continue reading Installing Debian on a Sheevaplug into Flash

Fixing Authentication of ownCloud for webfaction

So these days I was playing with setting up ownCloud – a cool application to server your own content. I was especially looking into having an online calender which is not saved at Google.

Now, the installation is straight forward. But once you start pointing your Calender program or browser to http://DOMAIN.TLD/apps/calendar/caldav.php/principals/USERNAME the password dialog always popped up, no matter if the password was correct or not.

After some investigations it turned out that this is caused by the special setup of my webspace provider. Basically, ownCloud extracts the username and password from the HTTP header via mod_rewrite and provides it to PHP over environment variables. Unfortunately, this mechanism is disabled by webfaction.

Fortunately they also propose a solution: Instead of passing the header over environment variables I have to pass it over the URL via an internal redirect. To achieve this, I’ve inserted a new conditional rule into my .htaccess file:

RewriteCond %{HTTP:Authorization} ^Basic.*
RewriteRule ^(.*) $1?Authorization=%{HTTP:Authorization} [QSA,C]
RequestHeader unset Authorization

This rule is active once a authentication header is transmitted. In that case the Authorization header is inserted in the query string. Additionally the Authorization header is removed since we end up doing endless recursions otherwise.

The only thing left now is to also tell ownCloud how to parse this new part of the query string. For that just add the following code to  ./lib/base.php around line 350 inside the init() function:

//sett http auth headers for Webfaction workaround
if(isset($_GET['Authorization']) && preg_match('/Basic\s+(.*)$/i', $_GET['Authorization'], $matches))
	list($name, $password) = explode(':', base64_decode($matches[1]));
	$_SERVER['PHP_AUTH_USER'] = strip_tags($name);
	$_SERVER['PHP_AUTH_PW'] = strip_tags($password);

Congratulations! You have ownCloud up and running on webfaction.

HOWTO: Fixing a broken EDID EEPROM with a Bus Pirate v4

This post is about fixing a broken EDID ROM in a monitor. There are several ways to do this. Typically this involves writing the EEPROM with the Windows only tool PowerStrip (see here for a HOWTO) . Here I want to present an alternative solution using the Dangerous Prototypes Bus Pirate – a device which every hardware hacker with self-respect should have anyway. You should already be tech-savvy to attempt this procedure.


So I own 3 Samsung Syncmaster 2343BW with a staggering 2048×1152 pixels of resolution on 23″. When I bought them 3 years ago – this was really amazing. (Nowadays, such monitors are not even for sale anymore… but there is the ipad… Hopefully Apple sets a trend here for higher resolution…

So one of these monitors often suffers from a broken EDID EEPROM. Since this ROM is used to store all important information for Plug&Pray, the monitor not being detected anymore at all. I had this happen to me 3 times during warranty and they always exchanged the whole motherboard.  But unfortunately continues to appear after warranty, so I set out to fix it myself.

Continue reading HOWTO: Fixing a broken EDID EEPROM with a Bus Pirate v4

Finally finished my bachelor thesis!

Hallo all,

quite some time went by since I last blogged. I was just so immersed with work (and an amazing holiday in Australia!) and I just had no time for blogging. But now it’s time that I can announce one finished mile stone:

I’v finished my Bachelor Thesis

It tourned I’m fast in writing software but awfully slow with normal text.. But I’m quite proud of the result anyway. 🙂

Download: Bachelor Thesis