Steffen's Tech Blog

Recently I needed to combine two PDF documents that I created with the TurboScan App on my Iphone (file sizes 528.5 kByte and 421.9 kByte and was searching for free options I can use with Ubuntu Linux. I found the following options: The web service  http://www.mergepdf.net/ : Usability: Easy; excellent for merging PDF files Functionality: no other functions available File size of the merged file: 950.1 kByte The free online PDF editor PDF Hammer  http://www.nitropdf.com/free/hammer/index.htm . Usability: almost as easy as mergepdf Functionality: other functions available File size of the merged file: 949.8 kByte The Linux command line   pdftk too lkit:  http://www.accesspdf.com/pdftk/ Usability: follow examples on the webpage; easy if you are comfortable with the command line Functionality: other functions available File size of the merged file:  949.8 kByte The open source PDF editor PDFedit  http://sourceforge.net...

Yesterday I updated to the new Ubuntu 9.10 . The update was as usual very smoothly (I accepted the default values when ask something). After restarting, the following error message appeared: Starting Google Desktop manually via the application menu did work. Still, I had to reinstall Google Desktop  via Synaptic in order to avoid this error message during startup. The next message I got was: I clicked on "Run this action now", followed the instructions and the missing language components got installed. I used the following language settings: Afterwards I enabled the third party repositories again (in "Software Sources"): deb http://dl.google.com/linux/deb/ stable non-free deb http://linux.getdropbox.com/ubuntu karmic main deb-src http://linux.getdropbox.com/ubuntu karmic/ deb http://packages.medibuntu.org/ karmic free non-free deb-src http://packages.medibuntu.org/ karmic free non-free deb http://ftp.osuosl.org/pub/pculture.org/miro...

After I decided to scrap my more than 4 years old laptop, because it repeatedly failed after working some minutes after booting (when it fails, nothing worked usually any more than the mouse movement, sometimes even the screen display starts to blur; even booting from Live-CDs Ubuntu 8.10, etc. showed the same effect), I was looking for a secure way to delete all data. I settled with: shred -vfz -n 10 /dev/hda" from stackoverflow.com , I had to use a very small Linux distribution ( DSL ), that was running completely in the RAM in order to be able to start the shred command (with other Live-CD's the laptop was failing already before I was able to start the command via a shell). Update: This command was running nearly one week. At the end I tried to verify the success by removing the Live-CD and start to boot again. To my surprise, Ubuntu was still booting. I am still not sure, how to explain this. Anyway, I decided to remove the HD and destroy it mechanically. That shoul...

I just followed the network upgrade instructions for Ubuntu Desktops (Recommended) and accepted the default values for the questions I was asked by the update tool (e.g. disable the proprietary display driver and use the default open source driver instead). Everything went smoothly. Afterwards I enabled the third party repositories again: http://dl.google.com/linux/deb/ stable non-free http://linux.getdropbox.com/ubuntu jaunty main http://packages.medibuntu.org/ jaunty free non-free The dropbox demon wasn't running, I had to install it again with dropbox start -i I realized that my backup python script using rsync didn't work any more, so that I had to install it again with: ~/Documents/Programming/Python_scripts/backup_daily$ sudo python setup.py install Afterwards, I could enjoy the improvements and new features of Ubuntu 9.04

I tried Dropbox - a cool file-synchronization service for Windows, Mac, Linux and the Web - after hearing about it on the Macworld Video Podcast Episode from Jason Snell from Feb 13, 2009 and loved it since. Dropbox allows you to sync (and - if you want share) up to 2GB of your files and folders automatically (and for free!) simply by dragging and dropping them into the Dropbox folder that will be created by the application (by default under your home directory). If you need more space you can buy 50GB of storage for currently US$99/year. I'm impressed how easy and fast the web-based synchronization works and was amazed that it works cross-platform - even an Ubuntu repository is available. I use it now to synchronize a few files I often need on my Ubuntu desktop, my macbook and my wife's iMac. If it works as reliable as it has done in the first days I am using it and if there will be a more cheaper storage plan version (e.g. 25GB for US$49/year), I might use it even to back...

In the last months I have spent some time trying out different GUI toolkits for Python that are cross-platform (Linux, Mac OS X and Windows). I settled with PyQt . It combines Nokia's Qt cross-platform application framework with Python so you get all the power of Qt with the simplicity of Python. Other Desktop GUI frameworks I have tried are: the Tk GUI development library included in most Python distributions wxpython a blending of the wxWidgets C++ class library with Python PyGTK to use the GTK+ library Others (such as .NET using IronPython ) are not running equally good on Linux, Mac OS X and Windows as they favour Windows. From the frameworks above, PyQt  seemed the one with the most active development, the most easy usage and the best documentation. Like Qt, PyQt V4 (its newest version) is available under a variety of licenses including GNU GPL (V2 and V3; today Qt Software announced that Qt V4.5 will also be available under LGPL). If you want to write commercial applicat...

Did you ever want to download Web videos from sites such as YouTube or others (such as http://www.vidohe.com/sites.php )? Firefox 3.0 together with the free Firefox extension DownloadHelper makes this very easy (see the DownloadHelper homepage for more details). DownloadHelper even provides a Video Conversion feature to allow background conversion of the downloaded video to the format that you like (e.g. from FLV to a format that can be used by iTunes e.g. to load on your iPod or iPhone). This feature relies on FFMPEG available on your system (for Linux or Mac), which can lead to conversion failures as the version of FFMPEG may not have been compiled with the features required by the chosen conversion parameters. You can therefore recompile FFMPEG by yourself with the required features. Note: With Ubuntu 9.10 - the Karmic Koala - there is no need to recompile FFMEG. It just works fine. As an alternative, you can use an external application such as MPEG Streamclip ...

Two weeks ago I upgraded to Ubuntu 8.10 (Intrepid Ibex). The upgrade went nice and smoothly and I really like the new version (especially the improvments made in KDE). The only problem I realized afterwards was that the Skype audio settings wasn't working correctly by default. Some manual adjustments were necessary. After I have done these adjustments already several times (two PC's, GNOME and KDE), I thought it might make sense to write them down. Maybe these settings that worked for my PC's will be helpful somebody else. adjust the skype sound device options as shown in the following screenshot: adjust the Ubuntu audio settings (Volume control) according to the next 4 screenshots:

The newest version of my favorite Linux distribution ...

Following the instructions on KDE 4.1.1 Release News I updated to KDE 4.1.1 on my Kubuntu 8.04 Hardy Heron PC. Some of the instructions were a little confusing: enable "Recommended Updates (backports)" in "Software Sources" --> as "backports" are also used to describe "Unsupported updates" (--> which is not recommended for a productive system), it must be a mistake There is no authentication key for the repository containing the updated packages deb http://ppa.launchpad.net/kubuntu-members-kde4/ubuntu hardy main . This results in warnings when updating packages from this repository which leave some kind of uneasiness as using authentication keys seem an useful security measure. Besides this, the update worked well and I found now KDE 4.1.1 much more stable than KDE 4.0. In addition, most of the functionality that I used in the GNOME desktop is available. Furthermore  I like the new KDE look as well as some of its new applications (as alrea...

Recently, I spent some time to search for free, open-source alternatives for commercial mathematics programs such as Matlab and Mathcad. By far the most promising software I have found was Sage. Sage combines the power of many (currently 71) existing open-source packages into a common Python-based interface. It can be used to explore mathematical constructions in algebra, geometry, number theory, calculus, numerical computation, etc. The combination of proven open-source packages (including excellent Python packages such as Numpy, Matlibplot, Scipy and Sympy) and an excellent web browser based entry of formulas and plots in worksheets called notebooks. The usage of Python as the glue that holds all packages together provides several advantages. First you have the full power of python available in Sage. Second, you don't need to learn another specialized script language that you would otherwise not need. Excellent screencasts together with good tutorials and documentation pages p...

After reading the following article about the status of the GNOME project http://wingolog.org/archives/2008/06/07/gnome-in-the-age-of-decadence I decided to check out the KDE 4 desktop by installing the "kubuntu-kde4-desktop" package (via Adept or apt-get) and I have to admit: I really like the new KDE 4 desktop. A lot of improvements have been made compared with its predecessor. I especially like the new version of the image viewer Gwenview and Okular, KDE4's document viewer. Check out http://www.kde.org/announcements/4.0/applications.php for more details. Unfortunately, the KDE 4 desktop seem not to be stable enough for production use. At least I experienced some crashes that required reboot via " R aising E lephants I s S o U tterly B oring" . In addition, I missed some functionality. Therefore I can't recommend switching to KDE4 right now. But I decided to give it another try as soon as KDE4.1 is available from the Ubuntu repositories in the hope that ...

Yesterday, I needed my scanner the first time after installing Ubuntu 8.04. In Ubuntu 7.10 I could use the scanner as normal user with xsane. Now running xsane let to the following error message: Segmentation fault whereas running xsane as root with sudo xsane works. The following shows the current status of my investigation. sane-find-scanner let to the following output: # sane-find-scanner will now attempt to detect your scanner. If the # result is different from what you expected, first make sure your # scanner is powered up and properly connected to your computer. # No SCSI scanners found. If you expected something different, make sure that # you have loaded a kernel SCSI driver for your SCSI adapter. found USB scanner (vendor=0x04a9 [Canon], product=0x221c [CanoScan], chip=GL842) at libusb:006:008 # Your USB scanner was (probably) detected. It may or may not be supported by # SANE. Try scanimage -L and read the backend's manpage. # Not checking for parallel port scanners. # ...

If you are using the Mozilla Firefox Web browser, you can also use ScribeFire to post your blog easily from within the browser. It allows you to drag and drop formatted text from pages you are browsing, take notes, and post to your blog. You can even add easily labels to your post. Everything works very fast. As Firefox is a cross-pattform browser, you can use it on Linux/Mac/Windows. You can read more about ScribeFire on http://www.scribefire.com/ where you can also find the link to install it from the Mozilla Add-ons site. Somehow the length of the posts seem to be limited as I have noticed that longer posts (such as my post from March 4, 2008) will be not loaded completely in the ScribFire Editor, but I haven't found any information about the maximum allowed length of a post.

As I did use different computers at home (mainly Ubuntu and Mac OS) to write the post, I did appreciate that the document was always online although I had sometimes (especially at the end, when the document was already quite big) problems with lost connections that caused loss of some changes. I didn't experienced this before with smaller documents so I assume that either Google Docs Writer is not yet capable of handling long documents having pretty nasty HTML code inside (see the point about the code listing below ) or there had been connection problems caused by server problems. So I guess if I am about to write another similar post I might want to try a desktop application such as OpenOffice (with Sun Weblog Publisher extension) or I might want to separate the a bigger topic into several smaller posts (which would probably the best). I shouldn't use the Styles "Header 1" or "Header 2" from Google Docs as they let to too big headlines in the blog po...

Have you ever considered mirroring/synchronizing your important files from your Mac to your Linux machine to decrease the risk of data loss because of a hardware crash? One very effective way to do this is using two open source tools available on your Mac and your Linux machine called rsync and ssh. This document will lead through the necessary steps. The main reason for this document was to have a reference for myself as it wasn't trivial. Maybe it can be helpful for others. As a precondition, it is assumed, that you have two computers that are connected via a network. I am using a Macbook with Mac OS X 10.4 Tiger and an Ubuntu PC with Ubuntu 7.10 Gutsy connected via a WLAN where I have verified all the steps. Some of the steps described are Mac / Ubuntu specific. Most information should be valid for other operating systems where ssh and rsync can be installed (e.g. other Linux distributions) but you might check out the distribution specifics if something should not work. ...