11.01.09
Webtip - 1. November 2009
Ever heard about the “Busy Beaver Problem”? Interesting introduction and visualization with lots of source code (Python, C++, Perl)
catonmat.net: The Busy Beaver Problem
10.18.09
Migrate trac-0.11.x from Debian Etch to Lenny
Since I was using the nice FineGradePermissions feature of the trac 0.11 release, and Debian was only providing trac-0.10.3 in Etch, I had a custom trac installation running on my Etch server. For migrating to Lenny you would normally think that it’s enough to just copy your project directory to the new installation. Unfortunately this results in a nasty error message:
DatabaseError: file is encrypted or is not a database
Hmn, so let’s check the trac migration guide which advises you to first export the sqlite database with sqlite3 in a plain SQL file. Not much luck here either, the result is an empty database:
# sqlite3 trac.db .dump
BEGIN TRANSACTION;
COMMIT;
The reason is the trac installation in Etch was using the python-sqlite-1.0.1 back-end which uses the SQLite 2 format while in Lenny there is python-pysqlite2-2.4.1 which only knows about SQLite 3.
The conversion from SQLite 2 to 3 can be done by first exporting the database with the sqlite tool and then re-importing it with sqlite3:
# sqlite trac.db .dump | sqlite3 trac3.db
More infos about this can be found at the trac upgrade notes from 0.8.x to 0.9.
Finally your trac installation should work again as usual.
10.16.08
Using vanilla kernel to run as ‘paravirt_ops’ Xen domU
Xen is nowadays a widespread approach to run virtual hosts. Thanks to its flexible configuration it’s not only possible to run virtual Linux hosts but nearly any operating system that is compatible to the Xen hypervisor machine architecture will possibly run as guest host. The Xen paravirtualization Read the rest of this entry »
04.23.08
Virtualized Animal Testing
Virtualization is not only a major topic in computer industries, but lately also in medicine. A Taiwanese laboratory introduced a “3D-virtual guinea pig” system for drug testing. And they even say “such a process would be able to replace some live animal experiments”.
You don’t believe me… read yourself:
www.chinapost.com.tw: ‘3D virtual guinea pig’ to be used for drug development
12.03.07
Manufactured Landscapes
Last week I went to cinema once again. In the tiny Kellerkino they showed the documentary “Manufactured Landscapes”. It is definitely a movie that should be seen by everybody.
The Canadian photographer and cameraman Edward Burtynsky attracted a lot of attention by his longterm work about how mankind changes the natural landscapes. The movie “Manufactured Landscapes” is showing us how industrialization in China looks like. He did choose China because it more and more becomes the factory of the world with all its negative consequences.
But compared to the movie “An Inconvenient Truth” by Al Gore about the global warming this movie does not rate the human acting. “Manufactured Landscapes” does not explain or discuss the destruction of nature it only shows it. Exactly this neutrality of the film-makers does lead to a speechlessness. You cannot totally accuse what you see because we depend on it and we provoke it with our economy. But on the other site it irreversibly destroys what has been on earth a long time before mankind.
The mixture of pictures and videos is underlaid with cold music and industrial noise. Sometimes there are short interviews, for example with a Chinese girl who assembles about 400 fuses a day, since six years. Or with an official of a coal mine trying to prevent the artist from filming their facility. You see the construction site of the Three Gorges Dam and the people destroying their own houses because their city will be flooded by this project. You see girls destructing our Computer waste for regaining the materials. But they cannot drink their ground water anymore because it is full of heavy metal residues. The movie shows the city of Shanghai which has to assimilate an increase in population of more than a million people per year. These are definitely other dimensions than we can even imagine here…
If I made you curious now you can watch the trailer of “Manufactured Landscapes” online.
What finally made me writing this article are some recent news about the Three Gorges Dam. First there was a video from National Geographic about landslides threating Chinese farmers. There they were still talking about a threat but today in the news there was already reported about a big landslide killing 34 people in the region of the Three Gorges.
Did you see the movie? Can we continue our extensive life forever? Can China handle this big challenge? Discuss it in the comments…
11.17.07
What is your Open Mind Index?
I like statistics. Not really when it is about calculating them but when it is about studying them. Of course first af all when there are statistics about myself. Gaming statistics is the one thing and statistics about music the other. last.fm provides me since one and a half year with hit lists from what music interprets, tracks and albums I am listening on my computers. I already had a lot of ideas about how this statistics collection could be expanded but others already did it.
Check out musickum.com: Open Mind Index Generator, enter your last.fm buddy name and let you show how open-minded you are when it’s about listening to music. You can compare it with others from same country or with same music taste.
For example here my last.fm OMI:
As you can see is my index about 104. The mean index of the people using this tool was 94. The interesting thing is for example that the mean OMI for people mainly listening to music tagged “Hip-Hop” is only about 85! Wow, what’s wrong here? Did hip hop once grew up from many different directions of music and ideas for ending here? Or men are with a mean index of 94.76 more open minded than women with 92.90. How can we read this?
There are many other interesting things that you “could” interpret from these numbers. But already our maths professor said: “Don’t trust statistics when you didn’t fake it yourself”.
Now let’s give me your OMIs… Who is the most open minded here?
10.03.07
Gentoo: QEMU in 32bit Xen environment
Recently I wanted to set up a testing server for the different virtualization techniques for Linux. For this I have an Asus P5LD2 mainboard with an Intel dual core Pentium D 3,2 GHz which supports the Virtual Machine Extensions (VMX). Thanks to this I can compile Xen with the ‘hvm’ USE-flag and run fully virtualized guest operating systems on my Xen supervisor. This means I could run nearly every i386 compatible operating system (even Windows 
) in my Xen environment. Without such hardware every guest operating system has to have a Xen enabled kernel.
Another approach with the same result is the open source project QEMU. Its abstraction level is higher than with Xen and it can even emulate different target architectures from your current x86 host. So far x86_64, ARM, SPARC, PowerPC, MIPS and M68k target systems are supported. Its guest operating system does not need any single change to run on QEMU. This makes it very comfortable to test new live CDs or operating system images. But it is not so trivial to setup QEMU and Xen together on a Gentoo machine.
How to setup QEMU on 32bit Gentoo in Xen dom0?
If you compile Xen on a 32bit host you have to add ‘-mno-tls-direct-seg-refs’ to your CFLAGS. That is because the glibc TLS library is implemented in a way that will conflict with how Xen uses segment registers. For compiling the non-patched QEMU 0.9.0 you have to use a gcc version 3.x. The nowadays default gcc 4.x is not yet supported. After several compile failures I finally found to setup QEMU the following way:
1. For compiling gcc-3.x remove the ‘-mno-tls-direct-seg-refs’ from /etc/make.conf and set the ‘nossp’ and ‘nopie’ USE-flags. Otherwise gcc or later qemu will not compile.
2. Switch to gcc-3.x before compiling qemu-softmmu, qemu-user and qemu. In my case it’s: gcc-config i686-pc-linux-gnu-3.3.6
3. Check your CFLAGS again because the optimization flags for gcc 4.x are not always backwards compatible to gcc-3.x. In my case the make.conf looks like this:
# gcc-3.x
CFLAGS="-march=pentium4 -O2 -pipe -fomit-frame-pointer -mno-tls-direct-seg-refs"
# gcc-4.x for compiling gcc-3.3
#CFLAGS="-march=prescott -O2 -pipe -fomit-frame-pointer"
# gcc-4.x
#CFLAGS="-march=prescott -O2 -pipe -fomit-frame-pointer -mno-tls-direct-seg-refs"
4. Now you can compile QEMU. Do not forget to switch back to your original CFLAGS and gcc-4.x after successfully emerging QEMU. I recommend to you to also build the QEMU kernel accelerator module kqemu which has to be compiled with the same compiler as the kernel itself.
Now Xen and QEMU are able to run whatever operating system image you give them. Have fun with playing around…
Continuative links:
09.26.07
DokuWiki - A small Wiki for everyday use
For organizing our move to the shared flat I was looking for a small, simple to use Wiki for collecting ideas and coordinating our flat inventory. After a little search I found DokuWiki. It can be easily installed by every Linux distribution’s package manager. Unfortunately the stable Debian package was not the newest version and annoyed me with banners that there are some upgrades available. So I tried again with the newest version from the developers site. After unpacking, the directory has to be made accessible through your Web server and after running the install.php where you actually only create the administrator user, the Wiki is already prepared to use. In the default configuration there is no database needed. But the strength of this Wiki is that it can be expanded by more sophisticated configurations using MySQL or an LDAP back-end for user administration. The syntax is quite simple and similar to other Wiki systems. Also my friends were surprised by the usability of this piece of Open Source software. So if you are planning to use a powerful but simple Wiki software, keep an eye on DokuWiki.
09.24.07
My first own flat
After nearly one year of searching an appropriate flat it succeeded. You cannot imagine how hard it is to get a flat near the university district Länggasse in Bern. Ether they do not have a balcony or they are much too expensive and they do not want students or, when you finally found one you like, there are at least twenty other parties having the same impression. But now, finally, I got the keys to my first own flat this weekend. Unfortunately it is not near the university but just next to the famous bear pit near the old town. Haha, I cannot wait to say “good night” to the bears before going home. Admittedly it is not only my flat. I share it with two colleagues who I already know since several years or even since the high school time. Soon I do not have to walk home for more than forty minutes when I once again missed the last bus. But I do have to wash for myself, cook for myself, care for myself… I am looking forward. Within the next few days I will always take some stuff into the new flat (beer is already cooled in the fridge since we received the keys ) and when there is eventually Internet available everything will be ready to move. Life, i am coming…
09.21.07
wow, how people can find this site ;-)
What interesting pages link to ganto’s Blog?
And once more I became weak because of a google thing. It’s the google webmasters tools. You can dig in a lot of google records of your Web site. Maybe more about this later…
Here a first nice “partner” site: