Philippe Gauthier

Ubuntu Québec était au GeekFest

Sun, 06 Mar 2011 19:26:10 -0500

L'équipe d'Ubuntu Québec était présente au festival montréalais célébrant les divers aspects de la culture geek toute la fin de semaine du 5 et 6 mars. Nous avons été surpris par la très importante proportion des visiteurs qui utilisent déjà Ubuntu, ce qui nous a tout de même permis de faire connaître notre communauté Ubuntu locale. Surnommées les LoCo Teams (de l'anglais Local Cummunity) les groupes d'utilisateurs tels que le nôtre font partie d'un large réseau de soutien. Cette structure communautaire différencie les systèmes d'exploitations tels qu'Ubuntu des systèmes d'exploitation propriétaires et même des distributions qui ont un caractère plus commercial.

Le groupe Ubuntu Québec est représenté par son site web http://www.ubuntu-qc.org/ et fournit une liste de discussion (par courriel, mais aussi accessible sous forme de forum) et une interface de clavardage pour du support en ligne interactif.

Parmi les activités sociales d'Ubuntu Québec, deux événements nous attendent dans les prochains mois. Le premier est une rencontre à caractère plutôt technique qu'on nomme Global Jam. La seconde est la soirée de lancement de la prochaine version d'Ubuntu. Le GeekFest nous a peut-être permis de trouver des hôtes pour tenir ces activités. Pour se tenir au courant du lieu et de la date des événements, il suffit de s'abonner à la liste de discussion.

« Be careful what you wish for »

Mon, 24 Jan 2011 12:13:53 -0500

Lors du dernier Ubuntu Hour à Outremont, Christian « Mobidoy » a apporté des auto-collants qu'il a préparé à partir de l'image du billet précédent. Un pas de plus vers la domination du monde ! Photo par Fabian Rodriguez :

Est-ce que je peux avoir un pony ?

Wed, 14 Jul 2010 10:04:22 -0500

Tout a commencé sur #ubuntu-qc lorsque le groupe cherchait où se procurer des autocollants pour boîtier d'ordinateur qui affichent le logo Ubuntu. Éventuellement, la discussion en arrive à une requête très particulière :

 I want a sticker that says "Powered by Ubuntu, Coffee and Ponies"
 +1 from me for coffee and ponies!
 ponies?
 haha
 yup ponies
 omg
 Coffee is what keeps Ubuntu going and the Ponies make all the automagical stuff work :)

Allez hop ! La magie du pony s'est mise en œuvre et quinze minutes plus tard voici le résultat. Le fichier SVG peut être téléchargé directement ici-même sous la license CC du blogue.

Getting started with free and open source software

Tue, 04 Aug 2009 10:40:38 -0500

The magic behind free and open source software (or FOSS) comes from a few people who are freely giving to society part of their work. Free software often start as projects fulfilling a personal need, then a community may grow around the project because it seems useful to them. Some of these people may eventually contribute to the project. After the working product is released freely to everyone, it becomes difficult to define the bounds of the community gathered around the software because anyone can be part of it. There is an amplification effect caused by the very low barriers to the distribution of the software to whoever needs it. This amplification is what enables you to get and use this software free of change, and better yet, with almost no restrictions. You can read about the GNU General Public License to get a feel of the idea behind free software.

Find a partner or mentor

You can find by yourself a lot of valuable information from the Web or from books. Still, most people don't want to spend most of their free time on just making the system work, and you may also prefer to make fun and useful things with your computer. Like just said before, the concept of community is crucial to the existence of free software. If you start using free software with some friends or family, you are building a small community that can share ideas, solutions, and useful projects. For example, you could try to set up a remote backup solution for a few people you know, or edit a private web site for the family.

Get a GNU/Linux distribution

You can find an increasing number of free software that can run on non-free operating systems, but if you have the choice I would recommend starting with a complete GNU/Linux distribution. Distributions are large collections of software and the management tools that are necessary to configure a complete system. Every distribution includes the Linux kernel (the core software between the application software and the computer hardware), and the GNU subsystem (a collection of common tools to manage files, programs and data), hence the name GNU/Linux. Distributions come with a default setup (or a choice from a few options) that you can adapt to your needs by using the management tools. A very popular distribution is Ubuntu. You can even try the distribution by starting the computer with an Ubuntu CD-ROM before installing it to your computer.

Real world example

The free software universe is not very different from the academic and scientific communities. There is of course a very broad yet common goal of making the world a better place by understanding it and making small but essential contributions. No scientist is really working alone, and the collaboration with other people and groups is necessary to succeed. The seeming compatibility between the free software and the scientific philosophies results in a large number of important scientific software projects being free. Here is a list of links and example free software projects:

A list of free software for the Mac (non-free, of course!) with a scientific bias.
The Python programming language, which is increasingly used for scientific work along with the SciPy software.
The LaTeX project, ubiquitous in scientific publishing.
The CERN software libraries.

More about free software

Enabling the Marvell SATA controller on an ASUS M2V motherboard

Thu, 29 Jan 2009 12:45:10 -0500

The computer running the deuxpi.ca domain had an extra hard disk installed since last November but I did not have a chance to use it because I didn't have a SATA cable for it. The disk was finally connected yesterday. However, the system did not recognize the disk. Also, the kernel was using a driver named "pata_marvell" (thus not, for example, "sata_marvell") for the controller.

After some research on the Internet, I found that the kernel loads the ahci driver which then delegates to the sata_marvell driver in order to support legacy PATA drives on this controller. Alan Cox introducted a kernel option to prevent this default behavior so the ahci driver would be used to drive the SATA ports. In my case, the Marvell controller is used only for SATA. See the thread for some history about SATA support for the Marvell 88SE6121.

To use this kernel option on a Ubuntu system, edit the grub configuration:

sudo gedit /boot/grub/menu.lst

Add ahci.marvell_enable=1 to the line of standard kernel options. For example:

# kopt=root=/dev/mapper/vg0-root ro ahci.marvell_enable=1

This line may be slightly different on another system depending on the partitioning scheme. Save the file, run sudo update-grub, and reboot the computer for this option to have effect.

Edit: See the Debian wiki page about enabling support for the Marvell SATA controller using possibly a better method.

« Chilling effects »

Mon, 27 Oct 2008 19:19:57 -0500

L'accusation de diffamation implique certainement un équilibre entre la liberté d'expression et la droit à sa réputation. En général, on s'attend à ce qu'il y ait injustice lorsqu'il y a une volonté de créer du tort.

Dans le cas des Éditions Écosociété, il est très difficile de justifier le bâillon (voilà je l'ai dit) que veut lui imposer Barrick Gold. La volonté de cette dernière est probablement discréditer les auteurs de Noir Canada, puisqu'il lui semble beaucoup plus facile d'écrire une mise en demeure qu'une réponse critique valide. Toute cette mauvaise publicité à été générée par les attaques légales de BG elle-même bien plus que par la publication du livre. Bref, il ne faudrait jamais se gêner de dénoncer ceux qui exploitent les faiblesses des systèmes juridique et économique; je me permets ici de reproduire le plus récent communiqué d'Écosociété :

Playing Loki's SMAC safely on recent systems

Wed, 20 Aug 2008 20:53:13 -0500

The computer strategy game Alpha Centauri (SMAC) keeps getting older and is not maintained since the company having the rights -- Loki software -- closed its doors, and the source code to the program is not by any means available to the public. It crashes easily for many reasons, but mostly for incompatibilities with the recent sound and graphic architectures. This is a game that I still enjoy from time to time when I feel very lazy. I get discouraged easily when the program crashes, leaving the screen resolution in a different setting, a few times in a row.

A large number of recent Linux installations have graphic features activated from an extension called Composite. This extension allows to create visual effects that are used in software such as Compiz and Beryl. However, SMAC is completely incompatible with the Composite extension, resulting in a crash shortly after the game starts (when the capsule lands, and the first base is founded). The usual workaround is to disable the Composite extension by adding a configuration option for the Xorg server, but doing this will prevent visual effects to work.

A different option is to use an embedded X server that will be only used for displaying the game. I use Xephyr, which can be launched by using the command

Xephyr :1 -screen 800x600 -extension Composite

Note that we can disable the Composite extension for this X server only. To launch SMAC, I have to specify the display to use. In the current example, Xephyr will create an X server as display :1.

DISPLAY=:1 smacpack

You should now see SMAC running in the Xephyr window.

Owww! It's hot in here!

Sat, 28 Jun 2008 21:18:17 -0500

I checked the current weather on the Web to make sure that the very high humidity was not a product of my imagination. Some clothes from this morning's laundry have been hanged but at this rate they are not even close to be dry until tomorrow. Environment Canada confirms: the air is over 90 % saturated with humidity and humidex is 29.

What really is humidex? I knew that it was supposed to represent the perceived temperature, but I clicked on the link for more information. It finally reveals that the formula does not have a strong physical basis. This empirical formula essentially is H = T + (e − 10), where, T is the temperature in degrees Celsius and e is the vapor pressure in mbar calculated from the dew point.

The site also offers a program named Chilldex to calculate the humidex and relative humidity based on the temperature and the dew point, but only if you run Windows... Ha! Let's use our mad Python skillz and create our own tools! Don't hesitate to modify and share.

humidex.py

windchill.py

(It will also spare you having to look at a picture of mounted police...)

Édition : Lire la critique de Miguel Tremblay Du refroidissement éolien et du facteur humidex (le ridicule a une température)

Rsync on Windows sanity

Wed, 25 Jun 2008 13:50:41 -0500

While I was trying to synchronize a music library between the Linux host and a Windows machine by using rsync (cwRsync, to be exact), I realized that most of of the directory and file names were scrambled, or displayed long strings of question mark characters. There is a --iconv flag to rsync I though of using so I started to search the Web for the details. Some mailing list from a year ago suggested using a Unicode-aware version of the Cygwin DLL. The site seems to be up-to-date with the current Cygwin thus I downloaded the new library and moved it to the cwRsync bin directory. It works! You can download the patched Cygwin library here.

Now the remaining problems are synchronizing files and directories with characters that the archaic Windows shell does not accept and Cygwin still doesn't process directories with more than 260 characters...

Edit: The limitation of 260 characters exists because Cygwin attempts to support the old non Unicode-aware versions of Windows. One day this may change. Also, there is a branch in rsync code that would allow the characters in the file names to be translated. A patched binary of rsync is available on the receiver side, but I don't have enough motivation to build a patched version on the Linux server side right now. Shame on Windows for bad POSIX support...

Shell history statistics meme

Thu, 17 Apr 2008 16:15:07 -0500

What now, dude? history | awk '{a[$2]++}END{for(i in a){print a[i] " " i}}' | sort -rn | head
200 sudo
182 ls
90 cd
62 vi
52 mv
43 java
38 eyeD3
33 tail
25 javac
21 ~/embedcover

Looks like I spend most of the time at the console organizing the music library (and breaking the computer--look at all those sudo and vi...)

Installation de Ounk sur Ubuntu 64-bit

Fri, 14 Mar 2008 13:44:00 -0500

Mise-à-jour : Il semble que Csound vient d'atterrir sur Ubuntu Hardy aujourd'hui (12 avril) ce qui évite de faire plusieurs des détours décrits ci-dessous !

Voici un résumé des opérations que j'ai du effectuer pour pourvoir installer l'interface Ounk sur un système Ubuntu 64-bit. Pour commencer, la difficulté vient du fait que Csound 5 n'est pas disponible. Toutefois, l'équipe de Debian-Multimédia travaille à créer un paquet qui devrait éventuellement faire son chemin jusqu'à son inclusion dans Ubuntu.

Pour obtenir le paquet actuel, il faut ajouter le dépôt de Felipe Sateler aux sources de logiciels. La ligne APT est :

deb http://felipe.sateler.com/debian unstable main

De plus, il faudra inclure le dépôt de Debian instable (sid) pour satisfaire les dépendances :

deb http://ftp.us.debian.org/debian sid main

Après avoir rechargé la liste, le paquet csound devrait être disponible dans la section Multimedia dans Synaptic. En le sélectionnant pour installation, les dépendances devraient être ajoutées automatiquement. Puisque qu'on utilise à ce moment le dépot de Debian instable, on évitera d'installer d'autres paquets. Après cette installation, il est fortement recommandé de désélectionner le dépôt de Debian dans la liste des sources.

Une fois cela fait, on peut en profiter pour installer les dépendances de Ounk : alsa-oss libportmidi0 libfluidsynth1 python-wxgtk2.8 svn.

Pour télécharger Ounk, il est plus facile d'utiliser une fenêtre de Terminal. Dans cette fenêtre, on peut aller demander la plus récente version en lançant la commande :

svn checkout http://ounk.googlecode.com/svn/trunk/ ounk-read-only

Subversion (svn) est un logiciel qui permet gérer le développement d'un logiciel en conservant un historique de toutes les versions des fichiers de code. Ici on demande d'extraire la plus récente version qui sera copiée dans un nouveau répertoire ounk-read-only. Pour mettre à jour les fichiers déjà obtenus, on peut se déplacer dans le répertoire et lancer

svn update

On peut maintenant lancer Ounk en se déplaçant dans le répertoire ounk-read-only et exécuter le programme :

python Ounk.py

Synthesizer tuning

Mon, 19 Nov 2007 13:19:20 -0500

A typical modular synthesizer is not limited to a number of fixed pitches, but can generate sounds in a very wide range of frequencies. However, if one needs to play the synth much like any other standard Western musical instrument, it will need to be tuned. The pitch relations between notes are generally handled by a MIDI to control voltage (CV) converter, or a quantizer. Tuning is usually performed by playing a note — in our case this is standard A above middle C, or A-440 — on a keyboard and turning on an oscillator with a constant reference pitch, like a virtual tuning fork. The main oscillator is tuned when no beats can be detected.

In my synthesizer, I now need a precise reference oscillator. There is a design by Dave Brown using the timers of a small AVR microcontroller to create a very accurate square wave. This signal is then transformed into a pure sine wave by a very sharp low-pass filter that removes the overtones. Dave does not publish his code on his page but even if I could get help if I asked, I'm reading the ATtiny25 datasheet and doing it the hard way.

The microcontroller has two timers that can be run from an external clock. There is a prescaler circuit that will increment the timer counter every power of 2 clock ticks up to 256 ticks per count. The idea here is to use a clock frequency that when divided by the prescaler will produce a timer very close to a multiple of 440 counts per second. Dave found that a clock running at 5.0688 MHz divided by 11520 is a very good approximation. The counters are limited to 8 bits (256 values). So the 5.0688 Mhz clock divided by 64 runs the counter at 79.2 kHz. If we count up to 180 to start a new pulse we get exactly 440 Hz.