Petter Reinholdtsen

Germany is a core area for the Debian Edu and Skolelinux user community, and this time I managed to get hold of Wolfgang Schweer, a valuable contributor to the project from Germany.

Who are you, and how do you spend your days?

I've studied Mathematics at the university 'Ruhr-Universität' in Bochum, Germany. Since 1981 I'm working as a teacher at the school "Westfalen-Kolleg Dortmund", a second chance school. Here, young adults is given the opportunity to get further education in order to do the school examination 'Abitur', which will allow to study at a university. This second chance is of value for those who want a better job perspective or failed to get a higher school examination being teens.

Besides teaching I was involved in developing online courses for a blended learning project called 'abitur-online.nrw' and in some other information technology related projects. For about ten years I've been teacher and coordinator for the 'abitur-online' project at my school. Being now in my early sixties, I've decided to leave school at the end of April this year.

How did you get in contact with the Skolelinux/Debian Edu project?

The first information about Skolelinux must have come to my attention years ago and somehow related to LTSP (Linux Terminal Server Project). At school, we had set up a network at the beginning of 1997 using Suse Linux on the desktop, replacing a Novell network. Since 2002, we used old machines from the city council of Dortmund as thin clients (LTSP, later Ubuntu/Lessdisks) cause new hardware was out of reach. At home I'm using Debian since years and - subscribed to the Debian news letter - heard from time to time about Skolelinux. About two years ago I proposed to replace the (somehow undocumented and only known to me) system at school by a well known Debian based system: Skolelinux.

Students and teachers appreciated the new system because of a better look and feel and an enhanced access to local media on thin clients. The possibility to alter and/or reset passwords using a GUI was welcomed, too. Being able to do administrative tasks using a GUI and to easily set up workstations using PXE was of very high value for the admin teachers.

What do you see as the advantages of Skolelinux/Debian Edu?

It's open source, easy to set up, stable and flexible due to it's Debian base. It integrates LTSP out-of-the-box. And it is documented! So it was a perfect choice.

Being open source, there are no license problems and so it's possible to point teachers and students to programs like OpenOffice.org, ViewYourMind (mind mapping) and The Gimp. It's of high value to be able to adapt parts of the system to special needs of a school and to choose where to get support for this.

What do you see as the disadvantages of Skolelinux/Debian Edu?

Nothing yet.

Which free software do you use daily?

At home (Debian Sid with Gnome Desktop): Iceweasel, LibreOffice, Mutt, Gedit, Document Viewer, Midnight Commander, flpsed (PDF Annotator). At school (Skolelinux Lenny): Iceweasel, Gedit, LibreOffice.

Which strategy do you believe is the right one to use to get schools to use free software?

Some time ago I thought it was enough to tell people about it. But that doesn't seem to work quite well. Now I concentrate on those more interested and hope to get multiplicators that way.

About two weeks ago, I was interviewed via email about Debian Edu and Skolelinux by Bruce Byfield in Linux Weekly News. The result was made public for non-subscribers today. I am pleased to see liked our Linux solution for schools. Check out his article Debian Edu/Skolelinux: A distribution for education if you want to learn more.

Recently I have spent time with Skolelinux Drift AS on speeding up a Debian Edu / Skolelinux Lenny installation using LTSP diskless workstations, and in the process I discovered something very surprising. The reason the KDE menu was responding slow when using it for the first time, was mostly due to the way KDE find application icons. I discovered that showing the Multimedia menu would cause more than 20 000 IP packages to be passed between the LTSP client and the NFS server. Most of these were NFS LOOKUP calls, resulting in a NFS3ERR_NOENT response. Because the ping times between the client and the server were in the range 2-20 ms, the menus would be very slow. Looking at the strace of kicker in Lenny (or plasma-desktop i Squeeze - same problem there), I see that the source of these NFS calls are access(2) system calls for non-existing files. KDE can do hundreds of access(2) calls to find one icon file. In my example, just finding the mplayer icon required around 230 access(2) calls.

The KDE code seem to search for icons using a list of icon directories, and the list of possible directories is large. In (almost) each directory, it look for files ending in .png, .svgz, .svg and .xpm. The result is a very slow KDE menu when /usr/ is NFS mounted. Showing a single sub menu may result in thousands of NFS requests. I am not the first one to discover this. I found a KDE bug report from 2009 about this problem, and it is still unsolved.

My solution to speed up the KDE menu was to create a package kde-icon-cache that upon installation will look at all .desktop files used to generate the KDE menu, find their icons, search the icon paths for the file that KDE will end up finding at run time, and copying the icon file to /var/lib/kde-icon-cache/. Finally, I add symlinks to these icon files in one of the first directories where KDE will look for them. This cut down the number of file accesses required to find one icon from several hundred to less than 5, and make the KDE menu almost instantaneous. I'm not quite sure where to make the package publicly available, so for now it is only available on request.

The bug report mention that this do not only affect the KDE menu and icon handling, but also the login process. Not quite sure how to speed up that part without replacing NFS with for example NBD, and that is not really an option at the moment.

If you got feedback on this issue, please let us know on debian-edu (at) lists.debian.org.