Technology weblog

Friday Sep 03, 2010

Why CentOS is evil

Recently, I discovered that CentOS is in fact evil. Why?

  • Their current kernel version is ... 2.6.18. This kernel was released in ... September 2006!
  • The old 2006 kernel is patched with hundreds of RedHat patches. Consequence: when running Selenium with Java and Firefox, FireFox processes aren't properly closed, eventually clogging up all system resources and the machine starts trashing.
  • Trying to install a plain recent Linux kernel turns out to be (close to) impossible (actually, it is strongly advised against, what the heck??).
  • The CentOS installer "yum" has a (very) outdated notion of the versions of most software packages that can be installed.
  • Last but not least, you are stuck with the horrible RPM package format: installing a custom (i.e. out of "yum's" scope) RPM often requires four additional other RPMs it is dependent on, each of which in turn requires four more RPMs, leading to an combinatorial explosion of dependencies.
Basically, the whole CentOS distribution consists entirely of out of date software, which is at best almost impossible to upgrade. I'm really wondering why anyone would actually be inclined to prefer this distribution above e.g. Ubuntu or Gentoo Linux.

Wednesday Jun 02, 2010

Wireless tethering with WPA supplicant

Since my G1 phone has been rooted, I can use wireless tethering. However, initially I had difficulties configuring WPA supplicant to recognize the G1 tether, which apparently is running in ad-hoc mode. After setting ap_scan=2 in my wpa_supplicant.conf, everything started working flawlessly with the following configuration:


 # Keys specified without quotes are hex keys

Monday Apr 05, 2010

Flash builder Eclipse plug-in on Linux

For my new project, I was allowed to use my Linux laptop as development environment. The new project being an Adobe Flex project almost forced me back to the Windows platform, as Adobe does not make an Eclipse Flash Builder plug-in available for Linux. This post describes a successful effort to make Adobe's Flash builder available for Eclipse (Ganymede and Galileo) on the Linux platform.[Read More]

Monday Dec 14, 2009

Gentoo Linux on Asus UL-30A notebook

Recently I bought the Asus UL-30A ultra-portable laptop and installed (Gentoo) linux on it. Summarizing, installation of Linux on this machine makes it even more value for money. I also got Compiz Fusion running, which even makes Mac die-hards doubt their expensive alternative ;-)

Sunday Oct 18, 2009

Device driver check and report

I recently discovered this site, which allows you to copy and paste the output of 'lspci -n' in a textfield on the web page, and shows you which parts of your hardware are supported from which kernel version, like so:

lspci analysis.

Monday Dec 08, 2008

Problem starting Ganymede profiler under Gentoo

Recently I discovered that I could not start the Eclipse (Ganymede) profiler by right clicking on a Java application and selecting Profile As -> Java Application. The monitor tab in the configuration window would show: "The launch requires at least one data collector to be selected." On the Internet I found this post that suggested to look in my workspace/.metadata/.log file. Indeed, I found various entries stating "ACServer: error while loading shared libraries: cannot open shared object file: No such file or directory". The solution was an installation of lib-compat: emerge lib-compat solved the problem, even without a restart of Eclipse!

Thursday Jan 17, 2008


If you need to list the contents of your directories in such a way that they can seemlessly be incorporated into a presentation, the tree command is probably what you are looking for. After setting up a Maven archetype project, the tree command was used to generate the followiing output:

bash[572]% tree -F demo-app/
|-- pom.xml
`-- src/
|-- main/
| `-- java/
| `-- demo/
| `--
`-- test/
`-- java/
`-- demo/

7 directories, 3 files

What cannot be seen here is that even directory colors are seen, just like listing with ls.

Gentoo Linux users can easily obtain this tool using:

emerge -av app-text/tree

Sunday Jun 10, 2007

That useful rsync utility

Since some weeks, I own a housing for an external USB hard disk, and recently bought a 320 Gig hard disk to go with it for my backups. I didn't know 320 Gigs were that much though :)

Instead of all the hassle with DVDs (or even worse CDROMs), I now merely "rsync" my folders containing e.g. my pictures on a regular basis:

/usr/bin/rsync --verbose --progress --stats --compress --times --perms --delete -a \
srcDir/ /mnt/ext/partition2/destDir/

Actually, I already use rsync to backup this blog to the server of my provider. In this case, rsync seamlessly incorporates synchronization over SSH, see for example the following excerpt of my script that is started with cron every night:


RSYNC_COMMAND= "/usr/bin/rsync --verbose --progress --stats --compress --times \
--perms --delete -a -e ssh"

cd /tmp

# Backup Blog database
/usr/bin/pg_dump roller > rollerDB
/bin/bzip2 rollerDB
/bin/rm rollerDB.bz2

# Backup uploaded files
$RSYNC_COMMAND ssh /usr/local/apache-roller-3.1/webapp/roller/roller_data/uploads $BACKUP_LOCATION

Saturday Jun 02, 2007

USB Uno MIDI interface

A couple of weeks ago I bought a USB MIDI interface, one that is supported under Linux, of course.


Midisport Uno USB MIDI interface


It is the Midisport Uno by M-Audio. Finally I can play my favourite MIDI files on my digital piano (again) as well as record my playing with a sequencer using my laptop. Although it took me some time to get the Uno working under Linux, I am now immensely happy with it, since I normally never use Windows and I have Rosegarden to my avail. What an incredibly nice and feature rich open source MIDI program. The only scarce resource left now is my time!

[Read More]

Sunday May 27, 2007

Restoring boot loader after windows installation

If you install Windows on a computer that has Linux and the (Grub) bootloader already installed, you will see that the Linux bootloader has been overwritten during the Windows installation process. To recover, do:

  • Boot from your favourite Linux rescue CD / Knoppix distribution/ Other Linux live CD
  • If you forgot your harddisk lay-out, do fdisk /dev/hda and do 'p', to print the partition table. Exit with 'q'. 
Suppose the boot partition to be on /dev/hda6 and the root on /dev/hda7. Of course, your /boot may be located on your root partition too, in which case you just leave out the associated steps below.
  • Create a mountpoint, let's say mkdir /mnt/root.
  • Mount your partition: mount /dev/hda6 /mnt/root.
  • Change root chroot /mnt/root. If you have /boot on a separate partition, do mount /dev/hda7 /boot
  • Do grub-install /dev/hda
That should be all!

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