Getting started with the new Raspbian "wheezy" image

Today the foundation announced the release of the new recommended SD card image for the Raspberry Pi, the “Raspbian” build of Debian “wheezy”. Until today there were several Debian based images in circulation, and pros and cons of each, as I discussed in a previous post. As of today, it is clear that more or less everyone should be running the official Raspbian image unless they have a very good reason not to.

After downloading the image, I installed it (from Ubuntu) on an SD card with:

% unzip 2012-07-15-wheezy-raspbian.zip
% sudo dd bs=1M if=2012-07-15-wheezy-raspbian.img of=/dev/mmcblk0
On the first boot, the “raspi-config” script runs, allowing a bit of customisation. If your SD card is bigger than 2GB, you can expand it. You can check the locale (defaults to UK), the RAM split (I have as much as possible for the CPU), enable SSH, configure desktop on boot (not for me), etc. When done, just finish and re-boot. This was much less buggy than the version on the wheezy beta, but there are still some disconcerting pauses.

 

On reboot, you can SSH in from a remote machine, which is how I mainly use mine. I then installed some essential (for me!) software:
% sudo apt-get install gsl-bin libgsl0-dev openjdk-6-jre
and then was ready to go. In a previous post I discussed floating point performance of the Pi, and wanted to check that was good on this image too. In the linked post I explain that my C test code ran in 20 minutes on the wheezy beta, but in 2 minutes 10 seconds on my experimental raspbian image (using the -O3 flag to gcc).

 

On the new raspbian image, the same code takes 2 minutes 45 seconds with the -O3 flag, and 2 minutes 30 seconds with the -O2 flag. This is a bit slower than the experimental image, but still an order of magnitude faster than the wheezy beta. I’m not sure why the official image is slower than the experimental image I was using, but it’s probably that I was using gcc 4.7 on the experimental image and gcc 4.6 on the newly released image, which ships as default. Despite this, the new raspbian image is a massive improvement on all previous images suitable for general use.

 

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darrenjw

I am Professor of Stochastic Modelling within the School of Mathematics & Statistics at Newcastle University, UK. I am also a computational systems biologist.

One thought on “Getting started with the new Raspbian "wheezy" image”

  1. UPDATE: I figured out the main source of the relative slowness of C code on the official Raspbian image relative to the experimental version I had been using. The experimental version was clocked at 800 MHz, whereas the official image is clocked at 700 MHz. Just comment out one line in /boot/config.txt and reboot to over-clock the official image at 800 MHz. Then the code runs almost as fast as I’d reported previously – around 2 mins 12 seconds (using either -O2 or -O3). Mystery solved!

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