Ubuntu 12.04 stops booting (b43 wifi problem)

I had problems installing Ubuntu 12.04 on my Dell Latitude D410 laptop. As it turned out it was because of the b43 wifi card. But let’s see the story step by step.

First, I couldn’t install the system from the normal install CD. The boot process simply stopped. So I downloaded the alternate CD. The installation went fine but when I rebooted the machine, it froze again… WTF? I got the following error message:

[ xx.xxxx] b43-phy0 ERROR: firmware file "b43/ucode5.fw" not found
[ xx.xxxx] b43-phy0 ERROR: firmware file "b43-open/ucode5.fw" not found
[ xx.xxxx] b43-phy0 ERROR: You must go to http://wireless.kernel.org [snip] read all the instructions on this website.

OK, so the firmware of the wifi card is missing. Let’s disable the wifi then. The following line should be added to /etc/modprobe.d/blacklist.conf:

blacklist b43

Here is how I did it: start the system with a 11.10 live CD (which doesn’t freeze), mount the root partition of the laptop, then modify the blacklist.conf file.

After reboot, the system didn’t freeze but, obviously, I had no wifi. Connecting a cable, I could install the following package:

sudo apt-get install firmware-b43-installer

Edit blacklist.conf again and enable b43 (put that line in comment). After restart I had wifi.

Tips from here: 1, 2.