[conspire] kernel crash reported // for wifi ?

[Rick Moen]

Quoting Ken Bernard (kenbernard at gmail.com):

> Rick thanks for the information, I may reinstall Centos in order to correct
> this problem. I assume that I will have to completely replace my OS for a
> reinstall to  correct this kind of issue. Which means (to me) that I'll
> find myself with one or another new issues to deal with at that time.

If I might make a suggestion:

Get a composition book or legal pad.  Starting with your initial
installation of an OS, take notes on it about particular things you do,
problems you solve, configuration items you tweak, essentially all the
lessons you learn and significant system changes you perform.  You can
include the partition layout you specify in the installer, what package
sets you choose in the installer, and what packages you later add using
'yum' (this being CentOS) because you figured out you needed those, too.

That composition book or legal pad will be a life-saver on the evitable
day, later, when you wish to reinstall for any of a number of reasons:
on account of you having made an error with root authority that messed
up your system, on account of hardware failure (e.g., dead hard drive),
on account of it being sometimes easier to install a major OS revision
from scratch than to run an upgrader program, on account of switching
from one distro to another, or just because you've decided to re-do your
system and wish to start over.

This is standard advice that I try to give to all new Linux users.  One
of the additional side-benefits of reinstallation is that matters that
were unclear or were all a blur of technical detail you didn't fully
understand the first time will be much more easy to grasp and do right
when you do a reinstallation by yourself at your own speed, with the
help of notes from the first time.

> So 1st I'll look at *modprobe* and *iwconfig* as you point out. Hopefully I
> can then just uninstall the problem driver in Madwifi.
> 
> Am I correct in assuming that I probably don't need, or even want, both
> wireless card drivers on my (laptop's)system at the same time?

Correct.

In fact, if you know you have two drivers that you have good reason to
think might be interfering with each other (and that's very credible and
likely with madwifi and ath5k, since the latter's a successor to the
former), the kernel provides a mechanism for disabling particular kernel
modules in the form of the 'blacklist' directive to modprobe.

Each distribution is a little different in where the conffile is for
this, but it'll be either flat textfile /etc/modules.conf or a tree of
textfiles in /etc/modprobe.d/ or something like that.  Anyway, you do it
by adding lines to a textfile parsed by modprobe at startup like this:

blacklist ath_hal
blacklist ath_pci

There might be more parts of madwifi than just those two; I really am
not sure.  You can look through the output of 'lsmod' to see if you can
spot other relevant modules.

You should realise that blacklisting of modules (instructing modprobe
not to load them in the future) takes effect at subsequent reboots, not
in realtime.

If you wish to unload a module from the running kernel as well, use
modprobe directly:

modprobe -r ath_pci
modprobe -r ath_hal

The '-r' stands for 'remove', causing modprobe to do the opposite of the
operation it would otherwise perform.

Anyway, again, if you are reinstalling CentOS, I would strongly suggest
that it be CentOS 6.2 rather than the existing 6.0.