Image modules?

Rask Ingemann Lambertsen ccc94453 at vip.cybercity.dk
Sun Jul 5 21:06:45 CEST 2009


On Sat, Jul 04, 2009 at 08:45:12PM +0200, David Fokkema wrote:
> On Sat, 2009-07-04 at 17:52 +0200, Glenn Moeller-Holst wrote:
> > This is what I am not able to read anywhere:
> > *I actually do not know if I already having modules installed? How do
> > I test it?
> 
> Look in /lib/modules/<kernel-version>, or unpack the modules file and
> check. You'll find you already have it.
[snip]
> > *Why is there a separate file called modules? Why not include it in the image?
> 
> It _is_ included in the root image, as it lives in the root filesystem
> in /lib/modules. The thing is: if you decide to use that kernel but
> _not_ use that root filesystem (because you'd like to build your own,
> for example, or you just want to upgrade your kernel and _not_ your
> filesystem) you'll have to untar the corresponding modules into your own
> filesystem.

   Once you've extraced the modules into /lib/modules/<version>, do remember
to run (as root)

depmod -a <version>

because not all distribution do so during startup. Supposed the rootfs is on
an external card reader mounted on /mnt/flash, the depmod command becomes

depmod -a -b /mnt/flash <version> 

   For someone working on the kernel, modules are very useful because you
can test your changes simply with

rmmod <module>; modprobe <module>

instead of rebooting. 

   Some distribution (e.g. Fedora) ship a kernel image with only a few
drivers and generate a customized initial ram disk with modules during
kernel installation. So the same kernel build works across the supported
systems without being bloated by unused drivers.

-- 
Rask Ingemann Lambertsen
Danish law requires addresses in e-mail to be logged and stored for a year



More information about the community mailing list