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Re: USB disk shows up late at boot

On Tuesday 22 December 2009 07:48:05 Hugo Vanwoerkom wrote:
> Andrew Reid wrote:

> >   It's likely the devices aren't being recognized in the initramfs --
> > possibly they require kernel modules which are not present by default.
> But I would think that to be the case of the custom kernel, not the
> Debian kernel. The small custom kernel recognizes both USB drives, the
> Debian kernel recognizes only one of them.

  There's no obvious reason (to me) why it should go one way
or the other.  Both custom kernels and the initramfs want to be
small, so they can both be selective.  I can easily imagine a scenario
where, for convenience, you include all USB mass-storage drivers in 
your custom kernel, but the initramfs decides USB might not be needed
at boot-time, and leaves a few out.

  I don't actually know, one way or the other, I'm really just
guessing at this part.

> >   If you know which modules drive these devices, add them by name
> > to /etc/initramfs-tools/modules (one module per line, I think), and
> > re-generate your initramfs with update-initramfs.  This should allow
> > the udev scan in the initramfs to see the devices, and set them
> > up earlier.
> I have no idea, except to compare both initrd images.

  One option is to compare the "dmesg" lines from the two kernels, 
they generally report what they're doing during the device scan.

  Another option is to query the live device when it's plugged in
to the system, and ask it what module is being used.  I don't actually
know how to do this, but I'm pretty sure it's possible.  There are
lots of udev tools, maybe one of those.

				-- A.
Andrew Reid / reidac@bellatlantic.net

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