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Re: Can't mount CD/DVD drives

On Wed, Feb 15, 2006 at 07:20:53PM -0500, Carl Brown wrote:
> On Wednesday 15 February 2006 3:45 Pm, Austin Denyer wrote:
> > My feeling is along the lines of Carl's in that I think it is a udev
> > issue.
> I just found some strong evidence to support the initrd theory. As Erik suggested, I did:
> chmod 000 /lib/modules/`uname -r`/kernel/drivers/scsi/ide-scsi.ko
> then rebooted.
> Imagine my surprise when I saw:
> # lsmod | grep ide
> ...
> ide_scsi               18116  0
> ...
> When:
> # ls -l /lib/modules/`uname -r`/kernel/drivers/scsi/ide-scsi.ko
> ----------  1 root root 25892 2005-09-27 22:15 /lib/modules/2.6.12-1-amd64-k8/kernel/drivers/scsi/ide-scsi.ko
> This proves that the ide_scsi module is coming from somewhere besides /lib/modules/...

The initrd image of course.  It was copied in there by whatever initrd
generating tool you used.  Probably mkinitrd.  You could just do this:

add 'ide-cd' to /etc/mkinitrd/modules and then run 
'dpkg-reconfigure linux-image-2.6.12-1-amd64-k8' to recreate the initrd.

That will ensure ide-cd loads first, which should usually mean it will
grab the cd/dvd before ide-scsi can.  Then in the future it won't have
ide-scsi anymore.  It could even be that just recreating the initrd
while running 2.6.11 or older from before the initrd stupidly had the
ide-scsi added would also create a proper initrd again.

> In the past, and I'm sure someone will correct me if I'm wrong, 
> an initrd image was only required if the system booted from a SCSI drive,
> or had some other exotic arrangement. 

No it is required for any kernel where the root filesystem is on a
device that requires modules loaded to be present.  The debian kernels
are so modular and flexible (in different hardware they can support)
that they need modules loaded for all machines.  If you run then on a
system with no ide controllers, then it would not have any ide code
loaded at all.  Nice an efficient for all that way.

> (This system is booting from an SATA, if that makes a difference.)
> So if one is booting a system that should not require an initrd image, couldn't any
> initrd image be safely deleted, provided the appropriate edits were made to the grub menu file?

Well the sata drivers are also modular in the debian kernels, so you do
need an initrd.

> Or more to the point, why did the debian installer set up an initrd image if it was not necessary?
> Or if it was formerly required, but no longer required due to kernel changes,
> why was there no notification from the upgrade configuration process?

It was necesary is why it did it.

> It appears to me that we are indeed "getting hosed by silent changes".

Well you are getting hosed by a broken initrd tool that added ide-scsi
on a system where it shouldn't have.  It happened to lots of people.
Moving on to future kernels seemed to fix it for everyone else.

> BTW, the optical drives magically became mountable after a reboot, 
> but they are still acting a bit funny, and I have no idea what "fixed" them.
> They are still found at scd* and/or sr* for the moment.

Until you boot with an initrd that forces it to use ide-cd instead of
ide-scsi, it will act weird.  ide-scsi is broken.

Len Sorensen

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