loading modules

Kevin Alm kevinalm at shenessex.heartland.net
Thu Feb 26 13:59:29 PST 2004

> <snip>
> > Without an initrd containing the ide-scsi module, a kernel line arg
> > hd?=ide-scsi will fail.
> > This is because when the kernel tries to
> > install ide-scsi support via the kernel line arg, the
> > /lib/modules/<version> filesystem usually isn't mounted.
> I am a little confused by this. I never expected the kernel to load the
> module at the time it encountered the kernel option.  I thought it was
> only there to keep the cdrom device from being claimed by the ide
> driver.  I assumed that when an application needed the cdrom then the
> kernel would load it.
hd?=ide-scsi is a directive to load the ide-scsi module. If it fails, the 
kernel will try to fall back to ide-cd. If ide-cd is compiled in then it will 
succeed with ide-cd locking out ide-scsi. (At least I've never found a way to 
get ide-cd to release a drive.)  This all happens before mounting the 
filesystems, so the /lib/modules/<version> isn't available, the only place to 
get kernel modules is the initrd. 

I had never heard of the ide-cd ignore trick. Using that, the kernel might 
autoload ide-scsi. But I suspect that ide-cd ignore is also an immediate 
command, and ide-cd might load instead, unless you manually modprobe ide-scsi 
first. (Or put it in the startup scripts.) The crux of the matter is that 
ide-cd/ide-scsi are a fairly low level part of the os. The kernel tries to 
grab the cd drives as soon as possible one way or the other, and doesn't want 
to let go.


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