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Date: Wed, 16 Jan 2002 00:29:42 -0600
To: "Eric S. Raymond" <esr@thyrsus.com>, Rob Landley <landley@trommello.org>,
        Nicolas Pitre <nico@cam.org>, lkml <linux-kernel@vger.kernel.org>,
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Subject: Re: CML2-2.1.3 is available
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From: Peter Samuelson <peter@cadcamlab.org>
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[esr]
> The version I just released does exactly that.  Well, not exactly; it
> actually looks at fstab -- /proc/mounts gives you '/dev/root' rather
> than a physical device name in the root entry.

/etc/fstab is hardly guaranteed to be accurate either.  The kernel
mounts the root device based on its command line and any pivot_root()
calls you make, not based on /etc/fstab.

[In practice, I imagine most people don't lie to fstab.  The fsck init
script would get annoyed.]

But the horse's mouth, in this case, is /proc/sys/kernel/real-root-dev,
a 16-bit decimal int which represents a device number in
MAJOR*256+MINOR format.  There *may* also the 'root=' asciiz string in
/proc/cmdline, which will be a 4-digit hex number, but that is not
reliable - because of pivot_root() among other things.

On my system, real-root-dev gives 8453, which means /dev/hde5, which is
on ide2.  According to /proc/ide/ide2/config, it is a PCI device of
type 105a:4d30 [Promise Ultra100], so you can derive
CONFIG_BLK_DEV_PDC202XX as well as CONFIG_BLK_DEV_IDEDISK.

Peter
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