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Date: Fri, 1 Apr 2005 22:01:04 -0800
From: Astrodog <astrodog@gmail.com>
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References: <f0111a98c01333b3c306c81d10294de4@khera.org>
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Subject: Re: Tyan k8sr lockups
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On Apr 1, 2005 8:26 PM, Doug White <dwhite@gumbysoft.com> wrote:
> On Fri, 1 Apr 2005, Gary Mu1der wrote:
> 
> > I have isolated the crash to the following dd command:
> >
> >       dd if=/dev/mem of=/dev/null bs=1024k skip=4040 count=1
> 
> Reading from random places in /dev/mem will cause unpredicatable behavior.
> Memory at that offset is in PCI memory-mapped device space, and reading
> from there may disrupt the PCI bridge, enable or disable interrupts, or
> worse.
> 
> --

I think the basic idea here is that dd'ing from /dev/mem may or may
not work, on any given hardware, and is certainly not reccomended. If
you want to test this "Safely", do an mdconfig, and dd onto, or from
the md device.