Re: [debian-knoppix] Problems with IDE HD after knx-hdinstall, that looks like a DMA problem

[Achim Unger <Achim.Unger@Ing-Buero-Unger.de>]

Hallo ,

thanks for all who helped detecting my problem. Most have probably deleted this thread, because it is ages ago:-)) I still could not tackle down that particular problem, but I made some odd experience with CDROM's in the meantime. Others are having some trouble as well, so I decided my eperience might be useful to others:

- Once a cdrom was producing errors, after reloading they disappeared. (Not cleaning, just open and close!)
- One set of cdrom looses its silver coating, one cd almost completely, after 3 Month of use!
- in the cdreader "dd if=/dev/cdrom of=/dev/null" produces errors, in the cdwriter it works nicely.
 
One possible explanation is a differently adjusted laser beams.

To compare a burned image to the original knoppix-image, boot it and do on the _mounted_ image:

	cat /dev/cdrom | md5sum 

and compare it to the ISO-Image somewhere:

	md5sum somewhere/image.iso

They should not differ.


I have written a small script, that does some ramtest, according to KK's recommendations:
#--------------------------------------------------
RAM=$(free | awk '/Mem:/{print $2}')
RAM=$(( $RAM+4096 ))
FREEDISK=$(df | sort -nk4 | tail -n1 | awk '{print $4,$6}')
DISK=$(echo $FREEDISK | awk '{print $2}')
FREE=$(echo $FREEDISK | awk '{print $1+4096}')
test   "$FREE" -lt "$RAM"  && (echo "NO FREE DISKSPACE FOUND"; kill $$)

echo "RAM: $RAM"
echo "DISK: $DISK"
echo "FREE: $FREE"

dd if=/dev/urandom of=$DISK/TMP.dd bs=1024 count=$RAM

ping -f localhost & 
ping -f localhost &
ping -f localhost &
ping -f localhost &
ping -f localhost &
LOAD=$( cat /proc/loadavg | awk -F"." '{print $1}')
while [ $LOAD -lt 20 ]
do 
        ping -f localhost &
        ping -f localhost &
        ping -f localhost &
        ping -f localhost &
        ping -f localhost &
        sleep 5
        LOAD=$(cat /proc/loadavg | awk -F"."  '{print $1}')
        echo ""
        echo "LOAD: $LOAD"
done
cp -p $DISK/TMP.dd $DISK/TMP2.dd
killall ping
echo "comparing ...."
diff $DISK/TMP.dd $DISK/TMP2.dd
test $? || echo "BAD RAMr!"
echo " remember: no messages are good messages ;-))!"

rm $DISK/TMP.dd $DISK/TMP2.dd

#--------------------------------------------------

> > > after installing knoppix 3.1 2003-03-28 on hd with knx-hdinstall at a
> > > friends computer, he SOMETIMES gets read errors and the filesystem gets
....
Klaus Knopper wrote:
> It may be a problem with bad RAM, that occures when writing data under
> high bus load (which can happen because of the decompression during
> knx-hdinstall). You could try the following to check for bad or
> overclocked RAM:
> 
> - Run several ping -f localhost &
> - Copy a large file (larger than your physical RAM), like in
>   dd if=/dev/urandom of=file1 bs=1000k count=500
>   cp file1 file2
> - Do a md5sum check on both files. If the checksums differ, exchange
>   your board or your RAM.

Thanx to all who have helped.

Greetings 

Achim

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