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Re: Media Check errors on Fedora Core 6



On Fri, 27 Oct 2006, Deron Meranda wrote:

On 10/27/06, Thompson Freeman <tfreeman intel digichem net> wrote:
I have downloaded the cd isos for FC-6, and the sha1sums of
the images test as good. I have burned to cd two complete
sets of cds, and gotten one cd to pass the media check
step. _Everything_ else fails, and fails multiple times.

How are you burning the CDs?  It is most likely caused by
the lookahead buffering used during the write process (or something
like that, I don't fully understand).

If you're using cdrecord, try adding the options "padsize=63s -pad -dao".
It has worked for me.  Such as something like:

The solution turned out to be found earlier - run with the ide=nodma command line. Everything turns happy then.


$ cdrecord -v padsize=63s -pad -dao dev=ATA:1,1,0 FC-6-i386-disc1.iso


As a side issue, how would I get the sha1sum of the burned
cd? I believe that should remain the same as the image
file, or am I completely a sea?

I've not found an easy way for this either, as you need to ignore
any padding bytes at the end (which don't matter).  So it's a
multistep process where you read the raw bytes from the CD, truncate
it to the correct length, and then SHA that.  Something like this
sequence where the CD is read into a file called "x.iso"...

$ readcd dev=ATA:1,1,0 -f x.iso

$ isoinfo -d -i x.iso
...
Logical block size is: 2048
Volume size is: 346084

$ echo $(( 2048 * 346084 ))
708780032

$ dd if=x.iso bs=2048 count=346084 status=noxfer | sha1sum
cc503d99c9d736af9052904a6ab14931b0850078  -


Ok. Now that is a little bit ugly. Doable, scriptable, but not pretty. I think I'll pass on that idea.

Still, I really appreciate your time to write it out. I will definitely save it against future need. Thanks.


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