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Re: CD/DVD Verify

Jonathan Allen wrote:
Paul Howarth wrote:
You could read back the data from the CD device using dd and then compare what you get back with the original ISO.

Thank you for the suggestion.  I just tried:

   # dd if=/dev/cdrom of=file

# dd if=dev/cdrom of=file bs=2048

and got a clutch of errors like:

   hdc: command error: status=0x51 { DriveReady SeekComplete Error }
   hdc: command error: error=0x50 { LastFailedSense=0x05 }
   ide: failed opcode was: unknown
   end_request: I/O error, dec hdc, sector 1904, 1912, 1920, etc in turn

What does that mean ?  The result produces a file 901120 bytes long, when
the original ISO file is 987136 bytes long, but at least at the front they
look pretty identical to 'od -c'

When the drive is mounted, all the files on the CD seem OK and don't
generate any media errors.

Given that the length of the resulting file is *less* than that of the original ISO, I suspect that there is a problem with the recording. If you got a resulting file that was *bigger* than the original ISO then that might not be an issue, as you could have read back some of the lead-out data after the end of the filesystem; as long as the files are identical up to the length of the original ISO, all should be OK but that's not the case here.


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