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Re: Verify the integrity of Debian CDs



On Sun, May 08, 2005 at 03:54:43AM +0200, Goswin von Brederlow wrote:
> 'dd if=/dev/cdrom of=iso' will do, if only you had the md5sum files.

No, it might not work. This can be a bit tricky because some CD recording
software appends a few sectors of zero bytes after the recorded image (e.g.
"cdrecord -pad"), which changes the length of the image on the burned CD. 
Also, "dd" sometimes has problems reading all the bytes, "cat" usually does 
better. Additionally, I read on the net that sometimes mounting the CD 
makes a difference.

Maybe the MD5SUMS files should include the length of each image? Also, as
the OP's request shows, maybe they should be kept for a couple of months.

For reading the CD and calculating the md5sum, I recommend:
 - mount /cdrom
 - cat /dev/cdrom | md5sum

If that doesn't work, you can still try:
 - mount /cdrom
 - Execute "df", take note of the "1K-blocks" value for the CD
 - dd if=/dev/cdrom bs=1k count=<1K-blocks-value> | md5sum

Cheers,

  Richard

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