> From: "Ronald W. Heiby" <[EMAIL PROTECTED]>
> To: [EMAIL PROTECTED]
> Subject: Verify Written CD-R?
>
> Hello seawolf-list,
>
> I recently downloading a .iso file and wrote it using cd burning
> software to a CD-R. However, since the software I used was a new
> version that I'd never tried this on, I am left wondering whether it
> actually worked.
>
> I'm sure this is simple, but I'm looking for the command line that
> will verify the contents of the CD-R against the md5 checksum for the
> original .iso file. I've tried several md5sum command lines, and
> looked through CD burning FAQs, but have been unable to come up with
> the right magic.
>
You need the size in kbytes of the original ISO file or you can mount the
CD and get the size from "df /mnt/cdrom" (or whatever the mount point is).
Then divide the size in kybtes by 2 to get count of 2048 byte blocks and
run:
dd if=/dev/cdrom bs=2048 count=block_count | md5sum
Where /dev/cdrom is whatever your CD device file actually is and
block_count is the number you calculated above.
for example, ls on a seawolf disc1 iso file gives:
656764 -rw-r--r-- 1 rep 672518144 Apr 19 2001 seawolf-i386-disc1.iso
This would give a count of 656764/2 or 328382 kbytes, so you'd do:
dd if=/dev/cdrom bs=2048 count=328382 | md5sum
When you burn the CD, you should make sure you're using an option that
says something like "make CD from CD Image" as opposed to soemthing that
COPIES the ISO file ONTO a normal CD (ISO9660) file-system. You want to
do a bit-by-bit copy of the .iso file to the raw CD.
Presumably you want to do disk-at-once as opposed to track-at-once also.
Some people have been able to verify MD5 sums with "mdtsum /dev/cdrom", but
this doesn't work for me on any of the CDs I've tried. It may work only
for purple CDs written on odd days during even numbered hours of the day
or for people whose names start with a letter in the first half of the
alphabet.
pete peterson
GenRad, Inc.
7 Technology Park Drive
Westford, MA 01886-0033
[EMAIL PROTECTED] or [EMAIL PROTECTED]
+1-978-589-7478 (GenRad); +1-978-256-5829 (Home: Chelmsford, MA)
+1-978-589-2088 (Closest FAX); +1-978-589-7007 (Main GenRad FAX)
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