cdrecord verify

[Sarantos Kapidakis]

Recently I found out that I must trust CDs less than what I used to!

How can I verify a CD against the iso9660 I used to write it ? The
cdrecord has no verify option. Is there a combination of tools that
can be used for such a verification ? If you have a way to verify the
CD writing, please let me know.

I believe this is not the same as "cmp /dev/cdrom iso9660" because of
the table of tokens, etc. Right ? I am not sure what the reading of
the cdrom device will return! Is it documented somewhere ?

thank you

sarantos

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[Gregory Hosler]

Is this a data file cd, or a audio/mixed cd ?

for data only cd's I wrote a verify script, which basically compares the
source files against the new files on the cd. I use "sum" for the comparison,
but you could easily modify the script to use MD5, of crc32, or whatever gives
you warm fuzzies. I don't do raw reads, so audio tracks I am unable to
compare (unless the track is written as a pure data file).

If this sounds useful, reply back, and I'll post the script here (or e-mail
it to you if you are the only respondent). The script is at home, and I am not
so the turnaround will be about half a day.

-Greg

----------------------------------
E-Mail: Gregory Hosler <gregory...@eno.ericsson.se>
Date: 11-Mar-99
Time: 11:44:229

"We've heard that a million monkeys at a million keyboards could produce
the Complete Works of Shakespeare; now, thanks to the Internet, we know
this is not true." Robert Wilensky, University of California

----------------------------------

[David Kelly]

Sarantos Kapidakis writes:
> Recently I found out that I must trust CDs less than what I used to!
>
> How can I verify a CD against the iso9660 I used to write it ? The
> cdrecord has no verify option. Is there a combination of tools that
> can be used for such a verification ? If you have a way to verify the
> CD writing, please let me know.

I use "diff -r --brief /cdrom original-directory". Its not a bad idea
to do this before mastering the image:

% cd original-directory
% find . -type f -exec md5sum > ../manifest.md5
% mv ../manifest.md5 .

Then you or whoever has the CD can type:

% cd /cdrom
% md5sum -c manifest.md5

Any line of output that doesn't include "OK", isn't.

Considering one can dd an image of a single session iso9660 CD to file
then turn around and cdrecord it back, cmp should work, excepting for
the image on CD is 2 blocks longer.

--
David Kelly N4HHE, dke...@nebula.tbe.com
========================================================================
Whom computers would destroy, they must first drive mad.

[Bill Davidsen]

> Recently I found out that I must trust CDs less than what I used to!
>
> How can I verify a CD against the iso9660 I used to write it ? The
> cdrecord has no verify option. Is there a combination of tools that
> can be used for such a verification ? If you have a way to verify the
> CD writing, please let me know.

If you don't mind something slow and UNIX-centric, you can use that same
trick I suggested for checking that a CD was readable.

1. get cksum for the ISO f/s:
mount -r -o loop my.iso /mnt
cd /mnt
find . -type f -print | xargs cksum | sort >master.file

2. get a cksum for the CD
mount -r /dev/cdrom /cdrom
cd /cdrom
find . -type f -print | xargs cksum | sort >cdinfo.file

3. compare:
diff master.file cdinfo.file

If your original data is all in a single based directory, as is often
the case, you can extend this to the original as well. Note that the
sort is needed to get the order to match.

Feel free to substitute crc, md5, or brik as pleases you.
--
-bill davidsen (davi...@prodigy.com)
"The secret to procrastination is to put things off until the
last possible moment - but no longer" -me

[Sarantos Kapidakis]

Thank you all for the many answers.

It seems everybody is using a file comparison approach.
Nobody compares images!
The disadvantage of the file comparison approach is is that it only
verifies files - not other data: e.g. the bootable code on a bootable
CD, other CD extensions like Joliet, hidden files, etc.

To use such a script with a mksiofs image, someone must mount the
image. I would prefer a direct comparison, because I usually make the
iso9660 image on the fly, without storing it, and feed it to cdrecord
from stdin. I plan to recreate the same image for the verify.

I understand that this recreation may give different results for
unitialized image areas, in some circumstances, but this is why a tool
is needed to make the comparison.

Anyway, it seems that a lot of you are interested into comparing
files, and maybe we could converge on a (somehow sophisticated)
script that (does not make the assumption that all files are in one
directory or that they are saved by the same name and) can handle all
mkisofs arguments, and make the comparison. If you know of such a
script, please let me know.

thank you again

sarantos