[nflug] Verifying a cdrom image backup

[Christopher Hawkins]

http://www.mondorescue.org/

See above - it's an open source package that does exactly what you describe. I have used it before and I think there's an option in the menu interface to verify all data on all cds. Maybe you would be better off with their software and maybe not, but either way you might just download their code and see how they do verification.

Agree with Brad... The only way to know is to actually restore it and then compare. Maybe restore then rsync -avn original_dir/* restored_dir/

The -n option means don't transfer anything, just tell what would have been transferred. That will give you a file level comparison that would ignore differences in the underlying media, filesystem, whatever, and you could run it even with the restore on another machine or just with the .iso mounted. 

Chris

----- Original Message -----
From: "Joe" <josephj at main.nc.us>
To: nflug at nflug.org
Sent: Friday, December 12, 2008 2:39:30 AM GMT -05:00 US/Canada Eastern
Subject: [nflug] Verifying a cdrom image backup

I'm making image backups of my system in chunks that fit on cdroms.

I created files such as rootu001.iso, rootu002.iso, etc. using dump with
an unmounted file system.
Then, I used cdrecord to burn a CD which has a file called rootu001 ...
on it.
Next, I ran md5sum against each and they do not match.
I did this twice (two cdroms).
I did an ls -l of both files and the .iso file is somewhat larger than
the one on the cdrom.  There were no error messages, etc. during the
burn (using burnfree which is supported on the drive).  As far as I
know, the cdrom drive is working fine.

I just ran a 15 cdrom backup that worked fine, but I realized afterwards
that since the root file system was mounted, the backup was probably
useless, so I recreated it using a livecd with the root unmounted. 
That's the one I'm having trouble verifying now.

Am I doing something wrong?

How do I verify that what I wrote to the cdrom is identical to the image
on disk and is completely readable - a reliable/restorable copy?

TIA

Joe
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