[nflug] Verifying a cdrom image backup

[SilverBear]

Well, I agree it's best to keep data separate, and backed up separately.  But a person might also have his OS tweaked "just so." Reinstalling and then dl/installing  all the right packages could be a hassle.

With prices as low as they are these days, a separate backup HDD that can mirror selected partitions, including OSs, is quite practical. It needn't be always mounted --or even physically connected-- just so long as it's convenient to attach to the system when needed.
Backing up a whole 8GB OS partition with dd from a liveCD usually takes 15-20 minutes or so, if I remember correctly. I have 2GB RAM, so adjust for that. Yes, disk write and bus speeds play a large part in how soon a dd command will complete large amounts of data, but RAM seems to factor in as well.

John

> -----Original Message-----
> From: cloudlakedreamer at yahoo.com
> Sent: Sun, 14 Dec 2008 13:34:41 -0800 (PST)
> To: nflug at nflug.org
> Subject: Re: [nflug] Verifying a cdrom image backup
> 
> Who has time to mess with restoring from lots of CD-ROM's ? I backup my
> data, and then if necessary, I'll just reinstall, then come back and
> restore my scripts, my email, etc... Just an idea, it might save you a
> lot of time.
> 
> Daniel
> 
> 
> --- On Fri, 12/12/08, Christopher Hawkins <chawkins at bplinux.com> wrote:
> 
>> From: Christopher Hawkins <chawkins at bplinux.com>
>> Subject: Re: [nflug] Verifying a cdrom image backup
>> To: nflug at nflug.org
>> Date: Friday, December 12, 2008, 9:37 AM
>> 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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> 
> 
> 
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