[nflug] Re: Verifying a cdrom image backup --booting issues

Mon Dec 15 23:48:10 EST 2008

Hi, Joe.
That depends on what the new backup OS partition winds up being called when it's attached to the computer. 
If there is a bootloader *in the root partition* of the backup, then adding this chainload command option to the /etc/lilo.conf file will boot the bootloader in, for example, hdb1:

other=/dev/hdb1
label=backup_OS_hdb1

Having the bootloader installed to the root partition is different from having it installed to the MBR of the whole HDD. Obviously, some kind of bootloader needs to be in the MBR. But having a bootloader also installed in the root partition of every OS installed on the machine is a big safety/timesaver plus.

Complications arise. Unlike GRUB, LILO doesn't work if the partition the working /etc/lilo.conf is written on gets hosed. So you have only one OS, and it runs LILO for the whole computer, when that partition gets screwed, LILO may not work.  If the problem with the main OS is just a kernel panic or something, then the /etc/lilo.conf file would still be intact and LILO itself would still work, and you could choose from alternate menu OSs. 

Personally, I put GRUB or LILO in every root partition for each of the Linux OSs I have installed, then have a GRUB installed in the MBR from one of them that is _not_ my main workhorse [hence less likely to get whacked].  Ditto for my laptop, except I use LILO in the MBR there.  [Obviously, I'm a distro junkie.]

The point is that with a bootloader in the root partition of every OS, _chainloading_ to any OS is less likely to cause a boot malfunction than trying to get the correct boot settings for a vmlinuz or initrd line, working from outside the normal boot menu. Chainloading is cool, and when each OS has it's own bootloader on the root partition, it makes life less complicated. If it's a hassle having to click the extra choice everytime you boot [once for the MBR bootloader, a then once again in the boot menu on the root to which you chained] you can always set the timing default on the root bootloaders to instantaneous, with no wait.

I keep thinking I'll write up a sample "boot tute" for GRUB and LILO illustrating this system, but I'm always busy with something else!  But here is a great Forum thread covering GRUB & LILO boot issues:
http://www.justlinux.com/forum/showthread.php?t=144294

BTW, I'm almost finished [I'm NOT working on it single-handed, of course! But I'm the "html/css polisher", so handle the document after all other revisions are made.] revising the Mepis Linux 8.0 User's Manual. If anyone wants to take some time to check it out, I'd appreciate getting feedback on any errors you spot. Warren Woodford is planning on a final release of Mep8 by the end of the year, so we're trying hard to finish it up and get it to him for inclusion on the LiveCD ISO.
http://sblinux.org/m8-081214/index.html
--I know the link is bad to the TOC page [which will be designed o be viewable in non .css/xhtml standards-compliant browsers, unlike the fly-out menu which relies on a compliant browser, leaving MS-IE users unable to navigate].  It's the last thing I'll write, after I'm sure where everything will be. We've gotten some feedback on Sections 1-8 from Forum readers, but those corrections have not yet been made. I just uploaded Sections 9-10  yesterday.

John

> -----Original Message-----
> From: josephj at main.nc.us
> Sent: Mon, 15 Dec 2008 15:34:43 -0500
> To: nflug at nflug.org
> Subject: Re: [nflug] Verifying a cdrom image backup
> 
> That sounds even simpler than what I'm trying to do now, but how easy i
> it to verify that it worked? I guess I just have to unplug my main drive
> and put the backup one in. That's not too tough, but I don't really want
> to pull my system apart every time.
> 
> I have a removable drive bay I could use that holds my current backup
> drive. What I don't know is how to set the machine up so lilo can boot
> from the backup drive as an option on its menu.
> 
> Joe
> 
> SilverBear wrote:
>> 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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