[NMLUG] Disk-to-disk copying and booting

[Ed at Heron-ent.com (Ed Heron)]

  Please excuse me for jumping in here if I shouldn't.

  I get the impression that not wanting to mount partitions on other than
the first drive is the issue.  If the fstab lists partitions by labels and
the second drive is identical, then the mount program would have ambiguous
information.  If fstab is, in fact, setup this way then changing the labels
to device names should resolve the ambiguity.

  Though I could be missing something...

----- Original Message ----- 
From: "Moses Gold" <moegold2001@yahoo.com>
To: "New Mexico Linux Users Group Mail List" <nmlug@nmlug.org>
Sent: Monday, September 20, 2004 8:55 PM
Subject: Re: [NMLUG] Disk-to-disk copying and booting


>
> is there any reason that partitions on /dev/sdb or /dev/sdc need to be
mounted?
>
>
> --- Ed Brown <ebrown@lanl.gov> wrote:
>
> > The problem may actually be duplicate device "labels", rather than
> > duplicate partitions.  If your /etc/fstab uses "LABEL=" syntax in the
> > first column, try changing those to actual device names, i.e.,
> > /dev/sda1, etc.
> >
> > -Ed
> >
> >
> > On Mon, 2004-09-20 at 09:32, Matthew McCleary wrote:
> > > Hello,
> > >
> > > I am trying to implement a disk-to-disk backup scheme on a server.
> > > It's not the ideal method (I would have chosen a tape backup myself),
> > > but it's what I have to deal with.
> > >
> > > I've got three 146 GB ultra-320 SCSI disks. They are installed in a
> > > removable drive frame, though I do not think they are hot-swappable;
> > > thus, when I install or remove one, I have to first take the machine
> > > down.
> > >
> > > One drive has a complete Red Hat 9.0 system installed on it, which is
> > > essentially one large partition minus a small /boot partition and a 2
> > > GB swap partition. The disk is designated /dev/sda.
> > >
> > > I've been using dd if=/dev/sda of=/dev/sdb bs=1024k (and dd
> > > if=/dev/sda of=/dev/sdc bs=1024k) to make a carbon-copy of sda onto
> > > sdb (or sdc). I'm supposed to do a periodic backup of sda -- something
> > > like once a month, rotating the two backup drives monthly. Thus we
> > > would lose at most a month's worth of work, worst-case.
> > >
> > > Here, I come to the problem. To make a new backup, I just run the "dd"
> > > command again -- it doesn't care what's on the drive currently, and it
> > > will even overwrite the partition map. Quite nice. The problem,
> > > though, happens when next month rolls around and I want to make a new
> > > backup.
> > >
> > > If I take the server down and install one of the backup drives in the
> > > frame, alongside the main drive, and boot it up, Linux freaks. It sees
> > > duplicate /boot partitions (and actually, it would see duplicates of
> > > all filesystems) and refuses to mount anything it sees a duplicate of.
> > > I *think* it actually boots, but it does not mount all filesystems,
> > > which of course will cause problems.
> > >
> > > The only way I can think to get around it is to first delete the
> > > entire partition map on the backup drive (essentially, destroy the
> > > backup) and then install the blank backup disk in the frame, and then
> > > boot. That seems to be the only way I can get Linux to boot normally.
> > >
> > > Problem is, I don't have another server that I can install these
> > > drives into -- and so the only way I can destroy the partition map is
> > > by installing the drives in the very server I'm trying to back up -- a
> > > "chicken and the egg" problem.
> > >
> > > So, I'm appealing to you: what advice would you have for me to go
> > > about solving this problem? A tape backup is (unfortunately) not an
> > > option; due to policy I must do disk-to-disk backups.
> > >
> > > Thanks,
> > > Matthew
> >
> > _______________________________________________
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> > NMLUG@nmlug.org
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> >
>
>
>
>
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