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Re: rescue grub -- help!



Lennart Sorensen wrote:
On Thu, Mar 23, 2006 at 08:01:16PM -0800, David Liontooth wrote:
I cloned a drive, starting with the MBR:

 dd if=/dev/hda of=/dev/hdc  bs=446 count=1

However, after installing the cloned drive in the new machine, all I get
is a scrolling GRUB filling the screen. I downloaded an amd64 netboot
CD, mounted / and /boot in /target, and issued

   chroot /target

Everything in there works fine -- the applications run. (I'm sitting at
another computer at this point with remote access to the installer). But
what I was counting on working, namely

   grub-install  /dev/hda

How about grub-install '(hd0)' ?  Does that work?

When cloning a disk, you have to remember the MBR contains block maps of
where on the rest of the disk to read stage2 for grub.  After that it
can read filesystems and doesn't care if files move.  So doing a
grub-install on a drive after messing with the partitions is a good
idea.

Len Sorensen


Hi Len,

No, it'd didn't -- when I booted with the installation CD, chroot didn't see the drives at all, even though chroot was running on the drive I was trying to do a grub-install on. This is different from my experience with boot floppies and I thought it was perhaps a change in policy. I still don't understand why this failed -- I ended up installing a new partition. This is amazingly user-unfriendly, so I'm trying to understand what happened. Surely I can use an installation CD as a rescue disk still?

SuSE -- in the old days, before I found religion -- had a feature in their installation disk that looked at an existing installation and sanitized it. In this case, all I wanted was to do a grub-install and I couldn't do it.

So this is not policy? It should have worked? The command you suggest is what I tried, along with several variants. It simply did not see the drives. Nor could I get to the MBR outside of the chroot, as the installer insists on setting up its own base-install before it lets you run grub. Maybe I should ask, what is the command in the install-disk that eventually runs grub?

I'm just amazed how continually frustrating it is to install Debian -- the experience compares with nothing else. A fresh install is obviously way ahead of where it used to be, but a simple rescue on machines that don't have floppy drives is still an arcane science.

Dave








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