How to replace a hard drive...

[Andrew Cowie]

On Thu, 2011-05-12 at 12:39 -0400, Peter King wrote:

> the new disk, and installed grub manually. All seemed to go well. Reboot, and the new disk
> is seen by the BIOS; it finds grub on the MBR and loads it; I select a kernel and start to
> boot up -- by this time I'm starting to think it will work -- and then, after it correctly
> finds my keyboard, it just, well, stops. Nothing. No drive activity, no indication of life.

We hit something like this last week for a client. We had to replace the
boot disks in a storage machine, and the UUID × grub2 interaction bit us
rather badly.

Trying to get to single user mode never worked; it would still hang. It
seems that Ubuntu have added so many things such that if a normal (!
noauto) mount in /etc/fstab fails, then it just hangs. I would have
expected the "Enter system password or Ctrl+D to continue" but no, just
stuck.

The way we got around it was to manually delete all the setup and
root=UUID= references from the grub boot line and spec'd root= manually.
Eventually I hit on a combination that dropped not to "Enter system
password" but "(initramfs)"

I never found the root cause, but our guess was that the grub map (I
thought that went away with grub2) still had wrong UUIDs in it even
though we removed them from the boot lines.

Anyway, Canonical's (initramfs) is crippled - there's no editor there! -
but you can mount and copy. So the workaround was to grab
broken /etc/fstab, copy it off to a separate USB stick, take it to
another machine, mount & edit it there. Then you can take it back and
copy the fixed file over the broken one. Then we got booted to single
user, were able to reinstall grub, and then finally were on our way.

That's probably all particular just to the fstab based problem we were
having, but the general copy-out-copy_back approach might help for a
number of related problems.

Good luck,

AfC
Sydney

-- 
Andrew Frederick Cowie

Operational Dynamics is an operations and engineering consultancy
focusing on IT strategy, organizational architecture, systems
review, and effective procedures for change management: enabling
successful deployment of mission critical information technology in
enterprises, worldwide.

http://www.operationaldynamics.com/

Sydney   New York   Toronto   London
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