[CentOS] Installing CentOS 6.2 *TO* a USB drive, not installing from USB.

[Emmanuel Noobadmin]

On 4/5/12, Lamar Owen <lowen at pari.edu> wrote:
> The grub order and names and the linux kernel/udev order and names should
> not be assumed to have any correlation of any kind, since they are
> discovered differently.

Yes, that is what I understand from the grub manual. However, from
that I also understand and expect the first and only device grub could
find would be hd0

> If you can boot a USB live media on this box, you could bring up a grub
> shell and see how grub sees the disks from that (at a root prompt, type
> 'grub' and you'll be greeted with the grub shell, and then you can do
> detection or whatever from that).  This also works in the rescue environment
> given by the install media; you do want to do a 'chroot /mnt/sysimage' in
> that shell before entering the grub shell, though.

I've done this previously from the rescue environment but got no
closer to resolving this.

I've tried it again with a default install of CentOS 6.2, using
default drive layout and all.
On first boot, I get the grub shell but I have not been able to find
any command that would list valid devices grub can find, apart from
the tab button.

Rebooting into the rescue environment, chrooting into the drive,
grub-install generates the map to hd(0) which was expected. Runing
grub shell and trying root (hd0) also works.

However, rebooting after updating the grub device map always results
in "Booting from local disk... Error 21" which indicates grub couldn't
find the drive specified.

Any ideas how I can probe/list devices within grub shell? I've done
the stupid method of root(hd0,x) all the way up to root(hd8,3) without
luck.