Booting an already installed ubuntu from usb external drive

[diegovar]

Hi, I'ts my first post here, a long time Ubuntu user :)

I've installed Ubuntu 9.10 in an internal SATA drive and used it for quite a while, but yesterday my laptop's graphics card decided to die, and it looks like it will be a full month until I get replacement m/b. Therefore, I bought an external USB SATA Hub for my laptop's drive, but I can't seem to be able to boot ubuntu from this drive. I'm trying to boot with this external usb hub attached to an old P4 machine with USB booting enabled.

I get till the grub screen, but as soon as the message "Grub loading" appears, I get a message saying:

error: no such partition

and I get a prompt as follows:
grub-rescue>

I guess grub is trying to boot to a different device name... It's weird, I thought Ubuntu should boot irregardless of which interface I use, be it SATA or USB...


Any help regarding this issue?

Thanks

Diego

[Tylerjd]

Well, I would boot a live cd, go to terminal, and do
sudo grub-update /dev/sdb*sdb could be different depending on the system.

[diegovar]

grub-update doesn-t seem to exist in Grub2.

Running sudo update-grub yields:


grub-probe: error: cannot find a device for /.


if I run sudo grub-install /dev/sdb, I get:


grub-probe: error: cannot find a device for /boot/grub.

No path or device is specified.
Try ``grub-probe --help'' for more information.
Auto-detection of a filesystem module failed.
Please specify the module with the option `--modules' explicitly.


Any ideas?