Hello,
I have a Lenovo T400 laptop which uses a legacy BIOS which can not boot
from an UEFI partition. I want to install Ubuntu on a 3TB external USB
disk to make it a rescue disk to store images from the laptop builtin
disk on it.
The external USB disk has 4k sectors instead of the usual 512k ones
because it is a 3TiB-Disk which exceeds the 2TiB-Limit addressable with
512k-sectors.
Originally the disk had a traditional "msdos" partition table, hower
with 4k sectors. I could not boot Ubuntu from it.
Then I learned that one can install Ubuntu on a GPT formatted disk, if a
dedicated boot sector of appropriate size is provided. I changed the
partition scheme of the disk to GPT, I installed Ubuntu and configured
GRUB2 on this disk accordingly (no error messages during ths process).
However, I could not boot from the external disk.
I started a thread in the German ubuntu wiki
https://forum.ubuntuusers.de/topic/kein-booten-von-einer-externen-3tb-festplatte-/,
it extends through three pages to
https://forum.ubuntuusers.de/topic/kein-booten-von-einer-externen-3tb-festplatte-/3/.
One idea from this discussion is, to configure GRUB2 on the builtin
drive such that it would also offer to boot from the external USB disk.
However it looks like Grub does not recognize the USB disk in the phase
of the GRUB menu. I entered *ls* there which returns:
*(hd0) (hd0,msdos5) (hd0,msdos1)*
* Do you have any idea, how to overcome this situation?
* Is GRUB2 started from the traditional 512k-sector builtin diskable
to detect an installed Ubuntu on the external USB drive once it has
come up to the moment, when the GRUB menu becomes accessible?
* Will it be able to boot Ubuntu installed on the external disk
(directly, not using the GRUB2 installed there whicht might not work
because my BIOS is not "GPT aware")?
This problem seems to become more and more severe since at my last visit
of a computer shop, all external storage disks in the TiB range were
4k-sector ones. The vendor told me that one can distinguish them from
512k-onnes, if they do NOT mention to be Windos XP compatible. This is
the criterion to distinguish Advanced partition disks from the others,
they told.
Kind regards
Adalbert Hanßen
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