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Fw: Fw: Grub cannot see my new hard drive

The computer's startup/settings menu does not detect the 4 TB drive so it does not list it as a bootable device. I cannot boot from the 4 TB drive. It gives me an error saying that it cannot find the file system UUID (whatever code for /dev/sdb1) when grub starts from /dev/sda. It then gets confused and supports nothing. fdisk does not offer an option to make /dev/sdb1 bootable/active. I used 17 different partitions on /dev/sdb, the first of which starts 1 MiB in.

name=Matthew%20Campbell&email=trenix25%40pm.me





-------- Original Message --------
On Jul 2, 2020, 1:08 PM, David Wright < deblis@lionunicorn.co.uk> wrote:

On Thu 02 Jul 2020 at 08:12:00 (+0000), Matthew Campbell wrote:
> On Jul 1, 2020, 7:50 PM, David Wright wrote:
> > On Wed 17 Jun 2020 at 05:14:22 (+0000), Matthew Campbell wrote:
> >> […]
> >> I booted from a USB 2.0 flash drive into Grub2.
> >> […]
> >> /dev/sdb is the new 4 TB Toshiba External USB 3.0 hard drive.
> >> […]
> >> The hard drive, /dev/sdb, always responds faster than the USB flash drives so it is always /dev/sdb.
> >>
> >> Now Debian Linux is running on my new hard drive using /dev/sdb1 as the root partition.
[…]
> The 4 TB hard drive uses a GPT type partition table, not an MBR type table, which is why the computer can't see it. It can't make sense of GPT tables.

If your computer can't make sense of GPT tables, how are you able to
run Debian Linux from its first partition?

I think what you might be trying to say is that you haven't managed to
boot from a GPT disk connected by USB. But if you can boot with Grub
from an MBR stick, that suggests that something is missing on your
GPT disk.

Have you tried to install Grub on your 4TB disk? What did it say?
Were there any error messages.

How is this disk partitioned? Did you do it, or is it just as it
was bought? I'll give you an example of how I have system disks
partitioned. You don't necessarily have to follow it, but it might
help you to deal with yours.

--✄--------

# fdisk /dev/sda

Welcome to fdisk (util-linux 2.33.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Command (m for help): p
Disk /dev/sda: 465.8 GiB, 500107862016 bytes, 976773168 sectors
Disk model: ST3500641A
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: A519207D-4D17-4727-A35D-55B72A0CB95B

Device Start End Sectors Size Type
/dev/sda1 2048 8191 6144 3M BIOS boot
/dev/sda2 8192 1023999 1015808 496M EFI System
/dev/sda3 1024000 2047999 1024000 500M Linux swap
/dev/sda4 2048000 63487999 61440000 29.3G Linux filesystem
/dev/sda5 63488000 124927999 61440000 29.3G Linux filesystem
/dev/sda6 124928000 976773119 851845120 406.2G Linux filesystem

Command (m for help): M
Entering protective/hybrid MBR disklabel.

Command (m for help): p
Disk /dev/sda: 465.8 GiB, 500107862016 bytes, 976773168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x00000000

Device Boot Start End Sectors Size Id Type
/dev/sda1 1 976773167 976773167 465.8G ee GPT

Command (m for help): q

#

--✄--------

This drive is inside a 2000-built PC. (It can't boot from any sort of
USB device.) The second partition table shows the protective MBR,
which contains the Grub code for the PC to boot from.

The first partition table is the GPT one. Partitions 4 and 5 are
for root filesystems, one for stretch and one for buster. When
bullseye is released, I'll most likely overwrite the stretch one.
Partition 3 is for swap, and 6 is for /home. Both these are encrypted
in different ways.

That leaves the more interesting ones. Partition 2 is to enable the
drive to be used to boot an EFI system, and is obviously unused by
this PC. (I could "borrow" it for more swap, but the PC only has
500MB memory, so probably pointless for the tasks it does.)

Partition 1 is where Grub puts the Second Stage code that it requires
to read the disk partition table and filesystems, so that it can find
grub.cfg, the kernel and initrd. On a "real" MBR disk, there is
typically plenty of room between the partition table and the first
partition for this code, but on a GPT disk, that space is where
the partition table itself resides; so Grub has to find somewhere
else. That's what partition 1 is for.

My *guess* is that your Grub is booting ok, but has no (or little)
Second Stage code to determine anything about the drives beyond
their existence, so you just get the Grub prompt.

Note that it's not important where Grub puts its code, only that
there is some space somewhere. On this laptop, my BIOS Boot
partition is sda9, because BIOS booting was late to the party
on what was bought as a Windows/EFI/GPT machine.

Cheers,
David.

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