Ubuntu Installation Stuck at “update-grub”

I have gone through all the similar questions asked about this problem and tried the workarounds mentioned over there but nothing works. Like the ” ps | grep ‘dmsetup create’ ” workaround simply doesn’t work, because I don’t get any output displaying any PID (so I can’t kill any process), then the one regarding deleting 30_os-prober just deletes the file but has no effect on the installation. I am trying to do a clean install on a HDD, can anyone please help me solve this problem. [I am installing Ubuntu LTS 20.04.1 from a live USB]

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Author: Utkarsh Jha

Why can’t grub find the disk by UUID?

I’m trying to troubleshoot why I can’t boot to Windows.

The relevant entry in grub.cfg is:

### BEGIN /etc/grub.d/30_os-prober ###
menuentry 'Windows Boot Manager (on /dev/sda3)' --class windows --class os $menuentry_id_option 'osprober-efi-BC6E-0415' {
        insmod part_gpt
        insmod fat
        set root='hd0,gpt3'
        if [ x$feature_platform_search_hint = xy ]; then
          search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt3 --hint-efi=hd0,gpt3 --hint-baremetal=ahci0,gpt3  BC6E-0415
        else
          search --no-floppy --fs-uuid --set=root BC6E-0415
        fi
        chainloader /efi/Microsoft/Boot/bootmgfw.efi
}

Best I can tell, everything here is correct:
/dev/disk/by-uuid/BC6E-0415 is indeed the Windows boot manager partition.

However I’m slightly confused by the references to (hd0,gpt3) because that’s a completely different partition on a completely different physical disk. hd0 is the disk on which grub is installed though, in case that’s relevant.

The actual error I get when I try and boot Windows is:

error: no such device: BC6E-0415
error: file `/efi/Microsoft/Boot/bootmgfw.efi' not found

I do notice that in grub, if I drop to a grub command prompt and do an ls, the only hard disk I see listed is hd0 when my system actually has 4 hard disks. As I mentioned above, hd0 is the hard disk that has grub and my Linux installs.

So I think my question might be: why, when I boot to grub, can’t grub see any hard disks besides the one grub is on?

If I boot into Linux (Ubuntu 20.04.1) I can see all my hard disks just fine.

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Author: Bridgey

Where does grub-mkconfig get the UUID for root?

When I run grub-mkconfig on Debian 10, it generates smth like:

...
        if [ x$feature_platform_search_hint = xy ]; then
          search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt2 --hint-efi=hd0,gpt2 --hint-baremetal=ahci0,gpt2  fc6c3fbf-8cfc-411c-ac5d-072c6e8c8092
        else
          search --no-floppy --fs-uuid --set=root fc6c3fbf-8cfc-411c-ac5d-072c6e8c8092
        fi
        linux /boot/vmlinuz-4.19.0-9-amd64 root=UUID=e0674dbf-3546-4898-9933-c9eb55703cb5 ro single
        initrd /boot/initrd.img-4.19.0-9-amd64
...

What is being done in this piece of the program and why it uses different UUIDs? And where these UUIDS was taken from?

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Author: Alex Noname