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Re: How do I get back the GRUB menu with the blue background?

On Sun 04 Jul 2021 at 10:53:43 (+0200), Stella Ashburne wrote:
> No specific instructions were given to the installer at the "install a boot loader" stage. I just accepted the default. If I remember correctly, the installer of Debian Stretch asked the user to specify the exact location that the boot loader was to be installed. With Debian Buster's installer, there was no need to specify your preferred location.

I find the Grub installation prompts in the d-i very confusing.
I'm wondering whether your process incorrectly updated grub.cfg
in the ESP on the SSD.

Bear in mind there are two grub.cfg files. Here are mine. The
second one is the familiar one, so I just give the head:

# cat /boot/efi/EFI/debian/grub.cfg
search.fs_uuid f3bf6eef-3c26-4070-b180-fd1914377253 root hd0,gpt4 
set prefix=($root)'/boot/grub'
configfile $prefix/grub.cfg

# head /boot/grub/grub.cfg
# It is automatically generated by grub-mkconfig using templates
# from /etc/grub.d and settings from /etc/default/grub

### BEGIN /etc/grub.d/00_header ###
if [ -s $prefix/grubenv ]; then
  set have_grubenv=true

The UUID in the first grub.cfg is correctly pointing to:

$ ls -Glg /dev/disk/by-uuid/f3bf6eef-3c26-4070-b180-fd1914377253
lrwxrwxrwx 1 10 Jul  4 08:00 /dev/disk/by-uuid/f3bf6eef-3c26-4070-b180-fd1914377253 -> ../../sda4

which is an unencrypted¹ buster filesystem that includes /boot.
(I only encrypt /Home and swap.) I'm wondering whether your first
grub.cfg is pointing to the USB stick that you used in the
installation. That would be simple to check. I think I made this
mistake once, which is why I had a set of Grub commands (gleaned off
the web) to boot Windows, as it happened, from a GRUB> prompt, viz:

  GRUB> insmod fat
  GRUB> set root=(hd0,gpt1)
  GRUB> chainloader (${root})/efi/Microsoft/Boot/bootmgfw.efi
  GRUB> boot

If this guess, is correct, it might be possible to confirm it
if you get these symptoms:

. Booting with the internal drive only: GRUB> prompt.
. Booting with the USB stick inserted: something else appears,
  a blue Grub menu, or a Debian installer splash screen,
  or even Windows.

Of course, the second scenario can only work if the USB's UUID
hasn't been recreated by further uses.

¹ With encrypted systems, you have to bear in mind what can be seen
  outside and inside the container. This is easy to distinguish
  with only /home encrypted, as you can inspect things with the
  normal system tools. I don't know what Grub's and initrd's view
  of that world looks like (my initrds don't contain any encryption


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