How to get back Windows on the grub menu?

[Bo Berglund]

On Thu, 28 Oct 2021 11:14:07 +0100, Liam Proven <lproven at gmail.com> wrote:

>No. What I was saying is that it *must* be `/boot/efi`. It's a special
>system folder and the bootloader needs to be able to find things there
>and nowhere else.
>

Back again after trying to find my way around this...

I now have the following active mounts on my ubuntu server 20.04.3:

/mnt/ubuntudsk  /dev/nvme0n1p5 (the Ubuntu 20.04.3 desktop
/mnt/windows    /dev/nvme0n1p3 (Windows main disk)
/boot/efi       /dev/nvme0n1p1 (the EFI partition)

Then I tried the following command, which should be able to see the other
operating systems:

sudo os-prober
/dev/nvme0n1p5:Ubuntu 20.04.3 LTS (20.04):Ubuntu:linux

So it *only* sees the Ubuntu Desktop 20.04.3 and not Windows, this is the
problem for fixing the boot menu using this server version of Ubuntu.

So something must still be amiss! But what?

The os-prober command was found in the first anser on this thread:
https://superuser.com/questions/1392316/how-to-add-windows-10-to-grub-boot-loader

BTW:
The active content of the /etc/default/grub file:

GRUB_DEFAULT=0
GRUB_TIMEOUT_STYLE=hidden
GRUB_TIMEOUT=2
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT=""
GRUB_CMDLINE_LINUX="net.ifnames=0 biosdevname=0"

And the efi mount lists this:

ls -l /boot/efi
total 24
drwxr-xr-x 6 root root 4096 1970-01-01 01:00  .
drwxr-xr-x 4 root root 4096 2021-10-28 14:59  ..
drwxr-xr-x 2 root root 4096 2021-01-23 11:38 '$RECYCLE.BIN'
drwxr-xr-x 2 root root 4096 2021-01-23 11:12  BOOT
drwxr-xr-x 5 root root 4096 2021-10-19 19:04  EFI
drwxr-xr-x 2 root root 4096 2021-01-23 10:29 'System Volume Information'

Is there something in here I can modify to get things working?

I believe that since os-prober cannot find Windows it is no meaning to try and
execute update-grub, right?
Since update-grub is changing stuff I do not dare run it because I can damage my
system further...

Maybe the grub menu cannot be fixed from the Ubuntu Server 20.04.3 which was
moved from another PC and then release-upgraded from 18.04?


-- 
Bo Berglund
Developer in Sweden