Probe Current sda Disk and Install GRUB. Debian 12. Part.2.

GRUB Configuration Guide

My current situation is this:

[
root@debian:/home/user001# sudo os-prober
/dev/sda1@/EFI/Microsoft/Boot/bootmgfw.efi:Windows Boot Manager:Windows:efi
/dev/sda6:Debian GNU/Linux 12 (bookworm):Debian:linux
/dev/sda7:Debian GNU/Linux 12 (bookworm):Debian:linux
]

/dev/sda7 is the current / ;

I am using it just now;

Setup grub accordingly.

Given that /dev/sda7 is currently my root (/) partition, you can set up GRUB to use /dev/sda7 as the default boot option. Here’s how to configure GRUB to ensure it prioritizes /dev/sda7 and includes entries for both /dev/sda6 and /dev/sda1 as detected by os-prober.

Step 1: Set /dev/sda7 as the Default Entry in GRUB

Edit /etc/default/grub:

Open the GRUB configuration file:

sudo nano /etc/default/grub

Set GRUB_DEFAULT to the Debian entry on /dev/sda7:

Since both /dev/sda6 and /dev/sda7 contain Debian, specify /dev/sda7 as the default entry by using the name detected by os-prober.

Find the line that begins with GRUB_DEFAULT= and set it as follows:

GRUB_DEFAULT="Debian GNU/Linux 12 (bookworm) (on /dev/sda7)"

If specifying the entry by name doesn’t work, you can try setting it by index. To find the index, you could restart to see where sda7 is in the GRUB menu.

Save and Close the File.

Step 2: Update GRUB

Run the following command to update the GRUB configuration with the new settings:

sudo update-grub

Step 3: Reinstall GRUB on /dev/sda

Reinstalling GRUB on /dev/sda ensures that it loads correctly with the updated configuration:

sudo grub-install /dev/sda

Step 4: Reboot to Test

Reboot the system to confirm that GRUB now prioritizes /dev/sda7 as the default boot entry:

sudo reboot

After rebooting, GRUB should default to booting from the OS on /dev/sda7.