[SOLVED] SOLVED: grub detecting 2 windows10, only one really works

marozsas · 07-19-2020, 10:14 AM

Hi there.

I had an issue in windows 10 and I had to re-install it. Not a big deal.
After reinstalling it, I boot into a live usb and follow the proper procedure to reinstall grub back to /dev/sda. Everything is fine here too.
Now grub menu properly boots on 'opensuse tumbleweed' (sda4) and on 'Windows 10 (on /dev/sda2)', as expected.

What bothers me is there is now 2 entries for windows 10, and this another one didn't work, really. If selected it brings a windows fix mode or something.
This extra wrong menu entry is related to the boot windows auxiliary partition (/dev/sda1) which is needed to windows to boot, but it shouldn't be in the grub menu.

Before windows re-install, grub used to have only one windows 10 menu entry (/dev/sda2).

How can I rid of this extra menu entry ?
I guess (just a guess) some left over file from previous installation is confusing os_prober somehow. But I have no idea what it is or how to fix.

Code:

kimera:/home/miguel # grub2-mkconfig -o /boot/grub2/grub.cfg 
Generating grub configuration file ...
Found theme: /boot/grub2/themes/openSUSE/theme.txt
Found linux image: /boot/vmlinuz-5.7.7-1-default
Found initrd image: /boot/initrd-5.7.7-1-default
Found linux image: /boot/vmlinuz-5.7.5-1-default
Found initrd image: /boot/initrd-5.7.5-1-default
Found Windows 10 on /dev/sda1
Found Windows 10 on /dev/sda2
done
kimera:/home/miguel #

section of /boot/grub/grub.cfg created above only showing the os_prober_section

Code:

### BEGIN /etc/grub.d/30_os-prober ###
menuentry 'Windows 10 (on /dev/sda1)' --class windows --class os $menuentry_id_option 'osprober-chain-CEFE7B31FE7B1147' {
        savedefault
        insmod part_msdos
        insmod ntfs
        set root='hd0,msdos1'
        if [ x$feature_platform_search_hint = xy ]; then
          search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 --hint='hd0,msdos1'  CEFE7B31FE7B1147
        else
          search --no-floppy --fs-uuid --set=root CEFE7B31FE7B1147
        fi
        parttool ${root} hidden-
        drivemap -s (hd0) ${root}
        chainloader +1
}
menuentry 'Windows 10 (on /dev/sda2)' --class windows --class os $menuentry_id_option 'osprober-chain-0A1CA2CC1CA2B1DD' {
        savedefault
        insmod part_msdos
        insmod ntfs
        set root='hd0,msdos2'
        if [ x$feature_platform_search_hint = xy ]; then
          search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos2 --hint-efi=hd0,msdos2 --hint-baremetal=ahci0,msdos2 --hint='hd0,msdos2'  0A1CA2CC1CA2B1DD
        else
          search --no-floppy --fs-uuid --set=root 0A1CA2CC1CA2B1DD
        fi
        parttool ${root} hidden-
        drivemap -s (hd0) ${root}
        chainloader +1
}
### END /etc/grub.d/30_os-prober ###

PS: I've added

Code:

GRUB_OS_PROBER_SKIP_LIST="CEFE7B31FE7B1147@/dev/sda1"

to /etc/default/grub and it works. grub2-mkconfig now ignores /dev/sda1.

yancek · 07-19-2020, 12:06 PM

What is the partition in question? sda1. Is that or was that a boot partition for an earlier version of windows? Can you mount it and take a look at the folders/files there and possibly post that info here? Fix mode or something is a bit vague, you might reboot again and get the actual error as there are a number of members here very familiar with windows who might be able to help.

marozsas · 07-19-2020, 12:40 PM

Quote:

Originally Posted by yancek

What is the partition in question? sda1.

Yes, sda1 is the extra menu entry.

Quote:

Originally Posted by yancek

Is that or was that a boot partition for an earlier version of windows?

Yes. It is. This partition always be there. It was created by windows installer back in the original install in a empty disk. I didn't touch on it.

Quote:

Originally Posted by yancek

Can you mount it and take a look at the folders/files there and possibly post that info here?

Sure. Here it is:

Code:

kimera:/home/miguel # mount -o ro /dev/sda1 /mnt/sda1
kimera:/home/miguel # ls /mnt/sda1
$RECYCLE.BIN  BOOTNXT  BOOTSECT.BAK  Boot  Recovery  Recovery.txt  System Volume Information  bootmgr
kimera:/home/miguel # umount /dev/sda1

Quote:

Originally Posted by yancek

Fix mode or something is a bit vague, you might reboot again and get the actual error as there are a number of members here very familiar with windows who might be able to help.

Because it is not important. The presence of /dev/sda1 is normal. Nothing wrong with that.
What is wrong is grub creating a entry for it that does not works, nor intended to work at all.
The correct windows boot partition is /dev/sda2.

Editing the file /boot/grub2/grub.cfg and removing the /dev/sda1 entry it is fine, but I have to do that every time a new kernel is installed.

marozsas · 07-20-2020, 07:40 AM

I think I understand now what happened.
The presence of folder /Boot in a ntfs partition triggers the detection of a bootable windows partition by the script /etc/grub.d/30_os-prober.
Usually you have /Boot only on the auxiliary partition (mine was /dev/sda1, the one that I've listed the content in a previous post in this thread).
This was my initial situation. /boot on /dev/sda1 only.

When I had to reinstall windows it did differently on the second time. The windows installer created another /boot folder on /dev/sda2 and completely ignored the /dev/sda1 partition that it have created before.
As result my system ended with 2 /boot folders, one of then (the one on /dev/sda1) useless to boot the new install, as the new install relies entirely on /dev/sda2.

To avoid the detection of /dev/sda1 as a windows system in grub, I've renamed the /Boot on /dev/sda1 to /old.Boot. Now grub does not add /dev/sda1 to the grub boot list.
Of course the Windows is booting fine, since it is not depends on files on /dev/sda1 to boot.