Grub does not see Windows MBR

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1

After Manjaro 21.0.7, it appears that Grub did not detect Windows 10 boot. I browsed the forum. Most of the time it’s about Manjaro having UEFI boot whereas Windows has BIOS boot.

I am not sure this is my case. Here are the outputs of the command that are often required in the forum to tackle this issue.

$ sudo parted -l
[sudo] Mot de passe de xxx : 
Modèle : ATA Samsung SSD 840 (scsi)
Disque /dev/sda : 500GB
Taille des secteurs (logiques/physiques) : 512B/512B
Table de partitions : gpt
Drapeaux de disque : 

Numéro  Début   Fin    Taille  Système de fichiers  Nom                   Drapeaux
 1      1049kB  500GB  500GB   ntfs                 Basic data partition  msftdata
 2      500GB   500GB  555MB   ntfs                                       caché, diag


Modèle : ATA SAMSUNG HD153WI (scsi)
Disque /dev/sdb : 1500GB
Taille des secteurs (logiques/physiques) : 512B/512B
Table de partitions : msdos
Drapeaux de disque : 

Numéro  Début   Fin     Taille  Type     Système de fichiers  Drapeaux
 1      1049kB  1500GB  1500GB  primary  ntfs


Modèle : ATA Samsung SSD 750 (scsi)
Disque /dev/sdc : 250GB
Taille des secteurs (logiques/physiques) : 512B/512B
Table de partitions : gpt
Drapeaux de disque : 

Numéro  Début   Fin    Taille  Système de fichiers  Nom  Drapeaux
 1      1049kB  538MB  537MB                             legacy_boot, msftdata
 3      538MB   852MB  315MB   fat32                     msftdata
 2      852MB   250GB  249GB   ext4

sda is a SSD that contains my Windows 10. sdb is my 2TB hdd for data. sdc1 contains the Windows boot, sdc2 contains Manjaro.

Then :

$ test -d /sys/firmware/efi && echo efi || echo bios
efi

$ efibootmgr -v
BootCurrent: 0000
Timeout: 1 seconds
BootOrder: 0009,0000,0006,0001
Boot0000* Manjaro       HD(3,GPT,039e796b-ef56-1b44-acc2-0ffee941b9fe,0x100800,0x96000)/File(\EFI\Manjaro\grubx64.efi)
Boot0001* Hard Drive    BBS(HD,,0x0)..GO..NO........o.S.a.m.s.u.n.g. .S.S.D. .8.4.0. .E.V.O. .5.0.0.G.B....................A...........................>..Gd-.;.A..MQ..L.1.S.H.D.S.N.D.A.3.B.2.0.1.2. .H. . . . ........BO..NO........o.S.a.
m.s.u.n.g. .S.S.D. .7.5.0. .E.V.O. .2.5.0.G.B....................A...........................>..Gd-.;.A..MQ..L.3.S.S.3.W.N.H.C.6.7.4.1.5.4. .D. . . . ........BO..NO........o.S.A.M.S.U.N.G. .H.D.1.5.3.W.I....................A............
...............>..Gd-.;.A..MQ..L.1.S.V.U.1.J.Z.C.0.8.5.0.5.9. . . . . . ........BO
Boot0006* UEFI OS       HD(3,GPT,039e796b-ef56-1b44-acc2-0ffee941b9fe,0x100800,0x96000)/File(\EFI\BOOT\BOOTX64.EFI)
Boot0009* Windows Boot Manager  HD(2,GPT,1fbea5c9-6d81-45f9-8e33-b7a6eb26af3f,0x3a27d000,0x108800)/File(\EFI\Microsoft\Boot\bootmgfw.efi)

Finally, os-prober does not return anything

$ sudo os-prober
$

I don’t understand why os-prober does not see the Windows boot in sdc1. How can I add an entry to grub menu so that I can boot on Windows ?

By the way, if I select the Windows MBR at BIOS time instead of Manjaro, I can successfully boot on Windows.

Thank you in advance for your help

2

Hello @nico :wink:

The topic has been covered ad nauseum now so I wonder why you can’t find it, but just briefly explained here:

You installed Windows in UEFI mode last, no idea when. But it is installed without an EFI Partition now:

But Manjaro has a EFI Partition (FAT32 one):

If Grub, therefore Manjaro, is installed in UEFI mode then it will not find an OS installed in BIOS mode. Both have to be installed in the SAME MODE.

Best regards :wink:

3

there is something wrong here
on sdc , if boot Efi microsoft was here ,
you will have Boot & Esp flag on

when did you create sdc3 , before install manjaro , or after install manjaro ?

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