[SOLVED} Windows 10 dual boot

Roken · 2021-05-20 17:11:57

This has been driving me nuts for a week.

I rarely boot Windows, and for convenience, I have disabled os-prober in grub.cfg, having previously let os-prober find Windows 10 and then adding an entry to /etc/grub.d/40_custom. I also have an entry in there for my portable Arch drive. This worked no problems for a long while. I could boot Windows via grub, update it, then reboot back to Arch.

Recently, selecting Windows from GRUB gives me an "Invalid signature" error, and here is where my journey started. I figured just let os-prober loose, create a windows entry in /etc/grub.d/40_custom and regenerate grub.cfg. No go. os-prober can no longer find Windows.

My setup is, Arch is on my NvME drive.
Windows has it's own SSD.
I also have 3 other SSDs.

The SSDs are not connected to the MB SATA ports, but are connected to an add in SATA PCI card (I have two GPUs and they foul the MB SATA ports with both installed).

If I change the boot order in BIOS, I can boot Windows directly with no issue. I've tried Windows boot repair. The GRUB menu entry exists (but fails as mentioned). I even tried copying the contents of the Windows EFI folder to my /boot/EFI directory.

Still no joy getting the grub entry to work.

For info:

fdisk -l

as far as is relevant:

Disk /dev/sdb: 931.51 GiB, 1000204886016 bytes, 1953525168 sectors
Disk model: Samsung SSD 860 
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 49F98043-0099-11EB-85CF-244BFE4AD6BD

Device          Start        End    Sectors   Size Type
/dev/sdb1        2048    1126399    1124352   549M Microsoft basic data
/dev/sdb2     1126400 1952247117 1951120718 930.4G Microsoft basic data
/dev/sdb3  1952247808 1952452607     204800   100M EFI System
/dev/sdb4  1952452608 1953519615    1067008   521M Windows recovery environment

blkid

again, as far as is relevant:

/dev/sdb4: BLOCK_SIZE="512" UUID="90665D3F665D276E" TYPE="ntfs" PARTUUID="49f98042-0099-11eb-85cf-244bfe4ad6bd"
/dev/sdb2: BLOCK_SIZE="512" UUID="92121C2F121C1B35" TYPE="ntfs" PARTUUID="49f98040-0099-11eb-85cf-244bfe4ad6bd"
/dev/sdb3: UUID="10B8-0371" BLOCK_SIZE="512" TYPE="vfat" PARTUUID="49f98041-0099-11eb-85cf-244bfe4ad6bd"

And the current grub.cfg entry

menuentry 'Windows' --class windows --class os $menuentry_id_option 'osprober-efi-52D5-DA3F' {
	savedefault
	insmod part_gpt
	insmod fat
	insmod ntfs
	set root='hd2,gpt3'
	search --no-floppy --fs-uuid --set=root 52D5-DA3F 
	chainloader /efi/Microsoft/Boot/bootmgfw.efi
}

I'm not seeing anything wrong with any, so why does boot fail and why does nos-prober not see what is a working Windows drive. EDIT: For info. I tried changing the root UUID in the GRUB entry to 10B8-0371, and I still get the "Invalid signature" error. I also changed the Windows boot to

chainloader /EFI/Microsoft/Boot/bootmgfw.efi

with no change. For fun, I prepended "/boot" but that then reports that bootmgfw.efi is not found.

I have tried mounting the Windows partitions before trying os-prober, and it still draws a blank. (NB - I've been testing using os-prober alone since it was clear it was making no difference via grub-mkconfig). This was working until a couple of weeks ago with no problems.

Additional, possibly relevant info. GRUB has it's own 512Mb partition on the NvME drive, and is always mounted at boot time. Arch upgrades of kernel etc. perform as expected, and so there is no issue with my Arch EFI mount. I feel that os-prober will fix my issues, but I'm out of ideas, and Google isn't helping, giving links to solutions that I've already tried.

My final option will be to take the damned thing apart and plug the Windows drive into a SATA port on the MB, but this should not be necessary.

Last edited by Roken (2021-05-25 14:03:43)

Roken · 2021-05-25 14:04:19

Dunno how, but suddenly GRUB was starting in MBR rather than UEFI mode. Fixed that and all is working again.

Arch Linux

#1 2021-05-20 17:11:57

[SOLVED} Windows 10 dual boot

#2 2021-05-25 14:04:19

Re: [SOLVED} Windows 10 dual boot

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