grub does not see the Windows 10 disk/partition
https://askubuntu.com/questions/1564083/grub-does-not-see-the-windows-10-disk-partition
I did see many posts regarding this topic, but none helped me to solve it.
I had an older PC with dual boot Ubuntu and Windows 7 running. both on different disks.
I moved the Ubuntu disk to another PC running Windows 10.
Starting Windows 10 worked as usual, but not Ubuntu, so I used Boot-Repair. On the first run Boot–Repair went through (including removing/installing grub) using the default settings. After restarting there was no grub on any disk (there are 4 internal disks and 2 USB disks with data and for backup). Running disk repair again, trying to define which disk should contain grub and also trying to use the default repair now always gave the following error message:
The current session is in BIOS-compatibility mode.
Please disable BIOS-compatibility/CSM/Legacy mode in your UEFI firmware,
and use this software from a live-CD (or live-USB)
that is compatible with UEFI booting mode.
For example, use a live-USB of Boot-Repair-Disk-64bit
(www.sourceforge.net/p/boot-repair-cd),
after making sure your BIOS is set up to boot USB in EFI mode.
Only BIOS is set to UEFI and I could not find the BIOS-compatibility settings.
Based on some thread in this forum I did the following:
mount /dev/sda5 /mnt
Then run the following to do a chroot to reinstall grub on the system:
for i in /dev /dev/pts /proc /sys /run; do sudo mount -B $i /mnt$i; done
chroot /mnt
The later 2 steps threw an error message, /cow etc. I solved it by sudo apt-get install grub. It seems the Boot–Repair did not install grub properly.
Then you should be at a $ prompt and see your Ubuntu installation. You should now be able to reinstall grub and update grub.
sudo grub-install /dev/sda
sudo update-grub
Only the Windows on disk /dev/sdh was not found
Searching through several threads did not solve it.
What I did:
turned off Fast Boot and Windows power setting: no effect (still left it that way)
trying 40_custom settings using the hd8,1 (for /dev/sdh) did get
grub cannot get C/H/S values
I tried several hdX settings, but none worked.
Next based on another thread:
menuentry "Windows 10" --class windows --class os {
insmod ntfs
search --no-floppy --set=root --fs-uuid 6A4C90714C9039B1
ntldr /bootmgr
}
The uuid is the ntfs partition (/dev/sdh2), I also tried the efi partition uuid (/dev/sdh1)
This had no effect. Windows does not boot from the grub boot menu.
Do you have any other suggestions to get Windows to start from the grub boot menu?
Link to Boot-repair log:
https://paste.ubuntu.com/p/JkrmrzGtWq/
In meantime i did run boot repair twice on the Windows partition
`update-grub2` now finds a Windows 10 installation, but on `/dev/sdd1` which is the efi partition. Windows and the bootmanager is actually installed on `/dev/sdd2`.
using the now available Windows 10 entry does blank the screen a moment and restarts the computer.
/dev/sdd1 entry:
drwxr-xr-x 4 root root 1024 Jan 1 1970 ./
drwxr-xr-x 21 root root 4096 Feb 19 10:52 ../
-rwxr-xr-x 1 root root 1 Dec 7 2019 BOOTNXT*
drwxr-xr-x 41 root root 4096 Feb 21 10:31 Boot/
drwxr-xr-x 5 root root 1024 Feb 23 07:34 EFI/
-r-xr-xr-x 1 root root 420238 Oct 19 04:59 bootmgr*
The grub menu entry for Windows 10 points to /dev/sdd1 but i think it should point to /dev/sdd2 or?
