Score:1

How can i install grub loader manually in ubuntu 21.10?

cn flag

I recently installed ubuntu 21.10 dualboot with windows 10. Grub install failed during the installation and the system boots into Linux automatically. If i boot into the Windows partition with the boot menu it goes to grub rescue. I tried running sudo update-grub and changed GRUB_TIMEOT_STYLE from hidden to menu but nothing happens. Here is a picture of the disk with Ubuntu:

enter image description here

And here is a picture of the disk with Windows: enter image description here

oldfred avatar
cn flag
Is this an old system? What brand/model & what video card/chip? You are showing MBR(msdos) partitions as you have an extended partition. Windows only installs in the now very old BIOS boot mode to MBR drives and only in UEFI mode to gpt partitioned drives. Since two drives and old BIOS install, you want the Windows boot loader in sdc and grub2's boot loader in sda. Grub only boots working Windows and if a Windows update turns fast start up back on then you have to directly boot Windows or use Windows repair recovery flash drive to fix Windows. If Ubuntu install UEFI? Installs must be same.
Score:1
us flag

Boot Repair will not repair Windows boot files. When Windows is installed it should make its own EFI folder of boot files, and it is normally about 100 MB in size, which is big enough to include the grub efi files also. Did you install Windows after Ubuntu?

As you have a grub EFI of 4.2GB it is not only a waste of space, but suggests that the Windows EFI has somehow been wiped, and sda6 serves for Linux booting only. So Windows boot files may be missing from sda6, thus Windows won't boot. If you run sudo ls /boot/efi/EFI, is Microsoft shown as a folder? If so, what does sudo ls /boot/efi/EFI/Microsoft/Boot|grep -i ^b show?

Score:1
in flag

This is not exactly an answer, because this would not be "manually", but I achieved good results with "Boot Repair". See: https://help.ubuntu.com/community/Boot-Repair

nineninesevenfour avatar
in flag
But Paul Benson is right, and "Boot Repair" was just a first guess to improve the overall situation. It would be great if you could provide the output of `sudo find /boot/efi`, `sudo cat /boot/efi/EFI/BOOT/grub.cfg` and `cat /etc/default/grub` to give you a more profound answer. The partition scheme alone just leaves us guessing and we do not know, if the Windows boot entries are still intact.
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