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How do I manually add OS to grub?
Manually editing the GRUB files
- Open the /etc/grub. d/40_custom file as root with a text editor. sudo nano /etc/grub.d/40_custom.
- Add the menuentry.
- Save the file.
- Update the GRUB 2 menu (the file /boot/grub/grub.cfg) with update-grub. sudo update-grub.
How do you install Windows without losing grubs?
Physically disconnect all drives except my new one (and the bootable USB with Windows on it) from the motherboard. Boot with the USB and install Windows on the remaining drive. Boot into the new Windows drive normally and finish the setup sequence (which requires multiple reboots)
How do I install GRUB?
Installing GRUB2 on a BIOS system
- Create a configuration file for GRUB2. # grub2-mkconfig -o /boot/grub2/grub.cfg.
- List block devices available on the system. $ lsblk.
- Identify the primary hard disk.
- Install GRUB2 in the MBR of the primary hard disk.
- Reboot your computer to boot with the newly installed bootloader.
Why is grub not showing on Windows 10 upgrade?
During installation process, after the first reboot, i get the grub rescue prompt, fixed this with BootRepair in a USB stick. Grub now appears, but is only showing Ubuntu partition, not Windows. Now Windows shows back up in grub menu, continue with Windows 10 upgrade.
How to fix grub and boot-repair in Windows 10?
If you have a Win10 installation media you may use this to install a new fresh MBR. Just boot intil you see “Install now” (or similar) but do not click on it. There is a small link saying “repair tools” (or something). From this you may enter command prompt. This should fix the issue.
How can I update Grub from my Ubuntu partition?
Update: I’ve attempted to use chroot to update grub from my Ubuntu partition. update-grub runs successfully finding both linux and windows boot manager but the process still doesn’t have any effect. grub-install complains that it cannot find EFI directory (but I have mounted everything correctly).
If the Microsoft boot loader is at number 2, move it to the bottom and reboot. You can check it from within Ubuntu by running sudo efibootmgr -v in terminal. We have a number of answers here providing steps on how they fixed the issue (Loss of Grub menu due to latest Win10 update).