Ubuntu – Dual-boot boot menu does not show up after installing Ubuntu 15.10 alongside Windows 10

15.10dual-bootgrub2windows 10

I have installed Ubuntu 15.10 alongside Windows 10 with UEFI. To install Ubuntu, I chose the option install alongside Windows 10 or something similar to this. Then I created a new partition for Ubuntu and installed it. After installation, the boot menu did not show up. Initially I thought Ubuntu has not been installed, but when I plugged in the USB drive and wanted to install Ubuntu I saw an option of reinstalling Ubuntu on my machine. So, I found out that Ubuntu is installed. Pressing F8 and F12 also does not help.

Can anyone help me bring up the GRUB boot menu?

In Windows, I also entered the command bcdedit /set {bootmgr} path \EFI\ubuntu\grubx64.efi in cmd, but still the boot menu does not show up.

Reply (Himanshu) :
Just boot in bios and, if you can, add boot option with name say ubuntu and path EFI/ubuntu/shimx64.efi. No need for live PCB or anything. Move the boot option to top. This is for dell GUI bios but I assume it works for all. Or you may want to see this or this, where you can enable Windows Boot Loader for one boot or forever as you wish, and boot Ubuntu from it. If you want now, you can use the installed Ubuntu terminal to use the commands update-grub to use GRUB instead. (Not enough reputation to answer properly btw.)

Best Answer

    1. On Windows 10, go to the start menu.

    2. Search and open Recovery Options. The description for it should say System settings.

    3. Under Advanced startup click Restart now.

    4. Click Use a device; it's description should say "Use a USB drive, network connection, or Windows recovery DVD".

    5. Click Ubuntu and hopefully it should take you to the grub boot menu.

    6. Next try going back to the live Ubuntu session on the USB to reinstall grub-efi. On the live session, open a terminal and enter the following commands in:

      sudo mount /dev/sda# /mnt
      

      Replace the hashtag in /dev/sda# with the number representing the partition where you had Ubuntu installed. You can check using gnome-disks or gparted.

      sudo mount /dev/sda# /mnt/boot/efi
      

      Replace the hashtag in /dev/sda# with the number representing the EFI partition. It's usually /dev/sda2.

      sudo mount -o bind /dev /mnt/dev
      sudo mount -o bind /proc /mnt/proc
      sudo mount -o bind /sys /mnt/sys
      sudo mount -o bind /run /mnt/run
      sudo chroot /mnt/
      sudo apt-get install --reinstall grub-efi
      sudo update-grub
      

      Reboot.

    7. If that fails, go to your BIOS settings with one of the F keys; that option might be Enter setup. Look for boot option priorities and move Ubuntu above the Windows Boot Manager. Go to the option to save the changes then reboot.

    8. Lastly you can try using Boot-Repair.