Ubuntu – Can’t boot into Ubuntu in Windows 10 / Ubuntu dual boot

bootdual-bootgrub2windows 10

I installed Ubuntu on a Dell XPS 13 laptop that had Windows 10 preinstalled on it. I installed it from a USB flash drive on a partition.
When I boot my computer I can only boot into Windows 10 and Ubuntu is nowhere to be seen.

If I boot into my USB then I can see that Ubuntu is installed, but I can't get to it from the BIOS boot menu.

Best Answer

  • Disable the hibernation mode and Fast Boot in Windows.
    Open command prompt as administrator and execute :

    powercfg /h off  
    

    Open the legacy version of the Windows Control Panel (not the modern version).
    Select Energy Settings, enable show hidden settings and uncheck Fast Boot.
    After having done this - shutdown the computer completely - do NOT reboot.
    Boot into the BIOS and select Ubuntu as the default operating system to boot.

    Update :

    In case there is no Ubuntu entry to be found in the BIOS / UEFI settings,
    re-install the GRUB boot loader to your Ubuntu installation in EFI mode.
    Boot from the Ubuntu installation media - open a terminal and execute:

    sudo mount /dev/sdXXX /mnt
    sudo mount /dev/sdXX /mnt/boot/efi
    for i in /dev /dev/pts /proc /sys /run; do sudo mount -B $i /mnt$i; done
    sudo chroot /mnt
    grub-install /dev/sdX
    update-grub  
    

    Note:

    sdX = disk | sdXX = efi partition | sdXXX = system partition

    To identify the partition numbers use GParted - it is included in the Ubuntu installation media.
    Boot into BIOS and select Ubuntu in UEFI settings to be the default operating system to boot.

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