If you have some problematic computer like HP Pavilion 17, Windows or windows-based malwares can destroy boot. If so, you need to install and configure via liveUSB, because boot-repair, etc. may not work with HP. The process: 1. Boot using liveUSB, open Terminal and mount efi-partition under /mnt and open /mnt as an administrator and copy /mnt/EFI/Microsoft/Boot to /mnt/EFI/Microsoft/Boot2 and rename /mnt/EFI/Microsoft/Boot/bootmgfw.efi and /mnt/EFI/Microsoft/Boot/bootmgr.efi files. 2. Copy /mnt/EFI/ubuntu/grubx64.efi (copy twice) and /mnt/EFI/ubuntu/grub.cfg files to the /mnt/EFI/Microsoft/Boot folder and rename grubx64.efi as bootmgr.efi and bootmgfw.efi. 3. Umount /mnt 4. Chroot to your linux-system (eg. /dev/sda7) sudo mount /dev/sda7 /mnt sudo mount --bind /dev /mnt/dev sudo mount --bind /sys /mnt/sys sudo mount --bind /proc /mnt/proc sudo chroot /mnt nano /etc/resolv.conf ... the contents nameserver 8.8.8.8 .... save and quit Ctrl o Ctrl x apt-get update apt-get install grub-efi-amd64 mount /dev/sda2 /boot/efi ### if the efi partition is /dev/sda2 apt-get install --reinstall grub-efi update-grub exit sudo umount /mnt/dev sudo umount /mnt/sys sudo umount /mnt/proc sudo umount /mnt Now you should be able to boot into your linux-system. For getting Windows to boot also, you need to make an /etc/grub.d/40_custom file, whose contents is #! /bin/sh exec tail -n +3 $0 menuentry "Windows" { insmod part_gpt insmod chain set root='(hd0,gpt2)' chainloader /EFI/Microsoft/Boot2/bootmgfw.efi } Notice that the path is /EFI/Microsoft/Boot2 ! After making run sudo update-grub