I'm doing dualboot with Ubuntu and Windows 8 on my DELL Laptop. EFI is enabled, secure boot is not. My partitions are GPT. Everything seems to work for some time. After some normal use, GRUB stops working. The "ubuntu" EFI entry is still there on top of everything else. But the computer boots directly into the Windows Bootloader, skipping GRUB. Any clues on why is that happening or how can I prevent that? My current partiton setup is: - /dev/sda1 NTFS Windows recovery - /dev/sda2 FAT32 UEFI boot (with boot flag) - /dev/sda3 unknown (msftres flag) - /dev/sda4 NTFS Windows Drive C - /dev/sda5 ext4 /home - /dev/sda6 ext4 / I usually reinstall GRUB through chrooting from a Live Session and doing a apt-get install --reinstall grub-efi-amd64.