On 02/01/2018 12:15 PM, wwp wrote: > Hello there, > > > Dell XPS-15-9560 laptop (SSD drive, UEFI, secure boot off).. Windows 10 > pre-installed, CentOS7 installed in a separate partition and running > for months w/o issue. Don't know what happened but at reboot yesterday > (not even booted in Windows, just rebooted), grub has disappeared, > booted in Windows by default, which apparently has taken over the UEFI > boot. The DELL XPS-13-9360 in its BIOS has an option (named "auto boot recovery" or similar - sorry the machine is somewhere else) that is by default enabled. I guess you have it enabled as well. This option is triggered by two unsuccessful boot trials, and leads to the loss of the grub menu, and restoration of the (non-grub) "Windows boot manager" (or whatever it's called). After being bit by it once, I disabled it. HTH, Kay P.S. I recovered my Ubuntu grub menu by booting from the Ubuntu live USB, and then sudo su mount /dev/nvme0n1p7 /mnt cd /mnt mount /dev/nvme0n1p1 boot/efi mount --bind /proc proc mount --bind /sys sys mount --bind /dev dev chroot /mnt grub-install /dev/nvme0n1 update-grub On CentOS, the last two lines would be grub2-install /dev/nvme0n1 grub2-mkconfig -o etc/grub2.cfg > > By booting from a USB drive w/ CentOS7 LiveGnome, I could use its grub > command prompt to inspect the UEFI of the local SSD drive, see that the > centos/ sub-directory and files are still there. > > /boot/efi/EFI/centos/: > BOOT.CSV > BOOTX64.CSV > fonts > grub.cfg > grub.cfg.1501243846.rpmsave > grub.cfg.1505469290.rpmsave > grubenv > grubx64.efi > mmx64.efi > shim.efi > shimx64-centos.efi > shimx64.efi > > maybe /boot/efi/EFI/Boot/ contents has been altered? > > /boot/efi/EFI/Boot/: > bootx64.efi > fbx64.efi > > I had a backup of the full efi partition (`dd`) but it's outdated and > I feel it's a bad idea to restore the partition from it. > > Still from this "external" grub prompt, I could boot into my CentOS7 > using: > configfile (hd0,gpt1)/EFI/centos/grub.cfg > > At least I know how to get back to it :-). > > But now, how could I give the UEFI control back to grub? Is there a > grub2 or grubby command I can run to make grub the default? I've read a > lot and still cannot figure out exactly what to do or don't dare > running commands that could make things worse. > > And I have the feeling the at next Windows boot, I may need to do it > again.. > > > Regards, > > > > _______________________________________________ > CentOS mailing list > CentOS at centos.org > https://lists.centos.org/mailman/listinfo/centos >