In short, PREEMPT_RT disabled EFI runtime, meaning efibootmgr does not work. GRUB uses efibootmgr to set the UEFI boot loader to itself and manages this internally by `grub-install`
1.) Set `efi=runtime` on kernel command line (not required if using systemrescuecd) 2.) Boot into Debian. If you do not have access to the Debian system due to boot loader not being installed correctly or missing, then: 2b.) Boot systemrescuecd 2c.) Mount Debian root filesystem, EFI partition and boot partition. i.e. /dev/sda1 - 100MB - EFI system partition (/efi) /dev/sda2 - 2GB - Linux filesystem (/boot) /dev/sda3 - 100GB - Linux root filesystem (x86-64) (/) With the above partition layout (`fdisk -l` to print current table) chroot and mount like so: mkdir -p /mnt/debian mount /dev/sda3 /mnt/debian mount /dev/sda1 /mnt/debian/efi mount /dev/sda2 /mnt/debian/boot mount -t proc none /mnt/debian/proc mount --rbind /dev /mnt/debian/dev mount --rbind /sys /mnt/debian/sys mount --bind /run /mnt/debian/run chroot /mnt/debian /bin/bash source /etc/profile && ldconfig Note `bind` for /run and `rbind` for /dev and /sys this is so /dev and /sys and mounted recursively (i.e. /sys/firmware and /sys/firmware/efivars are mounted too) 3.) Install GRUB with UEFI: grub-install --target=x86_64-efi --efi-directory=/efi 4.) Generate GRUB config file: grub-mkconfig -o /boot/grub/grub.cfg Change EFI path and all partitions accordingly. Alec _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
