Creating EFI boot for an already installed linux

Question

The issue is twofold:

• The project and its software requires Scientific Linux 6.8, which only supports setting up MBR boot during installation. (unless I missed something)
• The laptop does not support legacy boot, so requires EFI.

So now I'm sitting here with a 200Mb partition with the boot and esp flags on it, but I'm stumped: What's next? How do I set up this partition to boot into SL6.8? Are any changes needed to the OS itself?

Partition details:

/dev/sda1       /home (ext4)
/dev/sda2       /     (ext4)
/dev/sda3       swap
/dev/sda4       /mnt/shared (vfat partition)
/dev/sda5       ? (EFI partition, leftover from a linux distro that supported this during installation for testing.)

PS: I know the combination of this works, as it used to have both SL6.8 and EFI boot before the harddrive died. No idea who set it up, or how.

PS: Reinstallation of the linux distro is an option, but I don't think that's needed?

I will gladly post more details if needed.

Answer 1

Grub2 supports efi. You could install grub2. Heres a detailed wiki post from ubuntu about it. https://help.ubuntu.com/community/UEFIBooting

Install GRUB2 in (U)EFI systems

Boot into Linux (any live ISO) preferably in UEFI mode.

Determine your EFI SYSTEM PARTITION or create it (>=100 MiB FAT32 partition - GPT fdisk type code EF00 or GNU Parted 'boot' flag in GPT).

Mount the partition at /mnt/EFISYS (or at any mountpoint you wish). The following code assumes /dev/sda1 to be EFISYS partition.

sudo mkdir -p /mnt/EFISYS # if the mount-point does not exist
sudo modprobe dm-mod # required to make grub-probe stop complaining
sudo mount -t vfat -o rw,users /dev/sda1 /mnt/EFISYS
sudo mkdir -p /mnt/EFISYS/efi/grub

Then, build an EFI application for GRUB and copy it and the other modules:

cd <grub2_compiled_source_dir>/grub-core
../grub-mkimage -O ${EFI_ARCH}-efi -d . -o grub.efi -p "" part_gpt part_msdos ntfs ntfscomp hfsplus fat ext2 normal chain boot configfile linux multiboot
sudo cp grub.efi *.mod *.lst /mnt/EFISYS/efi/grub

Note : The -p "" option is important for creating a portable grub.efi app. Now create a grub.cfg in /mnt/EFISYS/efi/grub :

sudo touch /mnt/EFISYS/efi/grub/grub.cfg