anhedonic

Live CD

For these instructions, you do not need a live CD. You will always be able to reboot into UEFI mode to fix any problems.

However, if you’re paranoid (like me), you’ll have a Live CD or USB handy. I recommend you come prepared.

Grub2

Fedora 18 splits Grub2 into two packages: one for UEFI and one for BIOS. We need to install the BIOS version.

These can exist side-by-side: yum install grub2

Partitions

Grub needs space for grub stage 1.5. Basically the Grub boot binary is too big for the traditional boot record for BIOS (the MBR) That boot record is only 512 bytes.

For traditional partition tables, Grub just used some scratch space, and the user never had to worry. For UEFI, the partition table is now a GPT partition table, and the user does need to worry. You need to create a BIOS Boot Partition. This is UEFI’s backwards compatible partition.

This partition only needs to be a few KB big. 1 MB is already too big. Depending on how Fedora was installed you might have to re-size your LVM volume. However, Fedora installs partitions aligned to MB boundaries for performance reasons, so you can usually squeeze one in the middle.

Use parted to do this. You want to end up with something like this:

(parted) print
Model: ATA LITEONIT LMT-256 (scsi)
Disk /dev/sda: 256GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:

Number  Start   End     Size    File system  Name                  Flags
 4      17.4kB  1049kB  1031kB               4                     bios_grub
 1      1049kB  211MB   210MB   fat16        EFI System Partition  boot
 2      211MB   735MB   524MB   ext4
 3      735MB   256GB   255GB                                      lvm

Here I created partition 4, and squeezed it in the beginning. Toggle the partition flag to bios_grub.

(parted) mkpart 4 0 1MB
(parted) toggle 4 bios_grub
(parted) quit

You do not need to format this partition. Therefore you also do not need to mount this partition. Grub will dump a binary to the beginning of this partition.

Bootable Partition

I didn’t need to do this, and I haven’t done this. However, some older BIOS-es will require a bootable partition.

You can’t use parted for this. You must use fdisk, and mark the GPT partition as bootable. I think it’s the ‘a’ option in fdisk (from memory)

Config File

Grub needs a configuration file. For BIOS this is /boot/grub2/grub.cfg For UEFI this was /boot/efi/EFI/fedora/grub.cfg

Grub2 wants you to use /sbin/grub2-mkconfig, and not manually edit a config file. This is what Grub2 wants, and it’s wrong.

/sbin/grub2-mkconfig will create a configuration file for the current boot environment. If you booted UEFI (like you would have), you end up with a UEFI grub.cfg, and not a BIOS grub.cfg.

So first make it: grub2-mkconfig -o /boot/grub2/grub.cfg, then edit it.

• Replace all instances of linuxefi with linux
• Replace all instances of initrdefi with initrd

Boot Record

Now we’re ready to install Grub on the MBR:

grub2-install --target=i386-pc /dev/sda # replace sda with your disk

The --target=i386-pc tells Grub to install BIOS files; and not UEFI files. It has nothing to do with 32bit vs. 64bit kernels.

BIOS setting

Reboot. Go to the boot menu, and find the option for OS type. This will be set to UEFI OS. Change it to CMS OS.

Reboot.