UEFI on Gentoo w/ grub2 and GPT

I did this on a new build (new hard drive) on a current slave system. So you can adapt the techniques a bit if you're doing this off a livecd or just migrating a current system.

First you'll want to download a UEFI compatible livecd ( or make your own ). I recommend SysRecueCD http://www.sysresccd.org/Download based on Gentoo. Just download the iso and burn it to a cd, then  set it aside.

You'll want to build a EFI partition either using parted or gdisk (assuming this is a clean disk, add your other partitions into this string of commands like normal): gdisk /dev/sdX Command (? for help): n Partition number (1-128, default 1): 1 First sector (34-3970014, default = 2048) or {+-}size{KMGTP}: Last sector (2048-3970014, default = 3970014) or {+-}size{KMGTP}: +250MB Current type is 'Linux filesystem' Hex code or GUID (L to show codes, Enter = 8300): ef00 ( note : this part is only if you want to have a legacy mbr/non-uefi boot option for whatever reason ) Command (? for help): x Expert command (? for help): a Using 1 Known attributes are: 0: system partition 1: hide from EFI 2: legacy BIOS bootable 60: read-only 62: hidden 63: do not automount Toggle which attribute field (0-63, 64 or <enter> to exit): 2 Have enabled the 'legacy BIOS bootable' attribute. Attribute value is 0000000000000004. Set fields are: 2 (legacy BIOS bootable) Toggle which attribute field (0-63, 64 or <enter> to exit): Expert command (? for help): p ... Expert command (? for help): w Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING PARTITIONS!! Do you want to proceed? (Y/N): y

Add this line to your make.conf (or modify for your arch needs) :
GRUB_PLATFORMS="efi-32 efi-64 emu pc"

Then emerge efi/grub2:
emerge -av efibootmgr grub:2

Create the filesystem (has to be fat): emerge -av dosfstools mkdosfs -F 32 /dev/sdX1

If you want to have a legacy  boot loader on this drive then I'd recommend using a directory inside of /boot ( like /boot/efi ) for the efi partition. Otherwise you can use /boot. mkdir /boot/efi mount /dev/sdX1 /boot/efi mkdir -p /boot/efi/{EFI/BOOT,GRUB2}

You'll probably want the following options enabled in your kenerl : Processor type and features ---> [*] EFI runtime service support [*] Build a relocatable kernel Device Drivers ---> Graphics support ---> <*> Support for frame buffer devices ---> [*] Enable firmware EDID [*] EFI-based Framebuffer Support Console display driver support ---> <*> Framebuffer Console support Firmware Drivers ---> <*> EFI Variable Support via sysfs -*- enabler the block layer ---> Partition Types ---> [*] Advanced partition selection [*] EFI GUID Partition support

Compile your new kernel, then copy over your vmlinuz/bzimage to /boot : cd /usr/src/linux make; make modules_install cp /usr/src/linux/arch/x86_64/boot/bzImage /boot/kernel-3.7.7
NOTE: kernels must be in the following format for grub2 to autodetect "kernel-(version)" or "vmlinuz-(version)"

Make the config file with grub2 :
grub2-mkconfig -o /boot/grub2/grub.cfg

Now if you're currently booted off a UEFI medium, then great. Otherwise you need to use the sysrescuecd linked above or another medium. Reboot and check your BIOS settings. I am running a Sabertooth 990fx r2.0 and changed: Boot -> CSM parameters -> Launch CSM : Enable Boot Device Control : UEFI Only Boot From Storage Device : UEFI Driver first Boot -> Secure Boot pamareters -> Select "Other OS"

That forced the board to only boot of UEFI so I knew that the livecd wouldn't be booted in legacy/mbr mode. After you're booted off a uefi medium you can verify by looking for the directory `/sys/firmware/efi` .

If it exists you should be good. If it doesn't then you either :
A) Aren't booted right off the UEFI medium - check bios settings
B) Check livecd you're using to make sure it supports efi bootmgr and the kernel
C) modprobe efivars - if the kernel built it in as a module

You shouldn't have to worry about B or C if using the sysrescd.

Get back in your new build environment if you had to reboot mkdir /mnt/tmp mount /dev/sdX2 /mnt/tmp mount -o bind /dev /mnt/tmp/dev mount -t proc none /mnt/tmp/proc mount -t sysfs none /mnt/tmp/sys chroot /mnt/tmp /bin/bash --login env-update;source /etc/profile mount /boot/efi

Finally install the EFI grub bootmgr : grub2-install --target=x86_64-efi

It should tell you if it was successful. If so - reboot off your new UEFI grub2 disk!

You may want to go back into your BIOS if you enabled UEFI only mode, and put it into mix mode in case you ever want to boot off a non-uefi medium.