UEFI Firmware

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Revision as of 20:35, 5 June 2011 by Kevmitch (Talk | contribs) (Enabling UEFI boot in Debian)
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UEFI Firmware

UEFI (Unified Extensible Firmware Interface) is a modernized replacement to BIOS (Basic Input/Output System). The specification is maintained by the collaborative non-profit UEFI Forum. UEFI is supported by both recent versions of both Linux and Windows. UEFI firmware with legacy BIOS support has started appearing on Sandybrige (220,420,520,etc.) Thinkpads. On supported machines, the firmware configuration utility (Thinkvantage->F1 on machine starup) has the option of enabling one or both UEFI/BIOS as well as providing the option to specify the order with which the machine tries to boot.

Current Status

Though the specification has been around since the late '90s, UEFI only recently started appearing on commodity hardware. Macs are a slight exception, though they do not strictly adhere to the UEFI standard. Linux can boot as usual in BIOS mode, however the ELILO boot loader or recent versions of Grub 2 are necessary to boot in UEFI mode. Linux 3.0-rc1 is reported to successfully boot in UEFI mode (details below), but older versions hang after the kernel gets loaded by grub.

Enabling UEFI boot in Debian

The following are steps to successfully boot in pure UEFI mode ("UEFI only" startup config menu). There are likely some that are redundant or unnecessary.

  1. Install 64-bit Debian in BIOS mode to an MBR partitioned disk.
  3. Create a small ~ 200MB Partition formatted to fat32 and enable the "boot" flag. The first partition is likely a good choice, but may not be strictly required. The "boot" flag is also likely superstitious.
  4. Burn some form of live cd that allows you access your Debian install in case something goes wrong and you are unable to boot.
  5. Mount the fat32 partition at /boot/efi
    sudo mkdir /boot/efi
    sudo mount /dev/sda1 /boot/efi
  6. Install the efi version of grub
    aptitude install grub-efi-amd64
  7. Now run grub-install (ignore warnings about efivars)
    sudo grub-install /dev/sda
    sudo update-grub
  8. This should have created /boot/efi/efi/debian/grubx64.efi. In order to make this actually work without running efibootmgr, just copy it to /boot/efi/efi/boot/bootx64.efi
    sudo cp /boot/efi/efi/debian/grubx64.efi /boot/efi/efi/boot/bootx64.efi
  9. Create the directories structure /boot/efi/efi/boot
    sudo mkdir -p /boot/efi/efi/boot
  10. Copy the grub.efi executabe into the efi partition
    sudo cp /boot/grub/grub.efi /boot/efi/efi/boot/bootx64.efi
  11. Reboot, enter the Thinkvantage menu and set "UEFI only" or "UEFI First". Hopefully you still get a grub menu and it will actually boot the 3.0 kernel.