EFI booting?

Kate Monster · Posted: Fri Jun 22, 2012 2:19 pm Post subject: EFI booting?

hi,

I got a new computer. This new computer has an SSD and EFI, two technologies I've never worked with before. So of course, I first thought of Gentoo. I got new hardware, now it's time to run it through it's paces :twisted:

Anyway, EFI is giving me a lot of trouble. I installed grub2 with GRUB_PLATFORM="efi-x86_64" and read a couple guides, but I'm still confused. So if I understand correctly, in order to get a boot-able system, I first need to be booted into an EFI compatible Live CD? Or was that some extra unnecessary step? I'll post the guides I used later, but I'm at work right now. I really would like to get a working system tonight, so I can get my emerge -e world running. If I need my system booted via EFI to be able to setup my boot loader, what is a good CD to use?

srs5694 · Posted: Fri Jun 22, 2012 5:41 pm Post subject:

It's usually possible to install in BIOS mode and switch to EFI mode later, or to just ignore EFI and use BIOS mode entirely. That said, in the long run using EFI mode can have some advantages, such as faster boot times (on some, but not all, systems), a different selection of boot loaders (which can be a plus or a minus, depending on your needs and preferences), saner boot loader management, and so on.

If you want to install in EFI mode from the start, you could use an Ubuntu CD in its "try it before installing" mode. Those CDs generally boot pretty well in EFI mode, and you can then follow the usual Gentoo installation method. Check for a /sys/firmware/efi directory after booting. If it's present, you've booted in EFI mode. If it's absent, you've probably booted in BIOS mode, although there are ways to boot in EFI mode and not have that directory, so this condition isn't absolute proof of a BIOS-mode boot.

IMO, GRUB 2 is the worst of the available EFI boot loaders, so my advice is to avoid it. In my experience, the kernel's EFI stub loader is the most reliable of the EFI boot loaders, but it has no user interface. You'll need to add it to your firmware and use its boot manager to select which kernel or OS to boot or use some other boot manager (such as rEFInd) to select the kernel or OS to boot. Fedora's patched GRUB Legacy and ELILO are two other options that work better than GRUB 2, in my experience. See my Web page on the topic for more information on EFI boot loaders, including my detailed comments about each of them and installation instructions. Note that booting in EFI mode is required to add the NVRAM entries that are the official standard way of booting, but you can set a default by using a specific filename (EFI/boot/bootx64.efi on the ESP) instead, and you can do this even from a BIOS-mode boot. The catch is that if something else has set an NVRAM entry for the boot loader, using the default name is unlikely to work.

Kate Monster · Posted: Fri Jun 22, 2012 5:54 pm Post subject:

khayyam · Veteran Joined: 07 Jun 2012 Posts: 1241

Kate Monster · Posted: Sat Jun 23, 2012 2:30 am Post subject:

khayyam · Veteran Joined: 07 Jun 2012 Posts: 1241

Kate Monster · Posted: Sat Jun 23, 2012 2:16 pm Post subject:

khayyam · Veteran Joined: 07 Jun 2012 Posts: 1241

Kate Monster · Posted: Sun Jun 24, 2012 5:45 am Post subject:

khayyam · Veteran Joined: 07 Jun 2012 Posts: 1241

gemarcano · n00b Joined: 04 Jun 2012 Posts: 34 Location: New York

I don't know if this is solved or not, but I'll add my two cents since I did try to get GRUB2 to work on an UEFI system. In the end I gave up with GRUB2 and resorted to booting from rEFInd. I did experiment with the kernel stubs (and they WORK really well), so I'll share a few of the problems (and solutions) I ran into along the way (not many). Forgive me if these suggestions sound simple-- I'm just a simple individual, and at one point these "simple" points were mountains in my view.

-First of all, I didn't use a flash drive to install in EFI mode. I simply burned a Fedora 17 CD (make sure to boot it in EFI mode) (I tried making it into a USB Flashdrive image but it failed miserably, even with Fedora's own tools for it) and then followed the Gentoo Handbook for amd64 (in my case). I also used this blog entry as help.

-In regards to the instructions from the blog, I do not have any framebuffer stuff enabled because I use KMS (nouveau driver), and I can still boot fine, BUT I do see some graphic artifacts (a bunch of yellow lines) for a split second a the beginning of boot, may be related to the framebuffer.

-Once the new kernel was compiled and installed (make && make_install && make modules_install), I simply copied the vmlinuz image from /boot to /boot/efi/EFI/Gentoo/ (NOTE: /boot/efi is where I mounted my FAT32 EFI System Partition, your mount point may vary).

-While on the topic of the EFI System Partition (ESP), it seems some UEFI implementations (and Windows, but you might not care about this) are finicky about the format for this partition, as well as its location. The recommended location for it is the first partition (size anywhere between 100 to 200 MB, or whatever, just large enough to fit all of your bootloaders), and things all seem to favor FAT32 over FAT16 (in other words, if you use mkfs.vfat to make a FAT32 partition, make sure to specify the -F32 parameter).

-I passed kernel parameters by building them into the EFI entry through efibootmgr, through something like this:

keet · Guru Joined: 09 Sep 2008 Posts: 330

I've had a U.E.F.I. motherboard for over a year, and I just got an S.S.D., plus I've reinstalled Windows a couple times, so I've been through reinstalling G.R.U.B. 2 in U.E.F.I. multiple times. Usually I just boot GRUB using an UEFI Ubuntu disc, use the GRUB command line to boot into Gentoo, and reinstall GRUB 2 in the UEFI. It's not that difficult once you've done it half a dozen times.

_________________
My Gentoo computers:
Home-built i7 2600K / 8GB RAM || Dell T6400/4GB RAM
Panasonic Toughbook CF-51 T2300/4GB RAM || Fujitsu Lifebook P4/1.6Ghz, 512MB RAM

WorBlux · n00b Joined: 07 May 2011 Posts: 25

You don't actually need a liveCD booted in UEFI mode to get it to work.

If you copy the UEFI shell onto the UEFI system partition your boot menu will let you load it. You can then boot any .efi executable you have on that partition, (grub, rEFInd, the kernel with EFI_STUB). So long as you compiled the gentoo kernel with support for the /sys efi variable interface you can use efibootmgr to finish.