Linux on an Apple Xserve EFI only machine

We have a few of these Apple Xserve machines at work which weren’t doing much, so I thought I’d make better use of them. Naturally, this meant installing Linux on them.

These machines do not have a BIOS (or even any emulation), they use EFI and as such won’t boot the standard Linux install media. I knew that Fedora could boot EFI, so that’s where I started, with Leonidas (version 11). Unfortunately, the install media just wouldn’t work on this device, presumably as it has no BIOS emulation.

To cut a long story short, I had to learn how EFI works in order to get it booting and it wasn’t an easy thing to discover!

Booting EFI
In short, the Apple EFI boots and scans all available drives (including USB drives) for a GPT partitioned device which has a FAT formatted partition on it. Inside this partition it looks for an efi directory.

In that directory must be another from the list of approved vendor named directories, such as redhat or apple. The default is boot and this is what I used.

Inside that boot directory, EFI looks for a binary EFI file, which it can run. In my case, this is a GRUB2 EFI binary. The name of the file must match your architecture, so for me it is called bootia32.efi but if you’re running a 64bit system it should be bootx64.efi.
NOTE: Your Mac must have a 64bit EFI to load the 64bit EFI Linux installer (bootx64.efi)). Else, try choosing the 64bit options when using the 32bit EFI installer (bootia32.efi), but either way your system must have a 64bit CPU.

The GRUB2 EFI binary I am using looks for the standard GRUB config file, which is called grub.cfg. This must also be in the efi/boot/ directory of the USB device. The kernel and initramfs for the net installer should also be in that directory.

I have made a Debian Squeeze, Fedora Constantine and Ubuntu Karmic installer which you can download and extract onto your USB device (sha1sum). You will still need to partition and format your device, so more on how to do that later.

Partition USB Boot Device
So, once we understand how EFI works, next we need to get a bootable GRUB happening in order to install Linux.

Grab a USB memory stick and let’s prepare it. Please know what device it is you’re partitioning!! I’ll use sdz just for example purposes only.
Unmount it
su -c 'umount /dev/sdz1'

Partition and format it
Partition and format it
su -c 'parted -s /dev/sdz mklabel gpt mkpartfs EFI fat32 0% 100% toggle 1 boot'

It should now automatically mount. If not, unplug it and plug it in again, or mount it manually.

Prepare USB Boot Device
Next you can extract my tarball onto the device, ensuring that it maintains the efi/boot/ directory structure on it and not create an extra directories because of the archiver. If it’s not right, then re-arrange things and eject the device.

You should now be able to plug it into your Xserve and turn it on.

Hold down the Option key (Alt key on non-Apple keyboards) until you see the boot option. It should show “EFI” on the usb stick. Boot this and you should see the GRUB menu load. Choose the distro you want to install and away you go! See the “Installation” section below and skip the next few.

Manual preparation – Building GRUB2
Before we can compile GRUB, we need some dependencies. If you’re using Debian or Ubuntu, then run the following:
sudo apt-get build-dep grub2
sudo apt-get install libusb-dev

We need to check out GRUB from CVS and build it for EFI systems. Note, my Xserve is 32bit only, so I’m installing 32bit version. If you’re using 64bit then use a 64bit OS. You can cross compile, see the link above for info if you need to.

Check out source from CVS:
cvs -z3 \
-d:pserver:anonymous@cvs.savannah.gnu.org:/sources/grub \
co grub2
cd grub2

Or get source from Debian (which is more likely to compile):
apt-get source grub2
cd grub2*

Build grub2:
./configure --with-platform=efi
make

Now, make a temporary directory in which to put the GRUB EFI binary.
mkdir -p efi/boot/

Next we need to create the GRUB2 EFI program, and will specify a bunch of modules to include. This was a big stumbling block for me because someone removed the ability to read config files from module “configfile” and put it into “minicmd” requiring “sh”. The documentation I was following was not updated and I couldn’t work out why GRUB2 couldn’t parse my config (typing it in manually at the GRUB2 command prompt worked however). After lots of wasted time I emailed the GRUB list and had an answer within 20 minutes, which was a big relief.

./grub-mkimage -d . -o bootia32.efi part_gpt hfsplus fat ext2 normal sh chain boot configfile minicmd linux loadbios reboot appleldr halt search
sudo cp bootia32.efi efi/boot/

The efi/ directory now just needs to be copied onto your FAT USB stick. Don’t forget to make sure the directory structure is correct, as laid out above.

Now you just need to create a GRUB2 config file, which we’ll do below after getting the kernel and initramfs.

Manual preparation – Linux installers
I am using the netboot installers for each distro. This basically consists of a kernel, initramfs (which includes the installer). To know how to boot these in the GRUB config file, I read the isolinux configs included on the install CDs.

So, download the network installer of your choice in ISO format. Mount loop it and copy the kernel and initramfs onto the efi/boot/ directory on your USB disk.

For example (32bit), Ubuntu, Fedora, Debian Squeeze (note that Fedora does actually have an EFI boot disk which you can dd directly to a USB stick and boot, however this didn’t work on my Xserve but it might be useful to grab the kernel and initramfs from as it’s smaller).

Mount loop ISO:
mkdir /tmp/iso
sudo mount -o loop boot.iso /tmp/iso

Copy the kernel and initramfs from /tmp/iso onto your USB stick. You might need to look at the isolinux.cfg files under /tmp/iso in order to find out which is the kernel. On Debian and Ubuntu the kernel is called linux and the initramfs is called initrd.gz, both in the root directory.

GRUB Config File
Now that you have the GRUB2 EFI binary (bootia32.efi), kernel and initramfs on the USB stick, we need a config file for GRUB to read when it loads.

Here is an example for all four distros that I use in my provided tarball.
set timeout=10
set default=0
menuentry "Debian Squeeze" {
linux /efi/boot/linux-squeeze priority=low vga=normal video=efifb
initrd /efi/boot/initrd-squeeze.gz
}
menuentry "Fedora Leonidas" {
linux /efi/boot/vmlinuz-leonidas nomodeset xdriver=fbdev noselinux
initrd /efi/boot/initrd-leonidas.img
}
menuentry "Ubuntu Jaunty" {
linux /efi/boot/linux-jaunty priority=low vga=normal video=efifb
initrd /efi/boot/initrd-jaunty.gz
}
menuentry "Ubuntu Karmic" {
linux /efi/boot/linux-karmic priority=low vga=normal video=efifb
initrd /efi/boot/initrd-karmic.gz
}

Note that for Fedora I had to turn kernel based mode-setting off, and specify the Xserver driver.

The USB keyboard just wouldn’t work on either Ubuntu, but Debian Squeeze worked fine. I ended up choosing Fedora.

Manual preparation – Install Linux
Once you have all the required files, plug the stick in and turn on the Xserve. Hold down the Option key (Alt key on non-Apple keyboards) until you see the boot option. It should show “EFI” on the usb stick. Boot this and you should see the GRUB menu load where you can boot your network installer of choice.

Installation
When installing, you need to follow the same partition structure as the USB stick. I completely blew away all Apple partitions and am booting only Linux. The drives need to be GPT and to have a small FAT partition at the beginning with the efi/boot/ directory, GRUB2 EFI binary, GRUB config, kernel and initramfs.

There’s probably a better way to do this, I’m sure some distros will support GRUB2 and EFI out of the box soon. In the mean time I install the OS without a boot loader and create the efi/boot/ system manually. This means every time you update your kernel, you need to copy the kernel and initramfs, and update the GRUB config file.

The config file should be the same as the one used on the USB stick, except that the names of the kernel and initramfs will be different. For example:

set timeout=10
set default=0
menuentry "Fedora Leonidas" {
linux /efi/boot/vmlinuz-2.6.28-13-generic nomodeset xdriver=fbdev noselinux root=/dev/sda3 ro
initrd /efi/boot/initrd.img-2.6.28-13-generic
}

Conclusion
These are some rough notes to hopefully help others out there trying similar things. Please let me know how it works for you. I installed Fedora on my Xserve and it’s running quite well!

151 Responses to “Linux on an Apple Xserve EFI only machine”


  • Kind of sounds like it’s trying to load a legacy (non-EFI) bootloader.

    These days distros like Fedora/CentOS support UEFI directly, maybe installing something like that (without even rEFInd) might be a possibility?

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