Feb 182010
 
 February 18, 2010  Posted by at 11:44 pm documentation, hardware Tagged with: , , , , , , , ,  Add comments

Recently, I was installing debian on a new server and grub2 would not install gave me this error:

“This GPT partition label has no BIOS Boot Partition; embedding won’t be possible! grub-setup: error: Embedding is not possible, but this is required when the root device is on a RAID array or LVM volume.”

Of course, it being grub2, I jumped to the conclusion that grub2 was the problem. I installed legacy grub and got nowhere.
Doing the usual
grub> root (hd0,0)
grub> setup (hd0)
produces this error:
“file /boot/grub/stage1 not read correctly”

No matter what I did, it would not install. So, I went back to the original message and gave grub2 its due process. Turns out this Dell T410 uses GPT (GUID Partition Table) which is an extension of EFI. The “BIOS Boot Partition” is an actual partition on the hard drive. Grub2 embeds the core.img (multiboot boot kernel) into this BIOS boot partition instead of the MBR.
Here are two great resources on this subject:
http://www.rodsbooks.com/gdisk/index.html and
http://grub.enbug.org/BIOS_Boot_Partition

So, the solution:
I had to re-install Debian with a small partition. Apparently it can be under a few hundred KiB. Space is cheap and I didn’t want to have more problems, so I made mine 5MB and put it at the beginning of the disk. In the Debian partitioner, set the partition under “use as:” to “Reserved BIOS boot area“. Then continue with the rest of your partitions and install. Grub2 installed with no problems this time!

If using an older version of Debian, lenny (v5) or older. The “use as:” does not have an option for Reserved BIOS boot area. So, I booted into expert install mode, when you get to “Load installed components from CD” select parted. This will install parted in the install environment. Before you get to detect disks, do ctrl+alt+f2. On the command line you can manually create a bios boot area.

The following parted commands.

parted -a optimal /dev/sda mkpart 1 1 6

The above command creates the first (1) partition from 1MB of the drive to 6MB. -a optimal sets the block alignment for best performance. If you start the partition at 0 the alignment is wrong and parted will Warn: “The resulting partition is not properly aligned for best performance. Ignore/Cancel?”

parted /dev/sda set 1 bios_grub on

This sets /dev/sda1 as GPT grub bios partition. This partition will be found and used by grub on install.

Now, ctrl+alt+f1, and continue the install. Select manual partitioning and be sure not to delete the primary partition (gpt, grub bios) when creating your new partitions.

Do this to all drives in a raid!

After you boot into the fresh install, you can manually install to the other disks.

grub-install /dev/sdb

Now its installed on sda and sdb. In case sda fails, it should be able to boot from sdb.

 

  One Response to “* Transition away from MBR to GPT booting”

  1. Thank you! This really should be in a man page somewhere. I’ve been using MBR partitions because of this limitation of GPT.

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