Grub2 with RAID+LVM no longer fits in 62 sectors

[zeukiller]

Hi,
During installation of Ubuntu 12.04, I can not finish the installation correctly, because the installation of grub goes wrong.
Indeed, during the installation of grub I have a recurring error as follows:
/usr/sbin/grub-setup: warn: Your embedding area is unusually small. core.img
won't fit in it..
/usr/sbin/grub-setup: error: embedding is not possible, but this is required
when the root device is on a RAID array or LVM volume.

I'm running on 64bits plateforme, with LVM over RAID partitions. The same installation works perfectly with Ubuntu 10.04.3 LTS.
Here are more informations about my partitions : http://paste.ubuntu.com/1003855/

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Phillip Susi (psusi)]

It appears that the size of the grub2 core image when raid and lvm modules are included has increased slightly since 10.04, and no longer can fit in 62 sectors. It is now the norm for partitions to be aligned to a 1 MiB boundary, leaving 2047 sectors for the embed area, but your partitions start on sector 63 instead.

[zeukiller (zeukiller)]

Hi,
And thanx for the answer.
So if I understand correctly what you said, I must increase the size of my boot sector from 62 to 2048 ?
Is it possible ? and how ? ... it sounds a little bit risky, no ?

[Phillip Susi (psusi)]

It is not done easily. You should be able to do it with a livecd using gparted, but it will take a very, very long time since it has to move all of the existing data, and a crash in the middle would result in a total loss. The best way to do this is to backup the whole system, format, and restore.

[zeukiller (zeukiller)]

Hi,
and thanx a lot for the tips.
I think about it, and I think ...I've got RAID 5, I can remove a disk from the array, format it correctly (with a huge boot sector :p) and re-add it to the array.... So I will be able to install grub at least on that disk, what do you think about this ?
Thanx

[Phillip Susi (psusi)]

That might work, or the disk may not fit back into the array with the slightly reduced size.

[zeukiller (zeukiller)]

Hi,
yeah, you're right, I can't add the disk to the array.
I installed Ubuntu on an other disk and it works.
Thanx a lot.