preupgrade grub2 failed: now can't boot

[Alan Cox]

On Mon, 06 Feb 2012 18:49:19 -0700
Greg Woods <woods at ucar.edu> wrote:

> On Mon, 2012-02-06 at 19:48 -0500, sean darcy wrote:
> 
> > grub2-install --no-floppy /dev/sdg
> > /sbin/grub2-setup: warn: Your embedding area is unusually small. 
> > core.img won't fit in it..
> > /sbin/grub2-setup: warn: Embedding is not possible.  GRUB can only be 
> > installed in this setup by using blocklists.  However, blocklists are 
> > UNRELIABLE and their use is discouraged..
> > /sbin/grub2-setup: error: will not proceed with blocklists.
> > 
> > What do I do now! Embedding area???
> 
> This is the area at the beginning of the disk, before the first
> partition. Grub2 needs the first partition to start at 2048, but default
> partition layouts from Grub-1 systems start at 63. I have run into this
> several times and it is a royal pain. There may be some games you can
> play with gparted (shrink the partition, then move it), or you can do
> like I did, which is to dump the first partition, change it to start at
> 2048 (shrinking it a bit), making a new file system on the new
> partition, and restoring it.

Welcome to grub2 - it's as you've discovered completely awful (and a look
through the huge pile of crap scripts Fedora has spewed to try and hide
it is even more painful). You can do two things

1. Replace it with the old grub, which will need you to hand set up the
/boot/grub* files as before and just work.

2. Mess around backing up the entire system, repartitioning and the like.

3. Tell it to STFU and use blocklists, in which case it'll work fine in
my experience but has the same limits as grub1 (*don't* try things like
defragging /boot or putting /boot on btrfs)

The fact Fedora didn't properly test such basic upgrades in FC16 is a
symptom of how bad the Fedora QA has become unfortunately.

Alan