Kernel update broke my system.

[Bruno Wolff III]

On Fri, May 29, 2009 at 13:27:50 -0500,
  "Smith, Herb" <herb.smith at boeing.com> wrote:
> Can't boot into anything when all you get is the GRUB_ prompt.  Wrote to
> the help me list to figure out what to do to get my system back.  Once I
> get it back I'll be able to try a lot of different things.  From the
> respones of some, it seems that it's an issue with GRUB, but it's
> unclear that there is an underlying kernel issue or not.  It would seem
> that the kernel might be ok, but just that GRUB got hosed in the update
> process. 

If you get the grub prompt, then you can issue a configfile command to
tell it where the config file is located. Typically it will be something like:
configfile (hd0,0)/grub/grub.conf

This assumes /boot is a separate (and first) partition of the first disk.

Once you have booted, you can fix this by running grub as root and then using
the following commands:

root (hd0,0)
setup (hd0)

And if you are using raid 1 and you want the second disk to be usable if
the first has been pulled, you can addition run:
setup (hd1)

(In the raid case there is supposed to be a way to tell grub to use the
current disk instead of a specific disk, but I don't think Fedora does
that by default, and the above is easier to remember and works well
enough for me.)

At the grub prompt you can run help and there is tab completion for commands.
This helps prompt your memory when you aren't expecting to use it ahead
of time.