How to restore MBR on a separate /boot partition?

[Dan Thurman]

On 04/08/2013 11:02 AM, Bill Davidsen wrote:
> Dan Thurman wrote:
>>
>> Since I was unable to install F18, I would like
>> to revert back to F17 that I have restored from
>> backups, the following partitions:
>>
>> / (root)   /dev/sda10
>> /boot      /dev/sda9
>>
> Did you make a physical backup of the partitions with dd or just back
> up the files on them? Yes it makes a difference in recovery...
I use rsync to save a backup of both partitions on another drive (both /
and /boot),
then I reformatted the sda9/10 in prep for F18.  Having failed to
install F18, I then
rsync from sdb9/10 back into sda9/10.  I just forgot how to use Grub2
exactly in order
to restore MBR on sda9.  I have done MBR installs many times before but
it has been
awhile for grub2!
>
>> What I have left to do is to restore the MBR
>> on /dev/sda9 /boot partition.
>>
> MBR isn't on a partition, that may be your issue.
That is exactly the issue.  I need the proper setup to mount,
chroot & grub2-install in order to install MBR onto sda9 to make
the partition(s) "seen" by grub.
>
>> I have a separate MBR installed on /dev/sda
>> drive which is the master MBR for multiboot
>> OS, which is working fine.
>>
> MBR means "Master Boot Record," so "master MBR" seems like something
> from the department of redundancy department. And if it's working fine
> I really don't understand your problem.
Right.  You can install MBR onto a partition as well as the whole drive.
>
>> What steps can I use to accomplish this?
>>
> Could you clarify "this" a bit, in terms of what you hope to
> accomplish, rather than how you are trying to do it? I'll try to help,
> and there are at least two people on this list who are better at boot
> issues than I am, so you can probably get a solution once we have an
> idea what you are trying to do.
>
As I barely recall, for OSes using grub2, for F17, I have to boot
LiveCD or DVD, mount the F17 (root & boot) partitions, chroot to
the mount point, and then run grub2-install with the correct
arguments. These are the details I am looking for.

For example, If one is using grub1 based partitions, it is a simple task:

# To find your GrubX boot partitions:
grub1

grub1> find /grub/stage1 ### to locate grub-1 boot partitions
  (hd0,4)    ### This partition is the "MBR" for the drive, sda (this is
my master grub list)
  (hd0,6)    ### This partition is the "MBR" for F13 (shows grub kernels)

grub1> find /grub/grub.cfg  ### to locate grub2 partitions
  [hd0,8]    ### This partition is the "MBR" for F17 (is missing cuz it
is not yet setup)
  (hd0,10)  ### This partition  is the "MBR" for Ubuntu-10

# To setup Grub-1 "MBR":
grub1> root (hd0)        ### sda (whole drive)
grub1> setup (hd0,4)
grub1> root (hd0,4)      ### sda5 partition
grub1> setup (hd0,4)
grub1> root (hd0,6)      ### sda7 partition
grub1> setup (hd0,6)

grub1> quit

But one cannot use grub1 to install grub2 based partitions
as explained above.

I hope this is clear (as mud?) ;)