can't change MBR

Bruce Dubbs bruce.dubbs at gmail.com
Sun Mar 27 10:17:04 PDT 2011


Andrew Benton wrote:
> On Sun, 27 Mar 2011 12:06:35 -0400
> "piper.guy1" <piper.guy1 at gmail.com> wrote:
> 
>> Hi,
>>
>> I'm almost finished LFS-6.7. I verified that grub works in section
>> 8.4.3 and LFS boots up without any hitches.
>>
>> But now section 8.4.4 requires the change to the MBR with the
>> 'grub-setup' command. But it just won't work for me. I getting
>> segmentation faults and syntax errors.
>>
>> root:/# grub-setup '(hd0)'
>> Segmentation fault
>> root:/# grub-setup /dev/sda
>> Invalid device `/dev/sda'.
>> Try `grub-setup --help' for more information.
>> root:/# grub-setup "/dev/sda"
>> Invalid device `/dev/sda'.
>> Try `grub-setup --help' for more information.
>> root:/# grub-setup '/dev/sda'
>> Invalid device `/dev/sda'.
>> Try `grub-setup --help' for more information.
>> root:/# grub-setup '\(hd0\)'
>> Invalid device `\(hd0\)'.
>> Try `grub-setup --help' for more information.
>> root:/# grub-setup '/(hd0/)'
>> Invalid device `/(hd0/)'.
>> Try `grub-setup --help' for more information.
>> root:/# grub-setup \(hd0\)
>> Segmentation fault
>>
>> What am I doing wrong?
>>
> I'm going to guess that you've re-entered chroot and haven't
> mounted /dev in the chroot environment. So in chroot /dev/sda does not
> exist? Just a wild guess.

Andy, that would be my first guess too.  However, just leaving chroot 
and reentering does not automatically unount all the virtual mounts we 
did in section 6.2.  They would have had to have been umounted manually 
or a machine reboot for that to happen.

If that is the case, I think there is a bug in grub2 that returns a seg 
fault.  It should fail more gracefully if there is a problem.

   -- Bruce



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