[CentOS] Analyzing the MBR

[mark]

On 06/05/14 07:01, Timothy Murphy wrote:
> Is there any tool for analysing the MBR on a computer?
> I know one can just dd it and see roughly what it contains.
> But surely one should be able to work out the exact content
> of the MBR and the neighbouring sectors read at boot time?
>
> I had a difficult day, probably due to my ignorance,
> which would have been solved at once by such a tool.
> I had taken one of three hard disks out of my home server
> (to see exactly what it was, as smartctl said it was not
> in its database) and this had the effect of altering
> the order of the disks in the BIOS, preventing re-booting.
<snip>

ARGH! I just had to deal with two servers that failed, and it took me two and 
a half *days*. Some things to take away:

1. Disconnect everything else that might be plugged in (like a RAID box on a 
controller that would let the system boot off it).
2. Go into the BIOS, and reorder the HDD so that the one you want it to boot 
off of is first.
   2.a. Don't assume, when you plug stuff back in, that the BIOS won't decided
	on its own to be "helpful" and reorder....
3. Linux rescue, fdisk -l
4. grub-install

	mark