how to fix grub

Dave Howorth dhoworth at mrc-lmb.cam.ac.uk
Fri Jun 18 14:39:06 UTC 2010


Goh Lip wrote:
> On Fri, 18 Jun 2010 21:27:21 +0800, Matthias Andersson  
> <matthias.andersson at pp1.inet.fi> wrote:
> 
> 
>> I have noticed during the last week a problem with grub, at startup it
>> stalls during the "loading grub" message if any of the two external
>> hard-drives are connected to a USB port. The grub boot menu is never
>> displayed.
>>
>> If none of the hard-drives are connected then grub loads up fine and
>> boots the system.
>>
>> I've tried to run update-grub but it hasn't had any effects on the  
>> problem.
>>
>> Cheers,
>> Matthias Andersson
> 
> 
> Yes, that's a common issue with external drives, more so with grub-legacy.  
> The reason being the lines having (hd0,x)
> and /dev/sdax changes easily (by bios) each time when booting up, causing  
> the "root" of the grub system to be wrongly identified.

Well, there may be a more fundamental issue. If the BIOS is set to allow
booting from USB devices and if it is set to give them priority over a
permanent disk (and that would normally be the case) then the BIOS won't
try to run grub, it will try to run whatever the USB gives it,
presumably whatever's in the MBR of the USB disk.

So the first thing is to set the BIOS to not boot from USB devices. Or
if the OP needs to be able to do that, then grub needs to be installed
on the USB disks.

Cheers, Dave

Cheers, Dave




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