Booting problem

Keith Powell keith at
Wed Oct 8 07:51:59 UTC 2008

Mark Haney wrote:
> Keith Powell wrote:
>> Karl, Mark.
>> I have solved the problem.
>> Recapping, the XP drive is plugged and jumpered as the master and the 
>> Ubuntu the slave.
>> If I have the master drive plugged in when installing Ubuntu, the 
>> partitioner correctly recognises the slave as 'sdb'. However, if I have 
>> the master unplugged, it calls the slave 'sda'. In my 'un-expert' 
>> opinion, this is in conflict with what it should be.
> Why should it be in conflict? In the mind of the kernel, the first drive 
> is always assigned /dev/sda whether it was originally that or not.  (Or, 
> back in the olden days /dev/hda).
> It will only be recognized as such if the master is connected.  I know 
> this sounds a bit counter-intuitive, but keep in mind the M/S jumper 
> only affects drive designations if there is more than one drive.  If 
> there is only one, the 'slave' designation doesn't apply.  Does that 
> make sense?
> Remember, the kernel will designate drives in the order they are seen. 
> With just one drive, it's the first (and only).  With 2 drives, it falls 
> back to asking which is Master, and tagging it /dev/sda.
>> So, I have installed Ubuntu with the master plugged in and it now works.
>> I expect, but am guessing here, that I could alternatively have 
>> installed Ubuntu with the other drive unplugged and edited grub/menu.lst 
>> to change sda to sdb.
> Yeah that would probably have worked. I've done that in the past with no 
> trouble.  But that's been ages ago.
>> There's just one thing which has happened, which I didn't want. Ubuntu 
>> appears to have installed its grub onto the XP drive MBR. I want to find 
>> out how to reinstall the XP MBR and change the Ubuntu one to the sdb drive.
> You know, I'd recommend leaving it as is.  It's much easier to make grub 
> see Windows than it is for XP to see grub.  (Or to pass the boot 
> sequence on to grub is maybe a better phrasing).
> Either way, whichever boot manager you load first will HAVE to know 
> about both operating systems.  Otherwise the OTHER OS will never be 
> 'bootable' from there.
> Make sense?

Thank you, Mark, for the explanation.

Yes, it does make sense. I had got the wrong idea, so you have cleared 
things up.

I'll leave the booting as it is.



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