UUIDs on drives

[Derek Broughton]

ghe wrote:

> Mario Vukelic wrote:
> 
>> "Used to" being the instrumental expression.
> 
> Yup. Worked at point A, didn't at point B. A popular description for
> that condition is "broken".
> 
>> Yes, that was back then. As I understand it, now that we have SATA and
>> whatnot, this is simply not guaranteed by the hardware anymore.
> 
> Nope. The hardware has *got* to be consistent in its self description.
> Otherwise the OS's be writing to disk locations at random.

I don't see that the two statements are contradictory.  The _hardware_
identifies itself - but the hardware never identified itself as /dev/sdb3. 
The software does that...
> 
> On my machine, there are 4 places to plug in SATA disks, and 32 possible
>   locations on the SCSI bus. Number 1 SATA connector is number one SATA
> connector always and forever. It's called sda when there's nothing found
> on the SCSI bus. If there's a SCSI disk, that becomes sda, and SATA
> connector number one becomes sdb -- it's the software that labels them,
> the software is written by humans, and they can have it label the number
> one SATA connector with a random number generator or not, it's up to them.

But why would they want to make artificial distinctions between hardwares? 
The simple fact is that there's nothing intrinsically special about being
the first SATA disk - especially if you really are wanting to boot off USB.
> 
> Yes, but that's not a lot of help when it's trying to read that
> partition on the wrong disk. Or when you can't get to menu.lst to
> correct the problem

pffft.  You can _always_ get to menu.lst to correct the problem.  You might
need to be an expert, but it's certainly possible.
> 
>> It's not that somebody came up with the idea to rename things just for
>> the heck of it. The kernel developers decided that all these devices
>> should be handled by the SCSI subsystem.
> 
> That's a wonderful idea. But the labels in /dev are nothing but text
> tags pointing to the real stuff. st.. would have worked. So would sD...
> or Sd.

For that matter so would hd, but what would it mean?  The whole point is
that those device names are _meaningless_, and so _shouldn't_ be tagged
with artificial and misleading distinctions.

> I did. They told me, essentially, "My way or Windows." I'm on their way,
> but whining...

LOL :-)  Been there, done that!

> After the install, all was well; the number one SATA was sda. Then I
> turned on the SCSI disk and rebooted -- now the SCSI disk was labeled
> sda, instead of the SATA. Then Ubuntu updated the kernel, and part of
> that involves rewriting parts of /boot/grub/menu.lst; and when it did
> that, the system wouldn't boot anymore -- I think it wrote the boot
> block on the SCSI disk. I don't know for sure, but it wouldn't boot into
> Linux.

And you couldn't fix that from a live CD?  I've managed to make systems
unbootable before, but you go to a live CD (the first time, I didn't even
use an Ubuntu one - I don't think they had a live CD then), and
run "grub-install".
-- 
derek