latest feisty kernel can't see hda

Daniel Pittman daniel at
Sat Apr 28 08:12:16 UTC 2007

"Howard Coles Jr." <dhcolesj at> writes:
> On Friday 27 April 2007 01:49:48 pm John L Fjellstad wrote:
>> "Howard Coles" <dhcolesj at> writes:
>> >> You can also just use the /sbin/vol_id utility
>> >
>> > But, would that work if you can't boot the system?  I was trying to
>> > come up with a way to check UUID consistency with what udev was
>> > thinking verses what the fstab said, using a rescue cd/dvd.
>> Why wouldn't the vol_id utility work?  Isn't the UUID stored in the
>> filesystem itself.  According the manual page for vol_id, udev uses the
>> vol_id utility to figure out the UUID and label.
> I don't know, that's why I was asking.  I was assuming, and maybe
> wrongly so because I haven't looked at the man files for it, that it
> would look in the currently mounted root for that info, 

vol_id will give you the id of whatever block device or file you ask it
to identify.  It doesn't, in Unix tradition, do anything without

> and some distros (rightly in my opinion) don't use UUID.  

The distributions, and you, can use any label that the appropriate mount
binary can use to find and access the disk.

> I think, and its my opinion, UUIDs just confuse people, and they're no
> more secure that /dev/hda, especially considering everyone knows where
> on root to look!

The purpose of using a UUID is not security.  They are used for
convenience, specifically the convenience that they work reliably and
effectively on hardware that does not consistently assign the same
device name or number to an individual device.

That includes USB hardware on common platforms but also more exotic,
enterprise level equipment -- the same stuff that is gradually creeping
down in price and heading toward the mass market.

Using the device name *will* cause problems for Ubuntu -- the move to
libata in 2.6.20 has moved a large proportion of people from the
traditional /dev/hdX device names to /dev/sdX, with the added bonus of
SCSI probe ordering being less stable that traditional IDE.

Using a LABEL rather than a UUID to mount is possible but, especially
when vendors choose a stock label such as '/' for the disk, causes
serious problems if you attach a disk from one machine to another.

The filesystem UUID is the only consistent, reliable and reasonably
unique identifier available for the location of a Linux device or
partition at this point in the game.

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