UUIDs on drives (was Hibernate on batery low)

[Smoot Carl-Mitchell]

On Thu, 2008-08-14 at 12:23 +0930, Brian Astill wrote:
> On Thursday 14 August 2008 09:47:49 Rashkae wrote:
> > I've never seen any problems
> > reported with the use of UUID that doesn't amount to old school
> > gurus not wanting to learn something different.
> 
> That's incorrect - unless you haven't been looking!
> If there is a key to unravel the info implicit in /dev/hdb3 
> (Primary partition on the Slave drive) from its UUID, would 
> someone please publish it.
> 
> Also, would someone please tell me how to construct a UUID for a 
> partition I have just created - short of rebooting and seeing if 
> I can identify it from fstab, assuming the partition is mounted.

You can display the UUID with the blkid program:

sudo blkid /dev/sda1
> 
> Why is a simple 8-digit code sufficient to uniquely identify a 
> vfat partition, eg "UUID=3FF4-3BE7  /media/hda1     vfat"
> whereas a Linux partition needs something HUGE
> UUID=d757b47c-5808-4271-a247-9df9072826de /media/hdb1     ext2

UUIDs are suppose to be universally unique.  Generating a random 16 byte
number is probably sufficient to make a UUID universally unique.  The
probability of a duplicate is 1 chance in 2**128 which is very unlikely.
4 bytes is not going to be universally unique.  I am not sure why vfat
partitions only have 4 byte UUIDs.  

-- 
Smoot Carl-Mitchell
System/Network Architect
smoot at tic.com
+1 480 922 7313
cell: +1 602 421 9005