Similar Experience/Forget Hardy

[Smoot Carl-Mitchell]

On Thu, 2008-06-12 at 10:16 -0300, Derek Broughton wrote:
> Avi Greenbury wrote:

> > For usb drives and the like, I like (and use) UUID.
> > For devices for which I know the /dev address, I use /dev.
> 
> The problem is, you don't "know" the /dev address.  You know it today, but
> there's no guarantee that changes made by either you (eg, deleting an
> unused partition) or a kernel update won't change that address in future.

/dev addresses are just a mapping to the filesystem for a character or
block device.  They can be put anywhere, but /dev is the historic place
where they reside in the filesystem tree. The names are even
configurable.  See manual page for udev which is the system that manages
the dev tree.  You will even see that /dev is a mount point to the
"udev" filesystem. This makes sense, since this part of the filesystem
tree gets recreated on every reboot and as Derek points out, there is no
guarantee the name mapping will be the same on the next reboot or if you
add or delete hardware, etc.

UUID and Label are just a way for abstracting the contents of a disk
away from the filesystem namspace. e.g. the dev name space is an
abstraction of the underlying hardware addresses to a name in the
filesystem name space.  UUID or Label abstract the filesystem name into
a more global or readable namespace.  UUID is preferred because the
namespace is suppose to be globally unique.

On a desktop system, I think UUID is a bit of overkill, but if you have
ever moved disks between servers, either physically or virtually on a
SAN fabric, it can be a lifesaver. It was a bit jarring to move to the
UUID system, but once I found out how the system works, I find it a lot
easier than doing things the old way.

If you want to see some of the gory details, take a look at
the /dev/disk tree.
-- 
Smoot Carl-Mitchell
System/Network Architect
smoot at tic.com
+1 480 922 7313
cell: +1 602 421 9005