Label question...why does ufs label vanish on mount?

[Warren Block]

On Tue, 12 Oct 2010, Jeremy Chadwick wrote:

> On Tue, Oct 12, 2010 at 11:51:00AM -0700, Kevin Oberman wrote:
>> For some reason the /dev/ufs/label entry that geom creates for every UFS
>> formatted partition is deleted when the device is mounted.

Not here.

>> This is not the case for other file systems, though I have not tried 
>> them all. It makes the drive much harder to deal with when you have 
>> to keep track of which physical drive contains the labeled media. It 
>> is a particular issue for hald and the tools which depend on it.
>>
>> Is there a good reason for this odd behavior of UFS? If there is not a
>> good reason, could it be changed?
>
> I'm not sure if you're talking about "tunefs -L", or glabel(8).
>
> If you're talking about glabel(8): gotta read the man page carefully.
> There's two types of labels: "automatic" (glabel label) and "manual"
> (glabel create).
>
> "Automatic" labels are stored in the disk metadata, so they're retained
> after reboots + loaded during tasting, etc..  "Manual" labels are
> temporary, and have to be manually set every time the system starts.
>
> As for "tunefs -L" -- I never quite understood what this was for given
> glabel's existence.  I don't know if the two are synonymous in some way
> either.  I'm certain someone here can shed light on that association, if
> any at all.

glabel(8):

      This class also provides volume label detection for file systems.
      Those labels cannot be set with glabel, but must be set with the
      appropriate file system utility, e.g. for UFS the file system label
      is set with tunefs(8).

For reference:
http://www.wonkity.com/~wblock/docs/html/ahci.html