zpool labelclear destroys GPT data

[Daniel O'Connor]

On 14/06/2013, at 17:05, Johan Hendriks <joh.hendriks at gmail.com> wrote:
>> Of course, zpool(8) will do exactly what you tell it to do. It does
>> not know about any partitioning schemes and assumes that the user
>> knows that using labelclear on a the whole disk will potentially
>> destroy all data on it including any partitioning information.
>> 
> Well as i found out, zpool(8) does not know what it clears. ! :D
> 
> I think an adjustment to the man page is in order here.
> The man page clearly state it removes ZFS labels, not GPT, gmirror and glabel labels.
> It should mention it will remove labels from the disk/device, and that it clears ALL labels.
> 
> If a user reads the man page it now looks save to use labelclear.
> I thougt that zpool would know if there was zpool label information on the disk, and if i a case there is no ZFS label information it will tell me that!
> In my case i did not loose anything, so no big deal but there will proberbly be someone who gets bitten by this.
> 
> A plus is that  i found a new way to clear my disks fast ! ;)


It only clears ZFS labels, just because GPT & gmirror information sits in a similar place doesn't make that incorrect.

You are saying the equivalent of..
Why does "dd if=/dev/zero of=/dev/da0" erase my whole disk, not just the first partition?

ie you are giving the tool bad options and then complaining when it doesn't do what you meant :)

Perhaps it should be modified to check if there is valid ZFS data there before proceeding (although that could be annoying unless there is a way to force it), and/or the man page could be amended to say it doesn't do any checks before erasing things.

--
Daniel O'Connor software and network engineer
for Genesis Software - http://www.gsoft.com.au
"The nice thing about standards is that there
are so many of them to choose from."
  -- Andrew Tanenbaum
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